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• get_or_create generic relations in Django & python debugging in general

  - by rabidpebble

  I ran the code to create the generically related objects from this demo: http://www.djangoproject.com/documentation/models/generic_relations/ Everything is good intially: >>> bacon.tags.create(tag="fatty") <TaggedItem: fatty> >>> tag, newtag = bacon.tags.get_or_create(tag="fatty") >>> tag <TaggedItem: fatty> >>> newtag False But then the use case that I'm interested in for my app: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome") Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 123, in get_or_create return self.get_query_set().get_or_create(**kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 343, in get_or_create raise e IntegrityError: app_taggeditem.content_type_id may not be NULL I tried a bunch of random things after looking at other code: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem) ValueError: Cannot assign "<class 'generics.app.models.TaggedItem'>": "TaggedItem.content_type" must be a "ContentType" instance. or: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem.content_type) InterfaceError: Error binding parameter 3 - probably unsupported type. etc. I'm sure somebody can give me the correct syntax, but the real problem here is that I have no idea what is going on. I have developed in strongly typed languages for over ten years (x86 assembly, C++ and C#) but am new to Python. I find it really difficult to follow what is going on in Python when things like this break. In the languages I mentioned previously it's fairly straightforward to figure things like this out -- check the method signature and check your parameters. Looking at the Django documentation for half an hour left me just as lost. Looking at the source for get_or_create(self, **kwargs) didn't help either since there is no method signature and the code appears very generic. A next step would be to debug the method and try to figure out what is happening, but this seems a bit extreme... I seem to be missing some fundamental operating principle here... what is it? How do I resolve issues like this on my own in the future?

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• PERL newbie : get a proper minimal debug_mode solution

  - by Michael Mao

  Hi all: I am learning PERL in a "head-first" manner. I am absolutely a newbie in this language: I am trying to have a debug_mode switch from CLI which can be used to control how my script works, by switching certain subroutines "on and off". And below is what I've got so far: #!/usr/bin/perl -s -w # purpose : make subroutine execution optional, # which is depending on a CLI switch flag use strict; use warnings; use constant DEBUG_VERBOSE => "v"; use constant DEBUG_SUPPRESS_ERROR_MSGS => "s"; use constant DEBUG_IGNORE_VALIDATION => "i"; use constant DEBUG_SETPPING_COMPUTATION => "c"; our ($debug_mode); mainMethod(); sub mainMethod # () { if(!$debug_mode) { print "debug_mode is OFF\n"; } elsif($debug_mode) { print "debug_mode is ON\n"; } else { print "OMG!\n"; exit -1; } checkArgv(); printErrorMsg("Error_Code_123", "Parsing Error at..."); verbose(); } sub checkArgv #() { print ("Number of ARGV : ".(1 + $#ARGV)."\n"); } sub printErrorMsg # ($error_code, $error_msg, ..) { if(defined($debug_mode) && !($debug_mode =~ DEBUG_SUPPRESS_ERROR_MSGS)) { print "You can only see me if -debug_mode is NOT set". " to DEBUG_SUPPRESS_ERROR_MSGS\n"; die("terminated prematurely...\n") and exit -1; } } sub verbose # () { if(defined($debug_mode) && ($debug_mode =~ DEBUG_VERBOSE)) { print "Blah blah blah...\n"; } } So far as I can tell, at least it works...: the -debug_mode switch doesn't interfere with normal ARGV the following commandlines work: ./optional.pl ./optional.pl -debug_mode ./optional.pl -debug_mode=v ./optional.pl -debug_mode=s However, I am puzzled when multiple debug_modes are "mixed", such as: ./optional.pl -debug_mode=sv ./optional.pl -debug_mode=vs I don't understand why the above lines of code "magically works". I see both of the "DEBUG_VERBOS" and "DEBUG_SUPPRESS_ERROR_MSGS" apply to the script, which is fine in this case. However, if there are some "conflicting" debug modes, I am not sure how to set the "precedence of debue_modes"? Also, I am not certain if my approach is good enough to Perlists and I hope I am getting my feet in the right direction. One biggest problem is that I now put if statements inside most of my subroutines for controlling their behavior under different modes. Is this okay? Is there a more elegant way? I know there must be a debug module from CPAN or elsewhere, but I wanna a real minimal solution that doesn't depend on any other module than the "default" And I cannot have any control on the environment where this script will be executed... Many thanks to the suggestions in advance.

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• ASP.NET MVC & EF4 Entity Framework - Are there any performance concerns in using the entities vs retrieving only the fields i need?

