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• Cannot create a new VS data connection in Server Explorer

  - by Seventh Element

  I have a local instance of SQL Server 2008 express edition running on my development PC. I'm trying to create a new data connection through Visual Studio Server Explorer. The steps are the following: Right click the "Data Connections" node = Choose Data Source. I select "Microsoft SQL Server" as the data source. The "Add Connection" dialog window appears. I select my local server instance = "Test connection" works fine. I select "AdventureWorks" as the database name = "Test connection" works fine. Next I hit the "Ok" button = Error message: "This server version is not supported. Only servers up to MS SQL Server 2005 are supported." I'm using Visual Studio 2008 Professional Edition. The target framework of the application is ".NET framework 3.5". I have a reference to System.Data (framework v2.0) and cannot find another version of the assembly on my system. Am I referencing the wrong assembly? How can I fix this problem?

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• Need help/suggestions for creating fantasy sports scoring databases and queries

  - by MGumbel

  I'm trying to create a website for my friends and I to keep track of fantasy sports scoring. So far, I've been doing the calculations and storage in Excel, which is very tedious. I'm trying to make it more simplified and automated through a SQL database that I can then wrap a web app around to enter daily stat updates. It's premised on our participation in another commercial site where we trade virtual shares of athletes, and thus acquire an "ownership percentage" in each athlete. For instance, if there are 100 shares of AROD, and I own 10 shares, then I own 10%. It then applies this to traditional baseball rotisserie scoring. So, for instance, if AROD has 1 HR today, then his adjusted HR stat would be 1.10. If he also has 2 RBI's, then his adjusted RBI stat today would be 2.20, based on (2 x 1.10)(1 to normalize the stat, and the .10 to represent the ownership percentage). All the stats for my team would then be summed each day and added to my stat history to come to an aggregated total. After that, points are allocated based on the ranking of each participant in each category at the end of the day. E.g. if there are 10 participants, and I have the highest total aggregate number of Adjusted HR's, then I get 10 pts. The points are then summed across the different stat categories to come up with a total point ranking for that day. An added difficulty is that ownership %'s can change on a daily basis. So far, in playing around with different schema, I don't know that having a separate table for each athlete's stats and each player's ownership %'s is the wisest choice. It seems to me that simply having two tables, one that contains the daily stat information for each athlete, and another that shows the ownership % of each player. My friend suggested using a start and end date for each ownership % to represent the potential daily changes in this category. I'm admittedly new to database development, so any suggestions on query code would be appreciated.

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• Can anyone help why my mockery doesn't work?

  - by user509550

  The test call real method(service) without mocking some expecations @Test public void testPropertyList() { Credentials creds = new Credentials(); creds.setUsername("someEmail"); creds.setPassword("somePassword"); creds.setReferrer("someReferrer"); final Collection<PropertyInfo> propertyInfoCollection = new LinkedList<PropertyInfo>(); final List<ListingInfo> listings = new ArrayList<ListingInfo>(); listings.add(listingInfoMock); listings.add(listingInfoMock); propertyInfoCollection.add(new PropertyInfo("c521bf5796274bd587c00bec80583c00", listings)); MultivaluedMap<String, String> params = new MultivaluedMapImpl(); params.add("page", "5"); params.add("size", "5"); instance.setPropertyListFacade(propertyListFacadeMock); mockery.checking(new Expectations() { { one(propertyListFacadeMock).getUserProperties(); will(returnValue(propertyInfoCollection)); one(listingInfoMock).getPropertyName(); allowing(listingInfoMock).getThumbnailURL(); one(listingInfoMock).getListingSystemId(); one(listingInfoMock).getPropertyURL(); one(listingInfoMock).getListingSystemId(); one(listingInfoMock).getPropertyURL(); } }); instance.setSessionManager(dashboardSessionManagerMock); testSuccessfulAuthenticate(); ClientResponse response = resource.path(PROPERTIES_PATH).queryParams(params).accept(MediaType.APPLICATION_XML) .get(ClientResponse.class); assertEquals(200, response.getStatus()); mockery.assertIsSatisfied(); }

