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• Modifying existing object attributes in Core Data after the fact

  - by glorifiedHacker

  In a previous question, I was looking for an alternative to modifying how "no date" was being stored in the date attribute of my NSManagedObject subclass. Previously, I had assigned nil to that attribute when a user didn't assign a date. In order to address sorting issues when using NSFetchedResultsController, I have decided to assign [NSDate distantFuture] to the date attribute when a user doesn't assign a date. However, given that this app is already in the wild, I need to update the Core Data store such that any existing nil date values are changed to [NSDate distantFuture]. What is the best way to make this change? The first thing that comes to mind is to iterate through all of the objects in the store in an array and change any nil values that are found. This could be limited to a one-time event by checking against a user defaults key that indicates whether this upgrade has been performed. Is there a way that I can do this with Core Data versioning instead? Or another method that doesn't involve me writing throw-away code?

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• How to build a Django form which requires a delay to be re-submitted ?

  - by pierre-guillaume-degans

  Hey, In order to avoid spamming, I would like to add a waiting time to re-submit a form (i.e. the user should wait a few seconds to submit the form, except the first time that this form is submitted). To do that, I added a timestamp to my form (and a security_hash field containing the timestamp plus the settings.SECRET_KEY which ensures that the timestamp is not fiddled with). This look like: class MyForm(forms.Form): timestamp = forms.IntegerField(widget=forms.HiddenInput) security_hash = forms.CharField(min_length=40, max_length=40, widget=forms.HiddenInput) # + some other fields.. # + methods to build the hash and to clean the timestamp... # (it is based on django.contrib.comments.forms.CommentSecurityForm) def clean_timestamp(self): """Make sure the delay is over (5 seconds).""" ts = self.cleaned_data["timestamp"] if not time.time() - ts > 5: raise forms.ValidationError("Timestamp check failed") return ts # etc... This works fine. However there is still an issue: the timestamp is checked the first time the form is submitted by the user, and I need to avoid this. Any idea to fix it ? Thank you ! :-)

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• Eclipselink: Create objects from JOIN query

  - by Raven

  Hi, I have a SQL query SELECT * FROM Thing AS a JOIN Thing_Property AS b ON a.id=b.Thing_ID JOIN Property AS c ON b.properties_ID = c.id JOIN Item AS d ON c.item_ID = d.id ORDER BY a.name, d.name and I Eclipselink to create my object model with it. Here is the model: @SuppressWarnings("serial") @Entity public class Thing implements Serializable { @Id @GeneratedValue(strategy = GenerationType.TABLE) private int id; private String name; @OneToMany(cascade=CascadeType.ALL) @PrivateOwned private List<Property> properties = new ArrayList<Property>(); ... // getter and setter following here } public class Property implements Serializable { @Id @GeneratedValue(strategy = GenerationType.TABLE) private int id; @OneToOne private Item item; private String value; ... // getter and setter following here } public class Item implements Serializable { @Id @GeneratedValue(strategy = GenerationType.TABLE) private int id; private String name; .... // getter and setter following here } // Code end but I can not figure out, how to make Eclipselink create the model from that query. Can you help?

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• IDE framework for a dynamic language?

  - by Kevin Reid

  Let's say I have a super-wonderful new programming language, and I want there to be an IDE for it. What IDE platform/framework could I use to get this done efficiently? I mean things like: Collection of files in a project, searching them, tabbed/split editors etc. — the basics. Syntax highlighting and auto-indent/reformatting. Providing the user interface for code completion — hit tab, get a list (I'll have to implement the necessary partial evaluation myself (it's a dynamic language)). This is the feature I'm most wishing for. Built-in parser framework which is good at recovering from the sort of syntax errors occurring in code that is in the middle of being edited would be helpful. In-editor annotation of syntax/runtime error locations fed back from the language runtime. REPL (interactive evaluator) interaction with the same completion as in the editor. This system should be Linux/Mac/Windows cross-platform (in that priority order). Being implemented in Java (or rather, accepting language plugins written in Java) is possibly useful, but anything else is worth a try too.