  - by Ant

  Lets say we have 3 tables, Users, Products, Purchases. There is a view that needs to display the purchases made by a user. I could lookup the data required by doing: from p in DBSet<Purchases>.Include("User").Include("Product") select p; However, I am concern that this may have a performance impact because it will retrieve the full objects. Alternatively, I could select only the fields i need: from p in DBSet<Purchases>.Include("User").Include("Product") select new SimplePurchaseInfo() { UserName = p.User.name, Userid = p.User.Id, ProductName = p.Product.Name ... etc }; So my question is: Whats the best practice in doing this? == EDIT Thanks for all the replies. [QUESTION 1]: I want to know whether all views should work with flat ViewModels with very specific data for that view, or should the ViewModels contain the entity objects. Real example: User reviews Products var query = from dr in productRepository.FindAllReviews() where dr.User.UserId = 'userid' select dr; string sql = ((ObjectQuery)query).ToTraceString(); SELECT [Extent1].[ProductId] AS [ProductId], [Extent1].[Comment] AS [Comment], [Extent1].[CreatedTime] AS [CreatedTime], [Extent1].[Id] AS [Id], [Extent1].[Rating] AS [Rating], [Extent1].[UserId] AS [UserId], [Extent3].[CreatedTime] AS [CreatedTime1], [Extent3].[CreatorId] AS [CreatorId], [Extent3].[Description] AS [Description], [Extent3].[Id] AS [Id1], [Extent3].[Name] AS [Name], [Extent3].[Price] AS [Price], [Extent3].[Rating] AS [Rating1], [Extent3].[ShopId] AS [ShopId], [Extent3].[Thumbnail] AS [Thumbnail], [Extent3].[Creator_UserId] AS [Creator_UserId], [Extent4].[Comment] AS [Comment1], [Extent4].[DateCreated] AS [DateCreated], [Extent4].[DateLastActivity] AS [DateLastActivity], [Extent4].[DateLastLogin] AS [DateLastLogin], [Extent4].[DateLastPasswordChange] AS [DateLastPasswordChange], [Extent4].[Email] AS [Email], [Extent4].[Enabled] AS [Enabled], [Extent4].[PasswordHash] AS [PasswordHash], [Extent4].[PasswordSalt] AS [PasswordSalt], [Extent4].[ScreenName] AS [ScreenName], [Extent4].[Thumbnail] AS [Thumbnail1], [Extent4].[UserId] AS [UserId1], [Extent4].[UserName] AS [UserName] FROM [ProductReviews] AS [Extent1] INNER JOIN [Users] AS [Extent2] ON [Extent1].[UserId] = [Extent2].[UserId] LEFT OUTER JOIN [Products] AS [Extent3] ON [Extent1].[ProductId] = [Extent3].[Id] LEFT OUTER JOIN [Users] AS [Extent4] ON [Extent1].[UserId] = [Extent4].[UserId] WHERE N'615005822' = [Extent2].[UserId] or from d in productRepository.FindAllProducts() from dr in d.ProductReviews where dr.User.UserId == 'userid' orderby dr.CreatedTime select new ProductReviewInfo() { product = new SimpleProductInfo() { Id = d.Id, Name = d.Name, Thumbnail = d.Thumbnail, Rating = d.Rating }, Rating = dr.Rating, Comment = dr.Comment, UserId = dr.UserId, UserScreenName = dr.User.ScreenName, UserThumbnail = dr.User.Thumbnail, CreateTime = dr.CreatedTime }; SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[Thumbnail] AS [Thumbnail], [Extent1].[Rating] AS [Rating], [Extent2].[Rating] AS [Rating1], [Extent2].[Comment] AS [Comment], [Extent2].[UserId] AS [UserId], [Extent4].[ScreenName] AS [ScreenName], [Extent4].[Thumbnail] AS [Thumbnail1], [Extent2].[CreatedTime] AS [CreatedTime] FROM [Products] AS [Extent1] INNER JOIN [ProductReviews] AS [Extent2] ON [Extent1].[Id] = [Extent2].[ProductId] INNER JOIN [Users] AS [Extent3] ON [Extent2].[UserId] = [Extent3].[UserId] LEFT OUTER JOIN [Users] AS [Extent4] ON [Extent2].[UserId] = [Extent4].[UserId] WHERE N'userid' = [Extent3].[UserId] ORDER BY [Extent2].[CreatedTime] ASC [QUESTION 2]: Whats with the ugly outer joins?

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• Does this MSDN article violate MVVM?

  - by rasx

  This may be old news but back in March 2009, this article, “Model-View-ViewModel In Silverlight 2 Apps,” has a code sample that includes DataServiceEntityBase: // COPIED FROM SILVERLIGHTCONTRIB Project for simplicity /// <summary> /// Base class for DataService Data Contract classes to implement /// base functionality that is needed like INotifyPropertyChanged. /// Add the base class in the partial class to add the implementation. /// </summary> public abstract class DataServiceEntityBase : INotifyPropertyChanged { /// <summary> /// The handler for the registrants of the interface's event /// </summary> PropertyChangedEventHandler _propertyChangedHandler; /// <summary> /// Allow inheritors to fire the event more simply. /// </summary> /// <param name="propertyName"></param> protected void FirePropertyChanged(string propertyName) { if (_propertyChangedHandler != null) { _propertyChangedHandler(this, new PropertyChangedEventArgs(propertyName)); } } #region INotifyPropertyChanged Members /// <summary> /// The interface used to notify changes on the entity. /// </summary> event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged { add { _propertyChangedHandler += value; } remove { _propertyChangedHandler -= value; } } #endregion What this class implies is that the developer intends to bind visuals directly to data (yes, a ViewModel is used but it defines an ObservableCollection of data objects). Is this design diverging too far from the guidance of MVVM? Now I can see some of the reasons Why would we go this way: what we can do with DataServiceEntityBase is this sort of thing (which is intimate with the Entity Framework): // Partial Method to support the INotifyPropertyChanged interface public partial class Game : DataServiceEntityBase { #region Partial Method INotifyPropertyChanged Implementation // Override the Changed partial methods to implement the // INotifyPropertyChanged interface // This helps with the Model implementation to be a mostly // DataBound implementation partial void OnDeveloperChanged() { base.FirePropertyChanged("Developer"); } partial void OnGenreChanged() { base.FirePropertyChanged("Genre"); } partial void OnListPriceChanged() { base.FirePropertyChanged("ListPrice"); } partial void OnListPriceCurrencyChanged() { base.FirePropertyChanged("ListPriceCurrency"); } partial void OnPlayerInfoChanged() { base.FirePropertyChanged("PlayerInfo"); } partial void OnProductDescriptionChanged() { base.FirePropertyChanged("ProductDescription"); } partial void OnProductIDChanged() { base.FirePropertyChanged("ProductID"); } partial void OnProductImageUrlChanged() { base.FirePropertyChanged("ProductImageUrl"); } partial void OnProductNameChanged() { base.FirePropertyChanged("ProductName"); } partial void OnProductTypeIDChanged() { base.FirePropertyChanged("ProductTypeID"); } partial void OnPublisherChanged() { base.FirePropertyChanged("Publisher"); } partial void OnRatingChanged() { base.FirePropertyChanged("Rating"); } partial void OnRatingUrlChanged() { base.FirePropertyChanged("RatingUrl"); } partial void OnReleaseDateChanged() { base.FirePropertyChanged("ReleaseDate"); } partial void OnSystemNameChanged() { base.FirePropertyChanged("SystemName"); } #endregion } Of course MSDN code can seen as “toy code” for educational purposes but is anyone doing anything like this in the real world of Silverlight development?

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• What are the basics of dealing with user input events in Android?