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• Javascript, IE, Strings, and Performance problems

  - by Infinity

  Hey guys, So we have this product, and it's really slow in IE. We've already applied a lot of the practices advised by the IE guys themselves (like this, and this), and try to sacrifice clean code for performance in the critical parts like DOM manipulation. However, as you can see in this IE profiler screenshot.. Just "String" is the biggest offender. Almost 750ms of exclusive time. Does this mean IE is spending 750ms just instantiating Strings? I also read this stuff on the Opera dev blog: A build script can remove whitespace, comments, replace strings with Array lookups (to avoid MSIE creating a string object for every single instance of a string — even in conditions) But no more info regarding this. Anyone can clarify? It seems like IE has to create a full String instance every time you have " " in your code, which could explain this, but I don't know what the array lookup optimization would look like. BTW- we don't really do much of string concatenation anywhere in the code. The library we use is MooTools 1.2.4 Any suggestions will be appreciated! Thx

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• tcp/ip accept not returning, but client does

  - by paquetp

  server: vxworks 6.3 calls the usual socket, bind, listen, then: for (;;) { client = accept(sfd,NULL,NULL); // pass client to worker thread } client: .NET 2.0 TcpClient constructor to connect to server that takes the string hostname and int port, like: TcpClient client = new TcpClient(server_ip, port); This is working fine when the server is compiled and executed in windows (native c++). intermittently, the constructor to TcpClient will return the instance, without throwing any exception, but the accept call in vxWorks does not return with the client fd. tcpstatShow indicates no accept occurred. What could possibly make the TcpClient constructor (which calls 'Connect') return the instance, while the accept call on the server not return? It seems to be related to what the system is doing in the background - it seems more likely to get this symptom to occur when the server is busy persisting data to flash or an NFS share when the client attempts to connect, but can happen when it isn't also. I've tried adjusting priority of the thread running accept I've looked at the size of the queue in 'listen'. There's enough. The total number of file descriptors available should be enough (haven't validated this yet though, first thing in the morning)

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• How to "wrap" implementation in C#

  - by igor

  Hello, I have these classes in C# (.NET Framework 3.5) described below: public class Base { public int State {get; set;} public virtual int Method1(){} public virtual string Method2(){} ... public virtual void Method10(){} } public class B: Base { // some implementation } public class Proxy: Base { private B _b; public class Proxy(B b) { _b = b; } public override int Method1() { if (State == Running) return _b.Method1(); else return base.Method1(); } public override string Method2() { if (State == Running) return _b.Method2(); else return base.Method2(); } public override void Method10() { if (State == Running) _b.Method10(); else base.Method10(); } } I want to get something this: public Base GetStateDependentImplementation() { if (State == Running) // may be some other rule return _b; else return base; // compile error } and my Proxy's implementation will be: public class Proxy: Base { ... public override int Method1() { return GetStateDependentImplementation().Method1(); } public override string Method2() { return GetStateDependentImplementation().Method2(); } ... } Of course, I can do this (aggregation of base implementation): public RepeaterOfBase: Base // no any overrides, just inheritance { } public class Proxy: Base { private B _b; private RepeaterOfBase _Base; public class Proxy(B b, RepeaterOfBase aBase) { _b = b; _base = aBase; } } ... public Base GetStateDependentImplementation() { if (State == Running) return _b; else return _Base; } ... But instance of Base class is very huge and I have to avoid to have other additional copy in memory. So I have to simplify my code have to "wrap" implementation have to avoid a code duplication have to avoid aggregation of any additional instance of Base class (duplication) Is it possible to reach these goals?