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• What's the most DRY-appropriate way to execute an SQL command?

  - by Sean U

  I'm looking to figure out the best way to execute a database query using the least amount of boilerplate code. The method suggested in the SqlCommand documentation: private static void ReadOrderData(string connectionString) { string queryString = "SELECT OrderID, CustomerID FROM dbo.Orders;"; using (SqlConnection connection = new SqlConnection(connectionString)) { SqlCommand command = new SqlCommand(queryString, connection); connection.Open(); SqlDataReader reader = command.ExecuteReader(); try { while (reader.Read()) { Console.WriteLine(String.Format("{0}, {1}", reader[0], reader[1])); } } finally { reader.Close(); } } } mostly consists of code that would have to be repeated in every method that interacts with the database. I'm already in the habit of factoring out the establishment of a connection, which would yield code more like the following. (I'm also modifying it so that it returns data, in order to make the example a bit less trivial.) private SQLConnection CreateConnection() { var connection = new SqlConnection(_connectionString); connection.Open(); return connection; } private List<int> ReadOrderData() { using(var connection = CreateConnection()) using(var command = connection.CreateCommand()) { command.CommandText = "SELECT OrderID FROM dbo.Orders;"; using(var reader = command.ExecuteReader()) { var results = new List<int>(); while(reader.Read()) results.Add(reader.GetInt32(0)); return results; } } } That's an improvement, but there's still enough boilerplate to nag at me. Can this be reduced further? In particular, I'd like to do something about the first two lines of the procedure. I don't feel like the method should be in charge of creating the SqlCommand. It's a tiny piece of repetition as it is in the example, but it seems to grow if transactions are being managed manually or timeouts are being altered or anything like that.

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• OpenGL pixels drawn with each horizontal pair swapped

  - by Tim Kane

  I'm somewhat new to OpenGL though I'm fairly sure my problem lies in the pixel format being used, or how my texture is being generated... I'm drawing a texture onto a flat 2D quad using a 16bit RGB5_A1 pixel format, though I don't make use of any alpha at this stage. The problem I'm having is that each pair of horizontal pixel values have been swapped. That is... if the pixels positions should be in this order (assume 8x2 image) 0 1 2 3 4 5 6 7 they are instead drawn as 1 0 3 2 5 4 7 6 Or, more clearly from this image (below). Left is what I get... Right is what I should get. . The question is... How have I ended up with this? Is there something wrong with the pixel format? Unlikely since the colours all appear correct, and I would expect all kinds of nasty if it were down to endian-ness. Suggestions greatly appreciated. Update: Turns out the problem was in my source renderer. Interestingly, I've avoided the problem entirely by using 32-bit textures (haven't tried 24-bit at this point).

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• Fixing parent controller's elements after screen orientation

  - by Jonas Anderson

  I have a tab bar application with mixed orientation support for only some views. One of the child view controller shown from one of the tab's navigation controller is displayed only in Landscape mode. In order to accomplish this, I've done the view transformation for the child view as suggested here: Is there a documented way to set the iPhone orientation? The only problem I'm seeing is that after I've performed the orientation adjustment for the child controller and then readjusted orientation back to normal on its dismissal, the contents of the (parent) navigation controller is still shown with Landscape mode dimensions despite the navigation controller reporting the correct value for the interfaceOrientation. How do I ensure that view's size is reset to match the orientation without hardcoding screen dimensions? I have the following in the root navigation controller's viewWillAppear (invoked after the child controller is dismissed): - (void)viewWillAppear:(BOOL)animated { NSLog(@"viewFrame: (%2f, %2f), width: %2f, height: %2f\n", self.view.frame.origin.x, self.view.frame.origin.y, self.view.frame.size.width, self.view.frame.size.height); // Frame values are (0, 0) for (x,y) width: 320, height: 367 before I // displayed child controller. // Frame values are (0,0) width: 480, height: 219 after returning from child // controller -- still has the landscape dimensions NSLog(@"orientation: %d", self.interfaceOrientation); // reports portrait as expected } I've tried to invoke 'layoutIfNeeded' as well as 'setNeedsDisplay' on the view but neither of them bring the view contents into the correct display. Any suggestions would be greatly appreciated.