  - by user279112

  Hello. I thought I had understood this question, but something is quite wrong here. When the user (me, so far) tries to press keys, nothing really happens, and I am having a lot of trouble understanding what it is that I've missed. Consider this before I present some code to help clarify my problem: I am using Android's Lunar Lander example to make my first "real" Android program. In that example, of course, there exist a class LunarView, and class nested therein LunarThread. In my code the equivalents of these classes are Graphics and GraphicsThread, respectively. Also I can make sprite animations in 2D just fine on Android. I have a Player class, and let's say GraphicsThread has a Player member referred to as "player". This class has four coordinates - x1, y1, x2, and y2 - and they define a rectangle in which the sprite is to be drawn. I've worked it out so that I can handle that perfectly. Whenever the doDraw(Canvas canvas) method is invoked, it'll just look at the values of those coordinates and draw the sprite accordingly. Now let's say - and this isn't really what I'm trying to do with the program - I'm trying to make the program where all it does is display the Player sprite at one location of the screen UNTIL the FIRST time the user presses the Dpad's left button. Then the location will be changed to another set position on the screen, and the sprite will be drawn at that position for the rest of the program invariably. Also note that the GraphicsThread member in Graphics is called "thread", and that the SurfaceHolder member in GraphicsThread is called "mSurfaceHolder". So consider this method in class Graphics: @Override public boolean onKeyDown(int keyCode, KeyEvent msg) { return thread.keyDownHandler(keyCode, msg); } Also please consider this method in class GraphicsThread: boolean keyDownHandler(int keyCode, KeyEvent msg) { synchronized (mSurfaceHolder) { if (keyCode == KeyEvent.KEYCODE_DPAD_LEFT) { player.x1 = 100; player.y1 = 100; player.x2 = 120; player.y2 = 150; } } return true; } Now then assuming that player's coordinates start off as (200, 200, 220, 250), why won't he do anything different when I press Dpad: Left? Thanks!

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• Dealing with missing messages in JavaScript when using BOSH

  - by JamieD

  We recently went into private beta on our flagship product and had a small launch event. Unfortunately the venue had a terrible wireless connection and packets were being dropped left right and centre causing havoc with out system, basically it wasn't able to work at all! Luckily we were able to switch to a different network and rescue the demo. This highlighted something that I knew was already an issue but hadn't appreciated quite how much of an issue it could be. Our system relies heavily on BOSH and has a rather large JavaScript code base which now works rather well under good network conditions. However we need to make it work well under bad network conditions as well. Due to the way that XMPP works, a fire and forget system, it's not easy to tell if a message you sent, or were supposed to receive, was actually sent or received. For instance, we have an offer system, one user will send an offer to another over BOSH. When this message is received by the server a message is published to the offering users offers_sent PEP node and a similar message to the receiving users offers_received PEP node. While the sending user is able to tell if their offer was send (relatively) easily, if the notification to the receiving user is never received that user will never know it missed a message. A little about out JavaScript setup, it has 4 main layers: StropheJS An MVC framework for dealing with low level tasks and to build on top of An application layer which contains the app logic routes, controllers models etc. as well as a browser cache of the model data A UI layer that receives events and publishes events to and from the application layer One way to solve the missing messages issue would be to periodically check the PEP nodes for new data that the browser doesn't know about. If a new message was discovered the browsers cache would be invalidated and all new data would be requested from the server. I'm not sure this is the best way to go and it also doesn't cover all situations. We certainly don't want to get into the situation where we are sending messages to confirm the previous message was received at it's destination as this would double the network traffic. With the number of real time websites growing daily this is an issue that must have been encountered by other developers, it would be interesting to see how it's been solved by others. As far as I can see there are two situations in which messages go missing: On poor connections messages are not sent or received due to the packets being dropped Involving navigating between pages, a message is received by the browser but is not fully processed and stored in the local cache before the page is unloaded. Or a message is added to the send queue but never sent before the page is unloaded I suspect the hardest issue to solve will be number 2. Any thoughts on the subject would be much appreciated.

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• What to Return? Error String, Bool with Error String Out, or Void with Exception

  - by Ranger Pretzel

  I spend most of my time in C# and am trying to figure out which is the best practice for handling an exception and cleanly return an error message from a called method back to the calling method. For example, here is some ActiveDirectory authentication code. Please imagine this Method as part of a Class (and not just a standalone function.) bool IsUserAuthenticated(string domain, string user, string pass, out errStr) { bool authentic = false; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; // No exception thrown? We must be good, then. authentic = true; } catch (Exception e) { errStr = e.Message().ToString(); } return authentic; } The advantages of doing it this way are a clear YES or NO that you can embed right in your If-Then-Else statement. The downside is that it also requires the person using the method to supply a string to get the Error back (if any.) I guess I could overload this method with the same parameters minus the "out errStr", but ignoring the error seems like a bad idea since there can be many reasons for such a failure... Alternatively, I could write a method that returns an Error String (instead of using "out errStr") in which a returned empty string means that the user authenticated fine. string AuthenticateUser(string domain, string user, string pass) { string errStr = ""; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } catch (Exception e) { errStr = e.Message().ToString(); } return errStr; } But this seems like a "weak" way of doing things. Or should I just make my method "void" and just not handle the exception so that it gets passed back to the calling function? void AuthenticateUser(string domain, string user, string pass) { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } This seems the most sane to me (for some reason). Yet at the same time, the only real advantage of wrapping those 2 lines over just typing those 2 lines everywhere I need to authenticate is that I don't need to include the "LDAP://" string. The downside with this way of doing it is that the user has to put this method in a try-catch block. Thoughts? Is there another way of doing this that I'm not thinking of?

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• How to force VS 2010 to skip "builds" of projects which haven't changed?