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• Implementing Unowned relationship Google App Engine

  - by nwallman

  My question is more of a best practices question on how to implement unowned relationships with Google App Engine. I am using JDO to do my persistence and like recommended in the google docs I'm persisting my list of unowned relationships like so: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class User implements Serializable, UserDetails { ... @Persistent private List<Key> groups; ... } Now I came across my predicament when I went to query that list of objects using they Key object. So when I get my list of group keys in order to actually return a list of Group objects I have to do a look up on that key to get the object. My question is what is the recommended way of doing a unowned look up on a model object? Should I have an instance of the PersistanceManagerFactory on my Model object so I can do a lookup? Should I have an instance of my GroupDAO object on my Model object so I can do a look up? Should I have a Utility to do this type of lookup? I'm new to this so I just want to know which is the best way to do this. Thanks.

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• Exception when click DataGridview tab c#, .Net 4.0

  - by Nguyen Nam

  My winform app have two tab and multi thread, one is main tab and other is log tab. I only use log tab to show logs in a datagridview control. Exception is random occurred when click to log tab (Not click to row or colunm), i have try but can not find anyway to fix it. This is the error log: Message : Object reference not set to an instance of an object. Source : System.Windows.Forms TargetSite : System.Windows.Forms.DataGridViewElementStates GetRowState(Int32) StackTrace : at System.Windows.Forms.DataGridViewRowCollection.GetRowState(Int32 rowIndex) at System.Windows.Forms.DataGridView.ComputeHeightOfFittingTrailingScrollingRows(Int32 totalVisibleFrozenHeight) at System.Windows.Forms.DataGridView.GetOutOfBoundCorrectedHitTestInfo(HitTestInfo& hti, Int32& mouseX, Int32& mouseY, Int32& xOffset, Int32& yOffset) at System.Windows.Forms.DataGridView.OnMouseMove(MouseEventArgs e) at System.Windows.Forms.Control.WmMouseMove(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.DataGridView.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) Message : Object reference not set to an instance of an object. Source : System.Windows.Forms TargetSite : Void ClearInternal(Boolean) StackTrace : at System.Windows.Forms.DataGridViewRowCollection.ClearInternal(Boolean recreateNewRow) at System.Windows.Forms.DataGridView.OnClearingColumns() at System.Windows.Forms.DataGridViewColumnCollection.Clear() at System.Windows.Forms.DataGridView.Dispose(Boolean disposing) at System.ComponentModel.Component.Dispose() at System.Windows.Forms.Control.Dispose(Boolean disposing) at System.ComponentModel.Component.Dispose() at System.Windows.Forms.Control.Dispose(Boolean disposing) at System.Windows.Forms.TabControl.Dispose(Boolean disposing) at System.ComponentModel.Component.Dispose() at System.Windows.Forms.Control.Dispose(Boolean disposing) at System.Windows.Forms.Form.Dispose(Boolean disposing) Update status code: private void updateMessage(int index, string message) { try { this.dgForums.Rows[index].Cells["ColStatus"].Value = message; System.Windows.Forms.Application.DoEvents(); } catch { } }

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• JAR files, don't they just bloat and slow Java down?

  - by Josamoto

  Okay, the question might seem dumb, but I'm asking it anyways. After struggling for hours to get a Spring + BlazeDS project up and running, I discovered that I was having problems with my project as a result of not including the right dependencies for Spring etc. There were .jars missing from my WEB-INF/lib folder, yes, silly me. After a while, I managed to get all the .jar files where they belong, and it comes at a whopping 12.5MB at that, and there's more than 30 of them! Which concerns me, but it probably and hopefully shouldn't be concerned. How does Java operate in terms of these JAR files, they do take up quite a bit of hard drive space, taking into account that it's compressed and compiled source code. So that can really quickly populate a lot of RAM and in an instant. My questions are: Does Java load an entire .jar file into memory when say for instance a class in that .jar is instantiated? What about stuff that's in the .jar that never gets used. Do .jars get cached somehow, for optimized application performance? When a single .jar is loaded, I understand that the thing sits in memory and is available across multiple HTTP requests (i.e. for the lifetime of the server instance running), unlike PHP where objects are created on the fly with each request, is this assumption correct? When using Spring, I'm thinking, I had to include all those fiddly .jars, wouldn't I just be better off just using native Java, with say at least and ORM solution like Hibernate? So far, Spring just took extra time configuring, extra hard drive space, extra memory, cpu consumption, so I'm concerned that the framework is going to cost too much application performance just to get for example, IoC implemented with my BlazeDS server. There still has to come ORM, a unit testing framework and bits and pieces here and there. It's just so easy to bloat up a project quickly and irresponsibly easily. Where do I draw the line?