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• iPhone TabbarController Switch Transition

  - by user269737

  I've implemented gestures (touchBegan-moved-ended) in order to allow for swiping through my tabs. It works. I'd like to add a slide-from-left and slide-from-right transition. It would be better if it could be part of the gesture if statement which tells me if the swipe is towards the right of left. Since I determine which tab is displayed from that, I could show that specific transition along with the new tab. So my question is this: what's the simplest way to simplement a slide transition at a specific instance. I don't want it to be for the whole tabbarcontrol since this is specifically for the swiping. Thanks for the help, much appreciated. For clarification purposes, this is snippet shows how I'm switching tabs: if(abs(diffx / diffy) > 2.5 && abs(diffx) > HORIZ_SWIPE_DRAG_MIN) { // It appears to be a swipe. if(isProcessingListMove) { // ignore move, we're currently processing the swipe return; } if (mystartTouchPosition.x < currentTouchPosition.x) { isProcessingListMove = YES; self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:0]; return; } else { isProcessingListMove = YES; self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:1 ]; return; }

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• Technology and language for a stable Digital Audio Workstation development

  - by Kill KRT

  Hi, I'm designing a cross platform (Windows/Linux/OS X) application, something like a digital audio workstation. I'd like to create a software where users have a fully featured sequencer (multiple tracks with automation) and where it is possible to create instruments using a visual language (as Pure Data/Max MSP). Ehm... I know that I've already posted a question about a related issue... But in order to decide which technology I should use, I think I'd better to make more investigation. I'm a quite experted user of audio trackers (Renoise, Protracker,...) and sequencers (FL Studio, Cubase 5), but I didn't ever try to develop even a basic audio tracker. I know just the basic theory of mixing sound and know how basically a DSP works. My questions are: Where I can find a good tutorial/guide/book about this issue? Do you think using C# (with NAudio) could dramatically reduce performance? I know C++ would be the best choice, but I find C# so elegant and easy to build and port, while C++ is so powerful and fast, but there are too #define and bad things for my taste! ;-) Thank you.

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• How to keep your unit test Arrange step simple and still guarantee DDD invariants ?

  - by ian31

  DDD recommends that the domain objects should be in a valid state at any time. Aggregate roots are responsible for guaranteeing the invariants and Factories for assembling objects with all the required parts so that they are initialized in a valid state. However this seems to complicate the task of creating simple, isolated unit tests a lot. Let's assume we have a BookRepository that contains Books. A Book has : an Author a Category a list of Bookstores you can find the book in These are required attributes : a book has to have an author, a category and at least a book store you can buy the book from. There's likely to be a BookFactory since it is quite a complex object, and the Factory will initialize the Book with at least all the mentioned attributes. Now we want to unit test a method of the BookRepository that returns all the Books. To test if the method returns the books, we have to set up a test context (the Arrange step in AAA terms) where some Books are already in the Repository. If the only tool at our disposal to create Book objects is the Factory, the unit test now also uses and is dependent on the Factory and inderectly on Category, Author and Store since we need those objects to build up a Book and then place it in the test context. Would you consider this is a dependency in the same way that in a Service unit test we would be dependent on, say, a Repository that the Service would call ? How would you solve the problem of having to re-create a whole cluster of objects in order to be able to test a simple thing ? How would you break that dependency and get rid of all these attributes we don't need in our test ? By using mocks or stubs ? If you mock up things a Repository contains, what kind of mock/stubs would you use as opposed to when you mock up something the object under test talks to or consumes ?