  - by Ladislav Mrnka

  Our product's solution has more than 100+ projects (500+ksloc of production code). Most of them are C# projects but we also have few using C++/CLI to bridge communication with native code. Rebuilding the whole solution takes several minutes. That's fine. If I want to rebuilt the solution I expect that it will really take some time. What is not fine is time needed to build solution after full rebuild. Imagine I used full rebuild and know without doing any changes to to the solution I press Build (F6 or Ctrl+Shift+B). Why it takes 35s if there was no change? In output I see that it started "building" of each project - it doesn't perform real build but it does something which consumes significant amount of time. That 35s delay is pain in the ass. Yes I can improve the time by not using build solution but only build project (Shift+F6). If I run build project on particular test project I'm currently working on it will take "only" 8+s. It requires me to run project build on correct project (the test project to ensure dependent tested code is build as well). At least ReSharper test runner correctly recognizes that only this single project must be build and rerunning test usually contains only 8+s compilation. My current coding Kata is: don't touch Ctrl+Shift+B. The test project build will take 8s even if I don't do any changes. The reason why it takes 8s is because it also "builds" dependencies = in my case it "builds" more than 20 projects but I made changes only to unit test or single dependency! I don't want it to touch other projects. Is there a way to simply tell VS to build only projects where some changes were done and projects which are dependent on changed ones (preferably this part as another build option)? I worry you will tell me that it is exactly what VS is doing but in MS way ... I want to improve my TDD experience and reduce the time of compilation (in TDD the compilation can happen twice per minute). To make this even more frustrated I'm working in a team where most of developers used to work on Java projects prior to joining this one. So you can imagine how they are pissed off when they must use VS in contrast to full incremental compilation in Java. I don't require incremental compilation of classes. I expect working incremental compilation of solutions. Especially in product like VS 2010 Ultimate which costs several thousands dollars. I really don't want to get answers like: Make a separate solution Unload projects you don't need etc. I can read those answers here. Those are not acceptable solutions. We're not paying for VS to do such compromises.

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• Gap appears between navigation bar and view after rotating & tab switching

  - by Bogatyr

  My iphone application is showing strange behavior when rotating: a gap appears between the navigation title and content view inside a tab bar view (details on how to reproduce are below). I've created a tiny test case that exhibits the same problem: a custom root UIViewController, which creates and displays a UITabBarController programmatically, which has two tabs: 1) plain UIViewController, and 2) UINavigationController created programmatically with a single plain UIViewController content view. The complete code for the application is in the root controller's viewDidLoad (every "*VC" class is a totally vanilla UIViewController subclass with XIB for user interface from XCode, with only the view background color changed to clearly identify each view, nothing else). Here's the viewDidLoad code, and the shouldAutorotateToInterfaceOrientation code, this code is the entire application basically: - (void)viewDidLoad { [super viewDidLoad]; FirstVC *fvc = [[FirstVC alloc] initWithNibName:@"FirstVC" bundle:nil]; NavContentsVC *ncvc = [[NavContentsVC alloc] initWithNibName:@"NavContentsVC" bundle:nil]; UINavigationController *svc = [[UINavigationController alloc] initWithRootViewController:ncvc]; NSMutableArray *localControllersArray = [[NSMutableArray alloc] initWithCapacity:2]; [localControllersArray addObject:fvc]; [localControllersArray addObject:svc]; fvc.title = @"FirstVC-Title"; ncvc.title = @"NavContents-Title"; UITabBarController *tbc = [[UITabBarController alloc] init]; tbc.view.frame = CGRectMake(0, 0, 320, 460); [tbc setViewControllers:localControllersArray]; [self.view addSubview:tbc.view]; [localControllersArray release]; [ncvc release]; [svc release]; [fvc release]; } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return YES; } Here's how to reproduce the problem: 1) start application 2) rotate device (happens in simulator, too) to landscape (UITabBar properly rotates) 3) click on tab 2 4) rotate device to portrait -- notice gap of root view controller's background color of about 10 pixels high beneath the Navigation title bar and the Navigation content view. 5) click tab 1 6) click tab 2 And the gap is gone! From my real application, I see that the gap remains during all VC push and pops while the NavigationController tab is active. Switching away to a different tab and back to the Nav tab clears up the gap. What am I doing wrong? I'm running on SDK 3.1.3, this happens both on the simulator and on the device. Except for this particular sequence, everything seems to work fine. Help!

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• I've got my 2D/3D conversion working perfectly, how to do perspective

  - by user346992

  Although the context of this question is about making a 2d/3d game, the problem i have boils down to some math. Although its a 2.5D world, lets pretend its just 2d for this question. // xa: x-accent, the x coordinate of the projection // mapP: a coordinate on a map which need to be projected // _Dist_ values are constants for the projection, choosing them correctly will result in i.e. an isometric projection xa = mapP.x * xDistX + mapP.y * xDistY; ya = mapP.x * yDistX + mapP.y * yDistY; xDistX and yDistX determine the angle of the x-axis, and xDistY and yDistY determine the angle of the y-axis on the projection (and also the size of the grid, but lets assume this is 1-pixel for simplicity). x-axis-angle = atan(yDistX/xDistX) y-axis-angle = atan(yDistY/yDistY) a "normal" coordinate system like this --------------- x | | | | | y has values like this: xDistX = 1; yDistX = 0; xDistY = 0; YDistY = 1; So every step in x direction will result on the projection to 1 pixel to the right end 0 pixels down. Every step in the y direction of the projection will result in 0 steps to the right and 1 pixel down. When choosing the correct xDistX, yDistX, xDistY, yDistY, you can project any trimetric or dimetric system (which is why i chose this). So far so good, when this is drawn everything turns out okay. If "my system" and mindset are clear, lets move on to perspective. I wanted to add some perspective to this grid so i added some extra's like this: camera = new MapPoint(60, 60); dx = mapP.x - camera.x; // delta x dy = mapP.y - camera.y; // delta y dist = Math.sqrt(dx * dx + dy * dy); // dist is the distance to the camera, Pythagoras etc.. all objects must be in front of the camera fac = 1 - dist / 100; // this formula determines the amount of perspective xa = fac * (mapP.x * xDistX + mapP.y * xDistY) ; ya = fac * (mapP.x * yDistX + mapP.y * yDistY ); Now the real hard part... what if you got a (xa,ya) point on the projection and want to calculate the original point (x,y). For the first case (without perspective) i did find the inverse function, but how can this be done for the formula with the perspective. May math skills are not quite up to the challenge to solve this. ( I vaguely remember from a long time ago mathematica could create inverse function for some special cases... could it solve this problem? Could someone maybe try?)