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• How can I avoid encoding mixups of strings in a C/C++ API?

  - by Frerich Raabe

  I'm working on implementing different APIs in C and C++ and wondered what techniques are available for avoiding that clients get the encoding wrong when receiving strings from the framework or passing them back. For instance, imagine a simple plugin API in C++ which customers can implement to influence translations. It might feature a function like this: const char *getTranslatedWord( const char *englishWord ); Now, let's say that I'd like to enforce that all strings are passed as UTF-8. Of course I'd document this requirement, but I'd like the compiler to enforce the right encoding, maybe by using dedicated types. For instance, something like this: class Word { public: static Word fromUtf8( const char *data ) { return Word( data ); } const char *toUtf8() { return m_data; } private: Word( const char *data ) : m_data( data ) { } const char *m_data; }; I could now use this specialized type in the API: Word getTranslatedWord( const Word &englishWord ); Unfortunately, it's easy to make this very inefficient. The Word class lacks proper copy constructors, assignment operators etc.. and I'd like to avoid unnecessary copying of data as much as possible. Also, I see the danger that Word gets extended with more and more utility functions (like length or fromLatin1 or substr etc.) and I'd rather not write Yet Another String Class. I just want a little container which avoids accidental encoding mixups. I wonder whether anybody else has some experience with this and can share some useful techniques. EDIT: In my particular case, the API is used on Windows and Linux using MSVC 6 - MSVC 10 on Windows and gcc 3 & 4 on Linux.

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• How can I handle arbitrary text as "nouns" in Inform 7?

  - by Beska

  In Inform, I'd like to be able to create a new action, and have it be able to work on aribitrary text. I can easily create a new action that will work on existing things. Finding is an action with past participle found, applying to one thing. Understand "Find [something]" as finding. Carry out finding: say "You find [the noun]." But this only works on items that exist within the game world. If I try to "find fdsljk", for instance, it will fail because I haven't created a "fdsljk". I'd like to be able to "find fdsljk" and then be able to grab that extra text and respond with it...something like "You find the fdsljk." I was thinking that something like A foo is a kind of value. Finding is an action with past participle found, applying to one foo. Understand "Find [something]" as finding. Carry out finding: say "You find [the foo]." might be close...but it doesn't work. I get an error that reads: You wrote 'say "You find [the foo]."' , and in particular 'the foo': but this asked to say something of a kind which can't be said, or rather, printed. Although this problem can arise when you use complicated text substitutions which come in variant forms depending on the kinds of value used, far more often what this means is just that you tried to use a substituted value (e.g., in 'say "The dial reads [V]."') of a kind which could not be printed out. For instance, if V is a number or a piece of text, there is no problem: but if V is a parsing topic, say an entry in a 'topic' column of a table, then this problem will arise. The italics are mine, and highlight the key...I think this should be doable, but I'm taking the wrong path. Clues?