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• Wordpress loop not showing 'else' when no posts exist

  - by Reuben

  When no posts exist I'm used to seeing the message after the else, and I'm not sure why it's not showing it now? Code: <?php $args = array( 'post_type' => 'event', 'posts_per_page' => 1, 'post_status' => 'future', 'order' => 'ASC' ); $loop = new WP_Query( $args ); if ( have_posts() ) : while ( $loop->have_posts() ) : $loop->the_post(); ?> <div class="event_preview_title"><?php the_title(); ?></div> <div class="event_details"> <div class="event_date"><?php the_time('m/d/y'); ?></div> <div class="event_time"><?php the_time('g:i A'); ?></div> </div> <?php the_post_thumbnail( array(65,65) ); ?> <a class="clickthrough" href="<?php bloginfo('wpurl'); ?>/events"></a> <?php endwhile; else: ?> <p>Bluebird Books may be coming soon to a neighborhood near you!<br /> We are currently on hiatus planning our next season's schedule. New tour dates will be posted to this page once confirmed. Meanwhile, inquiries about appearances and programs are welcomed! If you are interested in having Bluebird visit your business, school, or special event, please contact us.</p> <?php endif; ?> Thanks!

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• Ideas for storing e-mail messages in a Delphi client server application

  - by user193655

  There are many suggestions here and there for storing e-mail messages. Somehow what I am doing is writing an Outlook addin to send emails from inbox/sent folders directly to my application. So only what is really interesting is saved. And I decide where to save it. Imagine this case: I recieve an email from a customer. It's up to me to decide whether I should save it on the customer or on the order 24 that that customer did. So this is why I am doing the add in, and not some automatic storing of emails = noise after some time. This said, how to store the emails? For the emails that I recieve or send through Outlook the idea could be save the whole file in a blob field (so the eml file), may be I can save also other info (like the subject) in another text field. But the problem comes when I write an email from my application. In this case I am not generating an eml file, I send through MAPI data to Outlook to compose an email that I will send with Outlook (so in this case I cannot save the eml), or I directly send it with Indy. Also in this case I don't have the eml file... One idea could be that the all the emails that I auto compose have a special flag that the Add in recognises and therefore when I send the mail it is stored back to the DB. So in this case I can save the eml also of the mails I sent from my application. May you comment?

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• Website Live Chat Script - Interface With Windows Live Messenger?

  - by Sootah

  Hello again fellow StackOverflow users! What I am looking for currently is your opinions on the what the best live chat script would be for my website. I'd be using this on both my local computer repair (which I've not really set up yet) company's site, as well as my other technical support site that is geared more towards showing people how to fix whatever problem they have themselves. It'll be a little bit before I launch it on either site, as I need to find a good design for my local computer repair company's site, as well as redesign TweaksForGeeks.com's layout so that it's more magazine like. (If you have any suggestions on good Wordpress templates for these, that'd also be swell. :) ) Features I'd like for the live chat script to have: (if possible) Real-time posting of messages (or as close to real time as possible) Integration into my Windows Live Messenger account - By this I mean it'd be handy if instead of me having to man a separate open browser window and constantly check it for new messages, it'd be much more convenient if it would instead just allow me to receive and respond to messages via my Windows Live account the same way I'd chat with any other person on my contact list. Sound notification of new messages when the chat isn't the focused window - In the event that using Windows Messenger isn't possible then I'd need it to notify me upon receipt of a new message. Recording of chat transcripts - This is a MUST HAVE Easy customization - I'll likely want to modify how it looks and whatnot, in addition to the fact that I'm going to set it up so that the chat transcripts can be posted to my site easily in order to be useful to my other visitors later on. With all that in mind, what is available out there? I've not really researched this at all yet; aside from doing a cursory search just before I decided to ask my StackOverflow brothers. As always, thank you! -Sootah