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• Joomla - Force File Download / CSV Export

  - by lautaro.dragan

  I'm in need of help... this is my first time asking a question in SO, so please be kind :) I'm trying to force-download a file from php, so when the user hits a certain button, he gets a file download. The file is a csv (email, username) of all registered users. I decided to add this button to the admin users screen, as you can see in this screenshot. So I added the following code to the addToolbar function in administrator/components/com_users/views/users/view.html.php: JToolBarHelper::custom('users.export', 'export.png', 'export_f2.png', 'Exportar', false); This button is mapped to the following function in the com_users\controller\users.php controller: public function exportAllUsers() { ob_end_clean(); $app = JFactory::getApplication(); header("Content-type: text/csv"); header("Content-Disposition: attachment; filename=ideary_users.csv"); header("Pragma: no-cache"); header("Expires: 0"); echo "email,name\n"; $model = $this->getModel("Users"); $users = $model->getAllUsers(); foreach ($users as $user) { echo $user->email . ", " . ucwords(trim($user->name)) . "\r\n"; } $app->close(); } Now, this is actually working perfectly fine. The issue here is that after I download a file, if I hit any button in the admin that causes a POST, instead of it performing the action it should, it just downloads the file over again! For example: I hit the "Export" button "users.csv" downloads Then, I hit the "search" button "users.csv" downloads... what the hell? I'm guessing that when I hit the export button, a JS gets called and sets a form's action attribute to an URL... and expects a response or something, and then other button's are prevented from re-setting the form's action attribute. I can't think of any real solution for this, but I'd rather avoid hacks if possible. So, what would be the standard, elegant solution that joomla offers in this case?

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• How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

  - by Ian Ringrose

  We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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• Bullet indents in PowerPoint 2007 compatibility mode via .NET interop issue

  - by L. Shaydariv

  Hello. I've got a really difficult bug and I can't see the fix. The subject drives me insane for real for a long time. Let's consider the following scenario: 1) There is a PowerPoint 2003 presentation. It contains the only slide and the only shape, but the shape contains a text frame including a bulleted list with a random textual representation structure. 2) There is a requirement to get bullet indents for every bulletted paragraph using PowerPoint 2007. I can satisfy the requirement opening the presentation in the compatibility mode and applying the following VBA script: With ActivePresentation Dim sl As Slide: Set sl = .Slides(1) Dim sh As Shape: Set sh = sl.Shapes(1) Dim i As Integer For i = 1 To sh.TextFrame.TextRange.Paragraphs.Count Dim para As TextRange: Set para = sh.TextFrame.TextRange.Paragraphs(i, 1) Debug.Print para.Text; para.indentLevel, sh.TextFrame.Ruler.Levels(para.indentLevel).FirstMargin Next i End With that produces the following output: A 1 0 B 1 0 C 2 24 D 3 60 E 5 132 Obviously, everything is perfect indeed: it has shown the proper list item text, list item level and its bullet indent. But I can't see the way of how I can reach the same result using C#. Let's add a COM-reference to Microsoft.Office.Interop.PowerPoint 2.9.0.0 (taken from MSPPT.OLB, MS Office 12): // presentation = ...("presentation.ppt")... // a PowerPoint 2003 presentation Slide slide = presentation.Slides[1]; Shape shape = slide.Shapes[1]; for (int i = 1; i<=shape.TextFrame.TextRange.Paragraphs(-1, -1).Count; i++) { TextRange paragraph = shape.TextFrame.TextRange.Paragraphs(i, 1); Console.WriteLine("{0} {1} {2}", paragraph.Text, paragraph.IndentLevel, shape.TextFrame.Ruler.Levels[paragraph.IndentLevel].FirstMargin); } Oh, man... What's it? I've got problems here. First, the paragraph.Text value is trimmed until the '\r' character is found (however paragraph.Text[0] really returns the first character O_o). But it's ok, I can shut my eyes to this. But... But, second, I can't understand why the first margins are always zero and it does not matter which level they belong to. They are always zero in the compatibility mode... It's hard to believe it... :) So is there any way to fix it or just to find a workaround? I'd like to accept any help regarding to the solution of the subject. I can't even find any article related to the issue. :( Probably you have ever been face to face with it... Or is it just a bug with no fix and must it be reported to Microsoft? Thanks you.

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• A Question about using jython when run a receving socket in python

  - by abusemind

  Hi, I have not a lot of knowledge of python and network programming. Currently I am trying to implement a simple application which can receive a text message sent by the user, fetch some information from the google search api, and return the results via text message to the user. This application will continue to listening to the users messages and reply immediately. How I get the text short message sent by the user? It's a program named fetion from the mobile supplier in China. The client side fetion, just like a instant communication tool, can send/receive messages to/from other people who are using mobile to receive/send SMS. I am using a open source python program that simulates the fetion program. So basically I can use this python program to communate with others who using cell phone via SMS. My core program is based on java, so I need to take this python program into java environment. I am using jython, and now I am available to send messages to users by some lines of java codes. But the real question is the process of receving from users via SMS. In python code, a new thread is created to continuously listen to the user. It should be OK in Python, but when I run the similar process in Jython, the following exception occurs: Exception in thread Thread:Traceback (most recent call last): File "D:\jython2.5.1\Lib\threading.py", line 178, in _Thread__bootstrap self.run() File "<iostream>", line 1389, in run File "<iostream>", line 1207, in receive File "<iostream>", line 1207, in receive File "<iostream>", line 150, in recv File "D:\jython2.5.1\Lib\select.py", line 223, in native_select pobj.register(fd, POLLIN) File "D:\jython2.5.1\Lib\select.py", line 104, in register raise _map_exception(jlx) error: (20000, 'socket must be in non-blocking mode') The line 150 in the python code is as follows: def recv(self,timeout=False): if self.login_type == "HTTP": time.sleep(10) return self.get_offline_msg() pass else: if timeout: infd,outfd,errfd = select([self.__sock,],[],[],timeout)//<---line 150 here else: infd,outfd,errfd = select([self.__sock,],[],[]) if len(infd) != 0: ret = self.__tcp_recv() num = len(ret) d_print(('num',),locals()) if num == 0: return ret if num == 1: return ret[0] for r in ret: self.queue.put(r) d_print(('r',),locals()) if not self.queue.empty(): return self.queue.get() else: return "TimeOut" Because of I am not very familiar with python, especially the socket part, and also new in Jython use, I really need your help or only advice or explanation. Thank you very much!