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• Magic Method __set() on a Instantiated Object

  - by streetparade

  Ok i have a problem, sorry if i cant explaint it clear but the code speaks for its self. i have a class which generates objects from a given class name; Say we say the class is Modules: public function name($name) { $this->includeModule($name); try { $module = new ReflectionClass($name); $instance = $module->isInstantiable() ? $module->newInstance() : "Err"; $this->addDelegate($instance); } catch(Exception $e) { Modules::Name("Logger")->log($e->getMessage()); } return $this; } The AddDelegate Method: protected function addDelegate($delegate) { $this->aDelegates[] = $delegate; } The __call Method public function __call($methodName, $parameters) { $delegated = false; foreach ($this->aDelegates as $delegate) { if(class_exists(get_class($delegate))) { if(method_exists($delegate,$methodName)) { $method = new ReflectionMethod(get_class($delegate), $methodName); $function = array($delegate, $methodName); return call_user_func_array($function, $parameters); } } } The __get Method public function __get($property) { foreach($this->aDelegates as $delegate) { if ($delegate->$property !== false) { return $delegate->$property; } } } All this works fine expect the function __set public function __set($property,$value) { //print_r($this->aDelegates); foreach($this->aDelegates as $k=>$delegate) { //print_r($k); //print_r($delegate); if (property_exists($delegate, $property)) { $delegate->$property = $value; } } //$this->addDelegate($delegate); print_r($this->aDelegates); } class tester { public function __set($name,$value) { self::$module->name(self::$name)->__set($name,$value); } } Module::test("logger")->log("test"); // this logs, it works echo Module::test("logger")->path; //prints /home/bla/test/ this is also correct But i cant set any value to class log like this Module::tester("logger")->path ="/home/bla/test/log/"; The path property of class logger is public so its not a problem of protected or private property access. How can i solve this issue? I hope i could explain my problem clear.

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• JavaScript functions broke my page jumps?

  - by Mark

  Hi everybody, I'm trying to develop a personal website and running into some issues. At the top of my page I had a horizontal table that contained 6 different images (buttons) that linked to different sections of the page. I wanted to spice up the buttons with JavaScript and make the image of the button change onMouseOver and onMouseOut so I found a way to do so online with some JavaScript but the problem now is that the buttons no longer jump to the appropriate section of the page when using Google Chrome or Safari, but in IE 9 they still do work correctly... Here is my old code that worked properly: <html> ... <body> <center> <table border="1" style="color:#D80000;text-align:center"> <tr> <td> <a href="#about"><img src="images/aboutMe.png" alt="About Me"></a> </td> <td> <a href="#courses"><img src="images/courseList.png" alt="Courses"></a> </td> <td> <a href="#work"><img src="images/workHistory.png" alt="Work History"></a> </td> <td> <a href="#places"><img src="images/placesBeen.png" alt="Places I've Been"></a> </td> <td> <a href="#games"><img src="images/gamesPlay.png" alt="Games I Play"></a> </td> <td> <a href="#contact"><img src="images/contactMe.png" alt="Contact"></a> </td> </tr> </table> </center> ... </body> </html> Here is my new code that is now broken: <html> <head> ... <script type="text/javascript"> <!-- if (document.images) { <!-- Preload original Images --> var about_init= new Image(); about_init.src="images/aboutMe.png"; var courses_init= new Image(); courses_init.src="images/courseList.png"; var work_init= new Image(); work_init.src="images/workHistory.png"; var places_init= new Image(); places_init.src="images/placesBeen.png"; var games_init= new Image(); games_init.src="images/gamesPlay.png"; var contact_init= new Image(); contact_init.src="images/contactMe.png"; <!--Preload images for mouseover --> var about_new= new Image(); about_new.src="images/aboutAlt.png"; var courses_new= new Image(); courses_new.src="images/courseAlt.png"; var work_new= new Image(); work_new.src="images/workAlt.png"; var places_new= new Image(); places_new.src="images/placesAlt.png"; var games_new= new Image(); games_new.src="images/gamesAlt.png"; var contact_new= new Image(); contact_new.src="images/contactAlt.png"; } function change_it(the_name) { if (document.images) { document.images[the_name].src= eval(the_name+"_new.src"); } } function change_back(the_name) { if (document.images) { document.images[the_name].src= eval(the_name+"_init.src"); } } //--> </script> </head> <body> ... <center> <table border="1" style="color:#D80000;text-align:center"> <tr> <td> <a href="#about" onMouseOver="change_it('about')" onMouseOut="change_back('about')"><img src="images/aboutMe.png" name="about" id="about" border="0" alt="About Me"></a> </td> <td> <a href="#courses" onMouseOver="change_it('courses')" onMouseOut="change_back('courses')"><img src="images/courseList.png" name="courses" id="courses" border="0" alt="Courses"></a> </td> <td> <a href="#work" onMouseOver="change_it('work')" onMouseOut="change_back('work')"><img src="images/workHistory.png" name="work" id="work" border="0" alt="Work History"></a> </td> <td> <a href="#places" onMouseOver="change_it('places')" onMouseOut="change_back('places')"><img src="images/placesBeen.png" name="places" id="places" border="0" alt="Places I've Been"></a> </td> <td> <a href="#games" onMouseOver="change_it('games')" onMouseOut="change_back('games')"><img src="images/gamesPlay.png" name="games" id="games" border="0" alt="Games I Play"></a> </td> <td> <a href="#contact" onMouseOver="change_it('contact')" onMouseOut="change_back('contact')"><img src="images/contactMe.png" name="contact" id="contact" border="0" alt="Contact"></a> </td> </tr> </table> </center> ... </body> </html> The images properly switch when the mouse is moved over/off them, but the jump to the corresponding page sections seems to be broken, it seems like they're all jumping to the #about section now. Once again, the weirder thing is that this is only the case when I'm using Google Chrome on my laptop running Windows 7 or Safari using my iPhone 4 but when I use the new Internet Explorer 9 on my laptop running Windows 7 all the buttons still link correctly. Any idea what's breaking the links?