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• MS Query returns data inside itself but does not export it to Excel

  - by kappa

  Hi, I'm having a strange problem with Excel and MS Query: I'm using MS Query to run a T-SQL query against a Microsoft SQL Server 2000 and return the results to Excel. To do this, I open Excel, go to Data - Import external data - New database query, select my data source, paste the SQL script in MS Query and click File - Return data to Microsoft Office Excel, leaving all the query options to their defaults. This works fine for many other Excel files, but this time although MS Query shows the correct data when I paste the SQL script, after returning to Excel all I get is the query name in the upper left cell, with no data returned. I fear the cause could be the SQL script, as it contains some advanced functions like union all, UDFs and variables. Here's the script: declare @date smalldatetime set @date = dateadd(day, datediff(day, 0, getdate()), 0) select [date], sum([hours]) as [hours] from ( select [date], [hours] from [server].[dbo].[udf] (84, '2010-01-01', @date) union all select [date], [hours] from [server].[dbo].[udf] (89, '2010-01-01', @date) union all select [date], [hours] from [server].[dbo].[udf] (93, '2010-01-01', @date) ) as [a] group by [date] order by [date] asc I can't get rid of the UDF as inside them are done advanced groupings involving cursors and temporary tables, nor I can remove the variable as the UDF won't accept dateadd(day, datediff(day, 0, getdate()), 0) as parameter. Any ideas? Thanks in advance, Andrea.

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• Can shared memory be read and validated without mutexes?

  - by Bribles

  On Linux I'm using shmget and shmat to setup a shared memory segment that one process will write to and one or more processes will read from. The data that is being shared is a few megabytes in size and when updated is completely rewritten; it's never partially updated. I have my shared memory segment laid out as follows: ------------------------- | t0 | actual data | t1 | ------------------------- where t0 and t1 are copies of the time when the writer began its update (with enough precision such that successive updates are guaranteed to have differing times). The writer first writes to t1, then copies in the data, then writes to t0. The reader on the other hand reads t0, then the data, then t1. If the reader gets the same value for t0 and t1 then it considers the data consistent and valid, if not, it tries again. Does this procedure ensure that if the reader thinks the data is valid then it actually is? Do I need to worry about out-of-order execution (OOE)? If so, would the reader using memcpy to get the entire shared memory segment overcome the OOE issues on the reader side? (This assumes that memcpy performs it's copy linearly and ascending through the address space. Is that assumption valid?)

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• [C++] Multiple inclusion in multiple files

  - by Amumu

  Hi everyone, I am making a small game. In BattleRecord.h: #ifndef _CHARACTER_H_ #define _CHARACTER_H_ #include "Character.h" #endif class BattleRecord { public: Character Attacker; Character Defender; Status status; int DamageDealt; int GoldEarned; int ExpGained; }; In Character.h: #ifndef _EQUIPMENT_H_ #define _EQUIPMENT_H_ #include "Equipment.h" #endif class BattleRecord; class Character { BattleRecord AttackEnemy(Character &Enemy); } In BattleRecord.h: #ifndef _CHARACTER_H_ #define _CHARACTEr_H_ #include "Character.h" #endif #ifndef _BATLE_RECORD_H_ #define _BATLE_RECORD_H_ #include "BattleRecord.h" #endif class GUI { public: //GUI Methods, and two of these: void ViewStats(Character &Player); void Report(BattleRecord Record) } The problem here is, my Character.h and BattleRecord.h need to include each other, and this definitely will cause multiple redefinition problem. Therefore, I used forward declaration in Character.h by adding: class BattleRecord; The problem is sovled. But then, the GUI.h needs BattleRecord.h again for reporting the battle, so I have to include BattleRecord.h into the GUI.h. I also have to include the Character.h in order to pass into the ViewStat function. I got error and stuck with this up to this piont.