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• c#: Clean way to fit a collection into a multidimensional array?

  - by Rosarch

  I have an ICollection<MapNode>. Each MapNode has a Position attribute, which is a Point. I want to sort these points first by Y value, then by X value, and put them in a multidimensional array (MapNode[,]). The collection would look something like this: (30, 20) (20, 20) (20, 30) (30, 10) (30, 30) (20, 10) And the final product: (20, 10) (20, 20) (20, 30) (30, 10) (30, 20) (30, 30) Here is the code I have come up with to do it. Is this hideously unreadable? I feel like it's more hacky than it needs to be. private Map createWorldPathNodes() { ICollection<MapNode> points = new HashSet<MapNode>(); Rectangle worldBounds = WorldQueryUtils.WorldBounds(); for (float x = worldBounds.Left; x < worldBounds.Right; x += PATH_NODE_CHUNK_SIZE) { for (float y = worldBounds.Y; y > worldBounds.Height; y -= PATH_NODE_CHUNK_SIZE) { // default is that everywhere is navigable; // a different function is responsible for determining the real value points.Add(new MapNode(true, new Point((int)x, (int)y))); } } int distinctXValues = points.Select(node => node.Position.X).Distinct().Count(); int distinctYValues = points.Select(node => node.Position.Y).Distinct().Count(); IList<MapNode[]> mapNodeRowsToAdd = new List<MapNode[]>(); while (points.Count > 0) // every iteration will take a row out of points { // get all the nodes with the greatest Y value currently in the collection int currentMaxY = points.Select(node => node.Position.Y).Max(); ICollection<MapNode> ythRow = points.Where(node => node.Position.Y == currentMaxY).ToList(); // remove these nodes from the pool we're picking from points = points.Where(node => ! ythRow.Contains(node)).ToList(); // ToList() is just so it is still a collection // put the nodes with max y value in the array, sorting by X value mapNodeRowsToAdd.Add(ythRow.OrderByDescending(node => node.Position.X).ToArray()); } MapNode[,] mapNodes = new MapNode[distinctXValues, distinctYValues]; int xValuesAdded = 0; int yValuesAdded = 0; foreach (MapNode[] mapNodeRow in mapNodeRowsToAdd) { xValuesAdded = 0; foreach (MapNode node in mapNodeRow) { // [y, x] may seem backwards, but mapNodes[y] == the yth row mapNodes[yValuesAdded, xValuesAdded] = node; xValuesAdded++; } yValuesAdded++; } return pathNodes; } The above function seems to work pretty well, but it hasn't been subjected to bulletproof testing yet.

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• php page navigation by serial number

  - by ilnur777

  Can anyone help in this php page navigation script switch on counting normal serial number? In this script there is a var called "page_id" - I want this var to store the real page link by order like 0, 1, 2, 3, 4, 5 ... $records = 34; // total records $pagerecord = 10; // count records to display per page if($records<=$pagerecord) return; $imax = (int)($records/$pagerecord); if ($records%$pagerecord>0)$imax=$imax+1; if($activepage == ''){ $for_start=$imax; $activepage = $imax-1; } $next = $activepage - 1; if ($next<0){$next=0;} $prev = $activepage + 1; if ($prev>=$imax){$prev=$imax-1;} $end = 0; $start = $imax; if($activepage >= 0){ $for_start = $activepage + $rad + 1; if($for_start<$rad*2+1)$for_start = $rad*2+1; if($for_start>=$imax){ $for_start=$imax; } } if($activepage < $imax-1){ $str .= ' <a href="?domain='.$domain_name.'&page='.($start-1).'&page_id=xxx"><<< End</a> <a href="?domain='.$domain_name.'&page='.$prev.'&page_id=xxx">< Forward</a> '; } $meter = $rad*2+1; for($i=$for_start-1; $i>-1; $i--){ $meter--; $line = ''; if ($i>0)$line = ""; if($i<>$activepage){ $str .= "<a href='?domain=".$domain_name."&page=".$i."&page_id=xxx'>".($i)."</a> ".$line." "; } else { $str .= " <b class='current_page'>".($i)."</b> ".$line." "; } if($meter=='0'){ break; } } if($activepage > 0){ $str .= " <a href='?domain=".$domain_name."&page=".$next."&page_id=xxx'>Back ></a> <a href='?domain=".$domain_name."&page=".($end)."&page_id=xxx'>Start >>></a> "; } return $str; Really need help with this stuff! Thanks in advance!

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• Is there any reasonable use of a function returning an anonymous struct?

  - by Akanksh

  Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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• Visual Studio soft-crashing when encountering XAML Errors in initialize.

  - by Aren

  I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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• What is the Fastest Way to Check for a Keyword in a List of Keywords in Delphi?

  - by lkessler

  I have a small list of keywords. What I'd really like to do is akin to: case MyKeyword of 'CHIL': (code for CHIL); 'HUSB': (code for HUSB); 'WIFE': (code for WIFE); 'SEX': (code for SEX); else (code for everything else); end; Unfortunately the CASE statement can't be used like that for strings. I could use the straight IF THEN ELSE IF construct, e.g.: if MyKeyword = 'CHIL' then (code for CHIL) else if MyKeyword = 'HUSB' then (code for HUSB) else if MyKeyword = 'WIFE' then (code for WIFE) else if MyKeyword = 'SEX' then (code for SEX) else (code for everything else); but I've heard this is relatively inefficient. What I had been doing instead is: P := pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX '); case P of 1: (code for CHIL); 6: (code for HUSB); 11: (code for WIFE); 17: (code for SEX); else (code for everything else); end; This, of course is not the best programming style, but it works fine for me and up to now didn't make a difference. So what is the best way to rewrite this in Delphi so that it is both simple, understandable but also fast? (For reference, I am using Delphi 2009 with Unicode strings.) Followup: Toby recommended I simply use the If Then Else construct. Looking back at my examples that used a CASE statement, I can see how that is a viable answer. Unfortunately, my inclusion of the CASE inadvertently hid my real question. I actually don't care which keyword it is. That is just a bonus if the particular method can identify it like the POS method can. What I need is to know whether or not the keyword is in the set of keywords. So really I want to know if there is anything better than: if pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX ') > 0 then The If Then Else equivalent does not seem better in this case being: if (MyKeyword = 'CHIL') or (MyKeyword = 'HUSB') or (MyKeyword = 'WIFE') or (MyKeyword = 'SEX') then In Barry's comment to Kornel's question, he mentions the TDictionary Generic. I've not yet picked up on the new Generic collections and it looks like I should delve into them. My question here would be whether they are built for efficiency and how would using TDictionary compare in looks and in speed to the above two lines? In later profiling, I have found that the concatenation of strings as in: (' ' + MyKeyword + ' ') is VERY expensive time-wise and should be avoided whenever possible. Almost any other solution is better than doing this.