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• Easy ways to investigate unknown Python APIs

  - by jedi_coder

  When studying a snippet of unknown Python code, I occasionally bump into the varName.methodName() pattern. To figure out what's this, I shall study the code more, find where varName was instantiated, find its type. So if varName proves to be an instance of ClassName class, I would knew that methodName() is a method of ClassName. Sometimes varName == self and methodName() is a method of this class, or a method inherited from some other class, if the current class is subclassing some other classes. Are there quick ways / tools that could take 'methodName' as input, scan over all installed Python modules and show which classes have methodName()? The closest thing related to this I know of is ipython. If I type a class name, then dot ('.') then TAB, it can show the class members. Instead of a class I could use a name of an object (which is an instance of a certain class) and it would work too. As soon as I choose a method name from the provided options, I can type '?' or '??' and get some help if there's a docstring. I wonder if ipython can do some intelligent scanning based only on 'methodName' string. If you know alternatives to ipython that could possibly help with this, please do suggest them.

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• Calling a WPF Appliaction and modify exposed properties?

  - by Justin

  I have a WPF Keyboard Application, it is developed in such a way that an application could call it and modify its properties to adapt the Keyboard to do what it needs to. Right now I have a file *.Keys.Set which tells the appliaction (on open) to style itself according to that new style. I know this file could be passed as a command line argument into the appliaction. That would not be a problem. My concern is, is thier a way via a managed environment to change the properties of the executable as long as they are exposed properly, an example: 'Creates a new instance of the Keyboard Appliaction Dim e_key as new WpfAppliaction("C:\egt\components\keyboard.exe") 'Sets the style path e_key.SetStylePath("c:\users\joe\apps\me\default.keys.set") e_key.Refresh() 'Applies the style e_key.HideMenu() 'Hides the menu e_key.ShowDeck("PIN") 'Shows the custom "deck" of keyboard keys the developer 'Created in the style appliaction. ''work with events and resposne 'Clear the instance from memory e_key.close e_key.dispose e_key = nothing This would allow my application to become easily accessible to other Touch Screen Application Developers, allowing them to use my key_board and keep the functionality they need. It seems like it might be possible because (name of executable).application shows all the exposed functions, properties, and values. I just have never done this before. Any help would be appreciated, thank you in advance.