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• Parsing a JSON feed from YQL using jQuery

  - by Keith

  I am using YQL's query.multi to grab multiple feeds so I can parse a single JSON feed with jQuery and reduce the number of connections I'm making. In order to parse a single feed, I need to be able to check the type of result (photo, item, entry, etc) so I can pull out items in specific ways. Because of the way the items are nested within the JSON feed, I'm not sure the best way to loop through the results and check the type and then loop through the items to display them. Here is a YQL (http://developer.yahoo.com/yql/console/) query.multi example and you can see three different result types (entry, photo, and item) and then the items nested within them: select * from query.multi where queries= "select * from twitter.user.timeline where id='twitter'; select * from flickr.photos.search where has_geo='true' and text='san francisco'; select * from delicious.feeds.popular" or here is the JSON feed itself: http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20query.multi%20where%20queries%3D%22select%20*%20from%20flickr.photos.search%20where%20user_id%3D'23433895%40N00'%3Bselect%20*%20from%20delicious.feeds%20where%20username%3D'keith.muth'%3Bselect%20*%20from%20twitter.user.timeline%20where%20id%3D'keithmuth'%22&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=

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• VirtualHosting doesn't work. Logs me in through previous session

  - by Pablo

  When I log in with one browser session, I have to log in, but when I open another session it has automatically logged me in (as if I've picked up session 1), this does not happen if I use http://192.168.0.9:9070 It forces me to log in each time. So I know the application is working, it's just the proxy server that seems to apply the loging to each session (from http://icerap.limeo.com). # ************************************************************************ # Start of My stuff <<<------------------------------------------------------ # ************************************************************************ #<Proxy *> #Order Deny,Allow #Deny from all #Allow from 192.168.0 #</Proxy> # blog <VirtualHost *:80> ServerName icerap.limeo.com ProxyPass / http://192.168.0.9:9070/ ProxyPassReverse / http://192.168.0.9:9070/ </VirtualHost> # www <VirtualHost *:80> ServerName helpdesk.limeo.com ProxyPass / http://192.168.0.9:9055/ ProxyPassReverse / http://192.168.0.9:9055/ </VirtualHost> # blog <VirtualHost *:80> ServerName IceCake.limeo.com ProxyPass / http://192.168.0.9:9000/ ProxyPassReverse / http://192.168.0.9:9000/ </VirtualHost> # End of Limeo stuff <<<------------------------------------------------------ # ************************************************************************

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• Targetting x86 vs AnyCPU when building for 64 bit window OSes

  - by Mr Roys

  I have an existing C# application written for .NET 2.0 and targetting AnyCPU at the moment. It currently references some third party .NET DLLs which I don't have the source for (and I'm not sure if they were built for x86, x64 or AnyCPU). If I want to run my application specifically on a 64 bit Windows OS, which platform should I target in order for my app to run without errors? My understanding at the moment is to target: x86: If at least one third party .NET dll is built for x86 or use p/Invoke to interface with Win32 DLLs. Application will run in 32 bit mode on both 32 bit and 64 bit OSes. x64: If all third party .NET dlls are already built for x64 or AnyCPU. Application will only run in 64 bit OSes. AnyCPU: If all third party .NET dlls are already built for AnyCPU. Application will run in 32 bit mode on 32 bit OSes and 64 bit on 64 bit OSes. Also, am I right to believe that while targetting AnyCPU will generate no errors when building a application referencing third party x86 .NET DLLs, the application will throw a runtime exception when it tries to load these DLLs when it runs on a 64 bit OS. Hence, as long as one of my third party DLLs is doing p/Invoke or are x86, I can only target x86 for this application?