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• Any tool(s) for knowing the layout (segments) of running process in Windows?

  - by claws

  I've always been curious about How exactly the process looks in memory? What are the different segments(parts) in it? How exactly will be the program (on the disk) & process (in the memory) are related? My previous question: http://stackoverflow.com/questions/1966920/more-info-on-memory-layout-of-an-executable-program-process In my quest, I finally found a answer. I found this excellent article that cleared most of my queries: http://www.linuxforums.org/articles/understanding-elf-using-readelf-and-objdump_125.html In the above article, author shows how to get different segments of the process (LINUX) & he compares it with its corresponding ELF file. I'm quoting this section here: Courious to see the real layout of process segment? We can use /proc//maps file to reveal it. is the PID of the process we want to observe. Before we move on, we have a small problem here. Our test program runs so fast that it ends before we can even dump the related /proc entry. I use gdb to solve this. You can use another trick such as inserting sleep() before it calls return(). In a console (or a terminal emulator such as xterm) do: $ gdb test (gdb) b main Breakpoint 1 at 0x8048376 (gdb) r Breakpoint 1, 0x08048376 in main () Hold right here, open another console and find out the PID of program "test". If you want the quick way, type: $ cat /proc/`pgrep test`/maps You will see an output like below (you might get different output): [1] 0039d000-003b2000 r-xp 00000000 16:41 1080084 /lib/ld-2.3.3.so [2] 003b2000-003b3000 r--p 00014000 16:41 1080084 /lib/ld-2.3.3.so [3] 003b3000-003b4000 rw-p 00015000 16:41 1080084 /lib/ld-2.3.3.so [4] 003b6000-004cb000 r-xp 00000000 16:41 1080085 /lib/tls/libc-2.3.3.so [5] 004cb000-004cd000 r--p 00115000 16:41 1080085 /lib/tls/libc-2.3.3.so [6] 004cd000-004cf000 rw-p 00117000 16:41 1080085 /lib/tls/libc-2.3.3.so [7] 004cf000-004d1000 rw-p 004cf000 00:00 0 [8] 08048000-08049000 r-xp 00000000 16:06 66970 /tmp/test [9] 08049000-0804a000 rw-p 00000000 16:06 66970 /tmp/test [10] b7fec000-b7fed000 rw-p b7fec000 00:00 0 [11] bffeb000-c0000000 rw-p bffeb000 00:00 0 [12] ffffe000-fffff000 ---p 00000000 00:00 0 Note: I add number on each line as reference. Back to gdb, type: (gdb) q So, in total, we see 12 segment (also known as Virtual Memory Area--VMA). But I want to know about Windows Process & PE file format. Any tool(s) for getting the layout (segments) of running process in Windows? Any other good resources for learning more on this subject? EDIT: Are there any good articles which shows the mapping between PE file sections & VA segments?

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• Good working habits to observe in project development?

  - by Will Marcouiller

  As my development experience grows, I see fit to stick to best practices from here and there to build somehow my own working practices while observing the conventions, etc. I'm currently working on a project which my goals is to graduate the security access model from an environment's Active Directory to another environment's automatically. I don't know for any of you, but as far as I'm concerned, I meet some real difficulties sticking to only one way, then develop. I mean, I learn something new everyday while visiting SO, and recently wanted to get acquainted with generics. On the other hand, I better know the Façade pattern which proved to be very practical in transactional programming in process systems. This seems to be less practical for desktop application as there are plenty of variables to consider in a desktop application that you don't have to care in transactional programming, as you're playing only with information data. As for my current project, I have: Groups; Organizational Units; Users. Which are all considered an entry in the Active Directory. This points out to be a good candidate for generics, as also approached this way by Bart de Smett's Linq to AD on CodePlex. He has a DirectorySource<T>, and to manage let's say groups, then he instantiate a source with the proper type: var groups = new DirectorySource<Group>(); This seems to be very a good way of doing. Despite, I seem to go from one pattern to another and I don't seem to be able to strictly stick to one. While I'm aware that one must not stay with only one way of doing, since each pattern statisfies certain advantages, while also illustrating disadvantages under some usage conditions, I seem to want to develop with both patterns having a singleton Façade class with the underlying factories which represent the sub systems: GroupsFactory; UsersFactory; OrganizationalUnitsFactory. Each of the factories offers the possible operations for their respective entity (group, user, OU). To make a very long story short, I often have plenty of ideas while developping and this causes me some trouble, as I go from an idea to another feeling completely lost after a while. Yet I understand the advantages and disavantages, I have no trouble choosing from one pattern to another depending on the situation. Nevertheless, when it comes to programming itself, if I'm not part of a team, I feel sometimes like I can't do anything good. That is, because I can't stand not doing something "perfect" the first time. The role I play within the project is both: the project manager and the programmer. I am more comfortable in the project manager role, architectural role, analytical role than the developer's. Has any of you some good habbits to observe in project development? Thanks to you all! =)

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• Powershell $LastExitCode=0 but $?=False . Redirecting stderr to stdout gives NativeCommandError