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• django multiprocess problem

  - by iKiR

  I have django application, running under lighttpd via fastcgi. FCGI running script looks like: python manage.py runfcgi socket=<path>/main.socket method=prefork \ pidfile=<path>/server.pid \ minspare=5 maxspare=10 maxchildren=10 maxrequests=500 \ I use SQLite. So I have 10 proccess, which all work with the same DB. Next I have 2 views: def view1(request) ... obj = MyModel.objects.get_or_create(id=1) obj.param1 = <some value> obj.save () def view2(request) ... obj = MyModel.objects.get_or_create(id=1) obj.param2 = <some value> obj.save () And If this views are executed in two different threads sometimes I get MyModel instance in DB with id=1 and updated either param1 or param2 (BUT not both) - it depends on which process was the first. (of course in real life id changes, but sometimes 2 processes execute these two views with same id) The question is: What should I do to get instance with updated param1 and param2? I need something for merging changes in different processes. One decision is create interprocess lock object but in this case I will get sequence executing views and they will not be able to be executed simultaneously, so I ask help

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• How do I avoid a race condition in my Rails app?

  - by Cathal

  Hi, I have a really simple Rails application that allows users to register their attendance on a set of courses. The ActiveRecord models are as follows: class Course < ActiveRecord::Base has_many :scheduled_runs ... end class ScheduledRun < ActiveRecord::Base belongs_to :course has_many :attendances has_many :attendees, :through => :attendances ... end class Attendance < ActiveRecord::Base belongs_to :user belongs_to :scheduled_run, :counter_cache => true ... end class User < ActiveRecord::Base has_many :attendances has_many :registered_courses, :through => :attendances, :source => :scheduled_run end A ScheduledRun instance has a finite number of places available, and once the limit is reached, no more attendances can be accepted. def full? attendances_count == capacity end attendances_count is a counter cache column holding the number of attendance associations created for a particular ScheduledRun record. My problem is that I don't fully know the correct way to ensure that a race condition doesn't occur when 1 or more people attempt to register for the last available place on a course at the same time. My Attendance controller looks like this: class AttendancesController < ApplicationController before_filter :load_scheduled_run before_filter :load_user, :only => :create def new @user = User.new end def create unless @user.valid? render :action => 'new' end @attendance = @user.attendances.build(:scheduled_run_id => params[:scheduled_run_id]) if @attendance.save flash[:notice] = "Successfully created attendance." redirect_to root_url else render :action => 'new' end end protected def load_scheduled_run @run = ScheduledRun.find(params[:scheduled_run_id]) end def load_user @user = User.create_new_or_load_existing(params[:user]) end end As you can see, it doesn't take into account where the ScheduledRun instance has already reached capacity. Any help on this would be greatly appreciated.

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• How do I differentiate between different descendents with the same name?

  - by zotty

  I've got some XML I'm trying to import with c#, which looks something like this: <run> <name = "bob"/> <date = "1958"/> </run> <run> <name = "alice"/> <date = "1969"/> </run> I load my xml using XElement xDoc=XElement.Load(filename); What I want to do is have a class for "run", under which I can store names and dates: public class RunDetails { public RunDetails(XElement xDoc, XNamespace xmlns) { var query = from c in xDoc.Descendants(xmlns + "run").Descendants(xmlns + "name") select c; int i=0; foreach (XElement a in query) { this.name= new NameStr(a, xmlns); // a class for names Name.Add(this.name); //Name is a List<NameStr> i++; } // Here, i=2, but what I want is a new instance of the RunDetails class for each <run> } } How can I set up my code to create a new instance of the RunDetails class for every < run, and to only select the < name and < date inside a given < run?

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• "Abstract static" method - how?