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• Extended SurfaceView onDraw never called

  - by Gab Royer

  Hi, I'm trying to modify the SurfaceView I use for doing a camera preview in order to display an overlaying square. However, the onDraw method of the extended SurfaceView is never called. Here is the source : public class CameraPreviewView extends SurfaceView { protected final Paint rectanglePaint = new Paint(); public CameraPreviewView(Context context, AttributeSet attrs) { super(context, attrs); rectanglePaint.setARGB(255, 200, 0, 0); rectanglePaint.setStyle(Paint.Style.FILL); rectanglePaint.setStrokeWidth(2); } @Override protected void onDraw(Canvas canvas){ canvas.drawRect(new Rect(10,10,200,200), rectanglePaint); Log.w(this.getClass().getName(), "On Draw Called"); } } public class CameraPreview extends Activity implements SurfaceHolder.Callback{ private SurfaceHolder holder; private Camera camera; @Override protected void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); // We remove the status bar, title bar and make the application fullscreen requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); // We set the content view to be the layout we made setContentView(R.layout.camera_preview); // We register the activity to handle the callbacks of the SurfaceView CameraPreviewView surfaceView = (CameraPreviewView) findViewById(R.id.camera_surface); holder = surfaceView.getHolder(); holder.addCallback(this); holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); } public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { Camera.Parameters params = camera.getParameters(); params.setPreviewSize(width, height); camera.setParameters(params); try { camera.setPreviewDisplay(holder); } catch (IOException e) { e.printStackTrace(); } camera.startPreview(); } public void surfaceCreated(SurfaceHolder holder) { camera = Camera.open(); } public void surfaceDestroyed(SurfaceHolder holder) { camera.stopPreview(); camera.release(); } }

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• Hierarchical/Nested Database Structure for Comments

  - by Stephen Melrose

  Hi, I'm trying to figure out the best approach for a database schema for comments. The problem I'm having is that the comments system will need to allow nested/hierarchical comments, and I'm not sure how to design this out properly. My requirements are, Comments can be made on comments, so I need to store the tree hierarchy I need to be able to query the comments in the tree hierarchy order, but efficiently, preferably in a fast single query, but I don't know if this is possible I'd need to make some wierd queries, e.g. pull out the latest 5 root comments, and a maximum of 3 children for each one of those I read an article on the MySQL website on this very subject, http://dev.mysql.com/tech-resources/articles/hierarchical-data.html The "Nested Set Model" in theory sounds like it will do what I need, except I'm worried about querying the thing, and also inserting. If this is the right approach, How would I do my 3rd requirement above? If I have 2000 comments, and I add a new sub-comment on the first comment, that will be a LOT of updating to do. This doesn't seem right to me? Or is there a better approach for the type of data I'm wanting to store and query? Thank you

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• How do I ensure that a regex does not match an empty string?

  - by Dancrumb

  I'm using the Jison parser generator for Javascript and am having problems with my language specification. The program I'm writing will be a calculator that can handle feet, inches and sixteenths. In order to do this, I have the following specification: %% ([0-9]+\s*"'")?\s*([0-9]+\s*"\"")?\s*([0-9]+\s*"s")? {return 'FIS';} [0-9]+("."[0-9]+)?\b {return 'NUMBER';} \s+ {/* skip whitespace */} "*" {return '*';} "/" {return '/';} "-" {return '-';} "+" {return '+';} "(" {return '(';} ")" {return ')';} <<EOF>> {return 'EOF';} Most of these lines come from a basic calculator specification. I simply added the first line. The regex correctly matches feet, inch, sixteenths, such as 6'4" (six feet, 4 inches) or 4"5s (4 inches, 5 sixteenths) with any kind of whitespace between the numbers and indicators. The problem is that the regex also matches a null string. As a result, the lexical analysis always records a FIS at the start of the line and then the parsing fails. Here is my question: is there a way to modify this regex to guarantee that it will only match a non-zero length string?