  - by Colonel Panic

  Can anyone explain Powershell's surprising behaviour in the second example below? First, a example of sane behaviour: PS C:\> & cmd /c "echo Hello from standard error 1>&2"; echo "`$LastExitCode=$LastExitCode and `$?=$?" Hello from standard error $LastExitCode=0 and $?=True No surprises. I print a message to standard error (using cmd's echo). I inspect the variables $? and $LastExitCode. They equal to True and 0 respectively, as expected. However, if I ask Powershell to redirect standard error to standard output over the first command, I get a NativeCommandError: PS C:\> & cmd /c "echo Hello from standard error 1>&2" 2>&1; echo "`$LastExitCode=$LastExitCode and `$?=$?" cmd.exe : Hello from standard error At line:1 char:4 + cmd <<<< /c "echo Hello from standard error 1>&2" 2>&1; echo "`$LastExitCode=$LastExitCode and `$?=$?" + CategoryInfo : NotSpecified: (Hello from standard error :String) [], RemoteException + FullyQualifiedErrorId : NativeCommandError $LastExitCode=0 and $?=False My first question, why the NativeCommandError ? Secondly, why is $? False when cmd ran successfully and $LastExitCode is 0? Powershell's docs about_Automatic_Variables don't explicitly define $?. I always supposed it is True if and only if $LastExitCode is 0 but my example contradicts that. Here's how I came across this behaviour in the real-world (simplified). It really is FUBAR. I was calling one Powershell script from another. The inner script: cmd /c "echo Hello from standard error 1>&2" if (! $?) { echo "Job failed. Sending email.." exit 1 } # do something else Running this simply .\job.ps1, it works fine, no email is sent. However, I was calling it from another Powershell script, logging to a file .\job.ps1 2>&1 > log.txt. In this case, an email is sent! Here, the act of observing a phenomenon changes its outcome. This feels like quantum physics rather than scripting! [Interestingly: .\job.ps1 2>&1 may or not blow up depending on where you run it]

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• The question about the basics of LINQ to SQL

  - by Alex

  I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer LINQ gets all customers from the database ("SELECT * FROM Customers"), moves them to the Customers array and then makes a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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• Android: Memory leak due to AsyncTask

  - by Manu

  Hello, I'm stuck with a memory leak that I cannot fix. I identified where it occurs, using the MemoryAnalizer but I vainly struggle to get rid of it. Here is the code: public class MyActivity extends Activity implements SurfaceHolder.Callback { ... Camera.PictureCallback mPictureCallbackJpeg = new Camera.PictureCallback() { public void onPictureTaken(byte[] data, Camera c) { try { // log the action Log.e(getClass().getSimpleName(), "PICTURE CALLBACK JPEG: data.length = " + data); // Show the ProgressDialog on this thread pd = ProgressDialog.show(MyActivity.this, "", "Préparation", true, false); // Start a new thread that will manage the capture new ManageCaptureTask().execute(data, c); } catch(Exception e){ AlertDialog.Builder dialog = new AlertDialog.Builder(MyActivity.this); ... dialog.create().show(); } } class ManageCaptureTask extends AsyncTask<Object, Void, Boolean> { protected Boolean doInBackground(Object... args) { Boolean isSuccess = false; // initialize the bitmap before the capture ((myApp) getApplication()).setBitmapX(null); try{ // Check if it is a real device or an emulator TelephonyManager telmgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); String deviceID = telmgr.getDeviceId(); boolean isEmulator = "000000000000000".equalsIgnoreCase(deviceID); // get the bitmap if (isEmulator) { ((myApp) getApplication()).setBitmapX(BitmapFactory.decodeFile(imageFileName)); } else { ((myApp) getApplication()).setBitmapX(BitmapFactory.decodeByteArray((byte[]) args[0], 0, ((byte[])args[0]).length)); } ((myApp) getApplication()).setImageForDB(ImageTools.resizeBmp(((myApp) getApplication()).getBmp())); // convert the bitmap into a grayscale image and display it in the preview ((myApp) getApplication()).setImage(makeGrayScale()); isSuccess = true; } catch (Exception connEx){ errorMessageFromBkgndThread = getString(R.string.errcapture); } return isSuccess; } protected void onPostExecute(Boolean result) { // Pass the result data back to the main activity if (MyActivity.this.pd != null) { MyActivity.this.pd.dismiss(); } if (result){ ((ImageView) findViewById(R.id.apercu)).setImageBitmap(((myApp) getApplication()).getBmp()); ((myApp) getApplication()).setBitmapX(null); } else{ // there was an error ErrAlert(); } } } }; private void ErrAlert(){ // notify the user about the error AlertDialog.Builder dialog = new AlertDialog.Builder(this); ... dialog.create().show(); } } MemoryAnalyzer indicated the memory leak at: ((myApp) getApplication()).setBitmapX(BitmapFactory.decodeByteArray((byte[]) args[0], 0, ((byte[])args[0]).length)); I am grateful for any suggestion, thank you in advance.

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• Newbie's problems with MySQL and php

  - by Mirage81

  I'm a real newbie with php and MySQL. Now I'm working on the following code which should search the database for eg. all the Lennons living in Liverpool. 1) How should I modify "get.php" to get the text "no results" to appear if there are no search results. 2) How should I modify "index.php" to get the option values (city and lastname) straight from the database instead of having to type them one by one? 3) Am I using mysql_real_escape_string the right way? 4) Any other mistakes in the code? index.php: <form action="get.php" method="post"> <p> <select name="city"> <option value="Birmingham">Birmingham</option> <option value="Liverpool">Liverpool</option> <option value="London">London</option> </select> </p> <p> <select name="lastname"> <option value="Lennon">Lennon</option> <option value="McCartney">McCartney</option> <option value="Osbourne">Osbourne</option> </select> </p> <p> <input value="Search" type="submit"> </p> </form> get.php: <?php $city = $_POST['city']; $lastname = $_POST['lastname']; $conn = mysql_connect('localhost', 'user', 'password'); mysql_select_db("database", $conn) or die("connection failed"); $query = "SELECT * FROM users WHERE city = '$city' AND lastname = '$lastname'"; $result = mysql_query($query, $conn); $city = mysql_real_escape_string($_POST['city']); $lastname = mysql_real_escape_string($_POST['lastname']); echo $rowcount; while ($row = mysql_fetch_row($result)) { if ($rowcount == '0') echo 'no results'; else { echo '<b>City: </b>'.htmlspecialchars($row[0]).'<br />'; echo '<b>Last name: </b>'.htmlspecialchars($row[1]).'<br />'; echo '<b>Information: </b>'.htmlspecialchars($row[2]); } } mysql_close($conn);

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