  - by polyglot

  There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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• dynamic inheritance without touching classes

  - by Jasper

  I feel like the answer to this question is really simple, but I really am having trouble finding it. So here goes: Suppose you have the following classes: class Base; class Child : public Base; class Displayer { public: Displayer(Base* element); Displayer(Child* element); } Additionally, I have a Base* object which might point to either an instance of the class Base or an instance of the class Child. Now I want to create a Displayer based on the element pointed to by object, however, I want to pick the right version of the constructor. As I currently have it, this would accomplish just that (I am being a bit fuzzy with my C++ here, but I think this the clearest way) object->createDisplayer(); virtual void Base::createDisplayer() { new Displayer(this); } virtual void Child::createDisplayer() { new Displayer(this); } This works, however, there is a problem with this: Base and Child are part of the application system, while Displayer is part of the GUI system. I want to build the GUI system independently of the Application system, so that it is easy to replace the GUI. This means that Base and Child should not know about Displayer. However, I do not know how I can achieve this without letting the Application classes know about the GUI. Am I missing something very obvious or am I trying something that is not possible?

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• Comparing objects and inheritance

  - by ereOn

  Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

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• CodeModel help needed for right-hand singleton.getinstance() assignment.

  - by antarti

  I've been able to generate 99% of what I need with the CodeModel API, but I am stumped here... Using the various "directXX" methods does not add import statements to the generated code, and I can work without the "directXXX" type of methods except for one place in a generated class. Suppose I desire a generated method like: /** * Copies data from this Value-Obj instance, to the returned PERSON instance. * * @return PERSON * */ public PERSON mapVOToPERSON() throws MappingException { Mapper mapper = (com.blah.util.MapperSingleton.getMapperInstance()); return mapper.map(this, PERSON.class); } You can see the right hand of the Mapper assignment in parens. Emitting the entire package+class was the only way I could find to just declare "SomeSingleton.someMethod()" on the right hand side and have the generated code compile. Without the MapperSingleton being added to the object model, there is no import generated... Questions: 1) Is there a way to force an import to be generated? 2) How to declare an expression that gives me the right side of the Mapper assignment within the object model (so that an import of MapperSingleton gets generated. Any help appreciated...

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• Handling very large lists of objects without paging?

  - by user246114

  Hi, I have a class which can contain many small elements in a list. Looks like: public class Farm { private ArrayList<Horse> mHorses; } just wondering what will happen if the mHorses array grew to something crazy like 15,000 elements. I'm assuming that trying to write and read this from the datastore would be crazy, because I'd get killed on the serialization process. It's important that I can get the entire array in one shot without paging, and each Horse element may only have two string properties in it, so they are pretty lightweight: public class Horse { private String mId; private String mName; } I don't need these horses indexed at all. Does it sound reasonable to just store the mHorse array as a raw Text field, and force my clients to do the deserialization? Something like: public class Farm { private Text mHorsesSerialized; } then whenever the client receives a Farm instance, it has to take the raw string of horses, and split it in order to reinstantiate the list, something like: // GWT client perhaps Farm farm = rpcCall.getMyFarm(); String horsesSerialized = farm.getHorses(); String[] horseBlocks = horsesSerialized.split(","); for (int i = 0; i < horseBlocks.length; i++) { // .. continue deserializing the individual objects ... } yeah... so hopefully it would be quick to read a Farm instance from the datastore, and the serialization penalty is paid by the client, Thanks

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• Why would one want to use the public constructors on Boolean and similar immutable classes?

  - by Robert J. Walker

  (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

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• How do you update a secondary view?

  - by Troy Sartain

  Perhaps there's a better way to set this up so I'm open to suggestions. But here's what I'm doing. I have a main UIView. On top of that I have a UIImageView and another UIView. When the UIImageView changes, I want to change the second UIView. So I have a class for it and the IB object's type is set to the class. In the .m of that class is a drawRect method that draws some rectangles. Also in the .m is a NSMutableArray property that is synthesized. I created an instance of that class in the controller of the main view. The problem: despite the fact that the drawRect works fine when the app starts (as traced in the debugger,) when the UIImageView changes I call a "setNeedsDisplay" on the instance variable of the second view after updating the @synthesize'd array but the drawRect does not get called. I think it has to do with instances. I wouldn't think threading would be an issue here. I just want to draw in a separate area of the screen based on an image also displayed.

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