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• Query broke down and left me stranded in the woods

  - by user1290323

  I am trying to execute a query that deletes all files from the images table that do not exist in the filters tables. I am skipping 3,500 of the latest files in the database as to sort of "Trim" the table back to 3,500 + "X" amount of records in the filters table. The filters table holds markers for the file, as well as the file id used in the images table. The code will run on a cron job. My Code: $sql = mysql_query("SELECT * FROM `images` ORDER BY `id` DESC") or die(mysql_error()); while($row = mysql_fetch_array($sql)){ $id = $row['id']; $file = $row['url']; $getId = mysql_query("SELECT `id` FROM `filter` WHERE `img_id` = '".$id."'") or die(mysql_error()); if(mysql_num_rows($getId) == 0){ $IdQue[] = $id; $FileQue[] = $file; } } for($i=3500; $i<$x; $i++){ mysql_query("DELETE FROM `images` WHERE id='".$IdQue[$i]."' LIMIT 1") or die("line 18".mysql_error()); unlink($FileQue[$i]) or die("file Not deleted"); } echo ($i-3500)." files deleted."; Output: 0 files deleted. Database contents: images table: 10,000 rows filters table: 63 rows Amount of rows in filters table that contain an images table id: 63 Execution time of php script: 4 seconds +/- 0.5 second Relevant DB structure TABLE: images id url etc... TABLE: filter id img_id (CONTAINS ID FROM images table) etc...

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• Is this a variation of the traveling salesman problem?

  - by Ville Koskinen

  I'm interested in a function of two word lists, which would return an order agnostic edit distance between them. That is, the arguments would be two lists of (let's say space delimited) words and return value would be the minimum sum of the edit (or Levenshtein) distances of the words in the lists. Distance between "cat rat bat" and "rat bat cat" would be 0. Distance between "cat rat bat" and "fat had bad" would be the same as distance between "rat bat cat" and "had fat bad", 4. In the case the number of words in the lists are not the same, the shorter list would be padded with 0-length words. My intuition (which hasn't been nurtured with computer science classes) does not find any other solution than to use brute force: |had|fat|bad| a solution ---+---+---+---+ +---+---+---+ cat| 2 | 1 | 2 | | | 1 | | ---+---+---+---+ +---+---+---+ rat| 2 | 1 | 2 | | 3 | | | ---+---+---+---+ +---+---+---+ bat| 2 | 1 | 1 | | | | 4 | ---+---+---+---+ +---+---+---+ Starting from the first row, pick a column and go to the next rows without ever revisiting a column you have already visited. Do this over and over again until you've tried all combinations. To me this sounds a bit like the traveling salesman problem. Is it, and how would you solve my particular problem?

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• Reordering methods in ComImport interfaces throws COMException (0x80041001)

  - by Ohad Schneider

  Consider the following code for COM interop with internet shortcuts: [ComImport] [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] [Guid("CABB0DA0-DA57-11CF-9974-0020AFD79762")] public interface IUniformResourceLocatorW { void SetUrl([MarshalAs(UnmanagedType.LPWStr)] string pcszUrl, int dwInFlags); void GetUrl([MarshalAs(UnmanagedType.LPWStr)] out StringBuilder ppszUrl); void InvokeCommand(IntPtr purlici); } [ComImport] [Guid("FBF23B40-E3F0-101B-8488-00AA003E56F8")] public class InternetShortcut { } The following works as expected: var ishort = new InternetShortcut(); ((IPersistFile)ishort).Load("MyLink.url", 0); ((IUniformResourceLocatorW)ishort).GetUrl(out url); However: If I comment out IUniformResourceLocatorW.SetUrl (which I am not using), IUniformResourceLocatorW.GetUrl throws a COMException (HResult 0x80041001). If I switch between IUniformResourceLocatorW.SetUrl and IUniformResourceLocatorW.GetUrl (that is place the former below the latter) the same exception is thrown If I comment out IUniformResourceLocatorW.InvokeCommand the code runs fine. It's as if the order has to be preserved "up to" the invoked method. Is this behavior by design? documented somewhere? I'm asking because some COM interfaces are composed of many methods with possibly many supporting types and I'd rather avoid defining what I don't need if possible.

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