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  • How can I get this code involving unique_ptr and emplace_back to compile?

    - by Neil G
    #include <vector> #include <memory> using namespace std; class A { public: A(): i(new int) {} A(A const& a) = delete; A(A &&a): i(move(a.i)) {} unique_ptr<int> i; }; class AGroup { public: void AddA(A &&a) { a_.emplace_back(move(a)); } vector<A> a_; }; int main() { AGroup ag; ag.AddA(A()); return 0; } does not compile... (says that unique_ptr's copy constructor is deleted) I tried replacing move with forward. Not sure if I did it right, but it didn't work for me.

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  • Python lazy property decorator

    - by detly
    Recently I've gone through an existing code base and refactored a lot of instance attributes to be lazy, ie. not be initialised in the constructor but only upon first read. These attributes do not change over the lifetime of the instance, but they're a real bottleneck to calculate that first time and only really accessed for special cases. I find myself typing the following snippet of code over and over again for various attributes across various classes: class testA(object): def __init__(self): self._a = None self._b = None @property def a(self): if self._a is None: # Calculate the attribute now self._a = 7 return self._a @property def b(self): #etc Is there an existing decorator to do this already in Python that I'm simply unaware of? Or, is there a reasonably simple way to define a decorator that does this? I'm working under Python 2.5, but 2.6 answers might still be interesting if they are significantly different.

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  • adding tabs to tabcontrol from inside usercontrol

    - by Jakob
    How can I add tabs to a tabcontrol that exists in one usercontrol from another usercontrol that is contained within a tab itself?? Can I do it without passing in the tabcontrol as a parameter in the constructor, perhaps via some static global method? I've tried public static ObservableTabCollection FindCollectionFromUC(this DependencyObject depObject) { bool loop = true; var parent = (VisualTreeHelper.GetParent(depObject) as FrameworkElement); while (loop) { if (parent.GetType() is TabControl) { loop = false; return ((ObservableTabCollection)((TabControl)parent).ItemsSource); } } return null; } but this is just an infinite loop

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  • UserControl Behaviour on a Windows Form

    - by AK
    Hi, I have a usercontrol UC1 with a combobox and a button. From the constructor, after initializing all the controls, I am populating the combobox with an array of information brought from other class library. I have kept the UC1 on windows form. When I tried to open the form's designer I see some errors and a suggestion to rebuild to fix the errors. After searching over net I found that the logic of populating the combobox is the culprit. I changed the code with an additional check of null and the issue is fixed now. My question is, how am i able to see the same usercontrol seperatly in designer view, but not when i placed the UC1 on a form and trying to see the designer view for the form? The same combobox populating logic should affect the drawing of UC1 when I try to see it in designer view right? Thanks, AK.

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  • as3 swc component preview through code

    - by David
    I am developing an as3 swc-based component that populates its contents entirely through actionscript in the constructor (e.g. sprite.graphics.lineTo...). When I drag the component onto the stage, it is empty. If I export my movie, everything works perfectly, but I also need the live preview to work. I could get around this with a placeholder graphic, but I would much rather leave it purely as code. Is there any way to get around this? Thanks, David.

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  • Clear all class variables between instances

    - by ensnare
    This is probably a stupid question, but what's the best way to clear class variables between instances? I know I could reset each variable individually in the constructor; but is there a way to do this in bulk? Or am I doing something totally wrong that requires a different approach? Thanks for helping ... class User(): def __init__(self): #RESET ALL CLASS VARIABLES def commit(self): #Commit variables to database >>u = User() >>u.name = 'Jason' >>u.email = '[email protected]' >>u.commit() So that each time User is called the variables are fresh. Thanks.

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  • Why is there an implicit conversion from Float/Double to BigDecimal, but not from String?

    - by soc
    Although the situation of conversion from Doubles to BigDecimals has improved a bit compared to Java scala> new java.math.BigDecimal(0.2) res0: java.math.BigDecimal = 0.20000000000000001110223024625156... scala> BigDecimal(0.2) res1: scala.math.BigDecimal = 0.2 and things like val numbers: List[BigDecimal] = List(1.2, 3.2, 0.7, 0.8, 1.1) work really well, wouldn't it be reasonable to have an implicit conversion like implicit def String2BigDecimal(s: String) = BigDecimal(s) available by default which can convert Strings to BigDecimals like this? val numbers: List[BigDecimal] = List("1.2", "3.2", "0.7", "0.8", "1.1") Or am I missing something and Scala resolved all "problems" of Java with using the BigDecimal constructor with a floating point value instead of a String, and BigDecimal(String) is basically not needed anymore in Scala?

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  • NHibernate custom connection string configuration

    - by user177883
    I have a c# library project, that i configured using nhibernate, and I like people to be able to import this project and use the project. This project has FrontController that does all the work. I have a connection string in hibernate config file and in app.config file of another project. it would be nice for anyone to be able to set the connection string into this library project and use it. such as through a method which will take the connectiong string as parameter. or when creating a new instance of FrontController to pass the connection string to constructor. or if you have a better idea. How to do this? I d like this class library to use the same database of the project that s imported. How to set hibernate connection string programatically? same idea for log4net.

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  • F# Silverlight 3.0 Custom Control Property throws: NullReferenceException

    - by akaphenom
    A new issue since my previous post. I am having some issues with the properties of the control in my Control Class I havse defined: static member ItemsProperty : DependencyProperty = DependencyProperty.Register( "Items", typeof<MyMenuItemCollection>, typeof<MyMenu>, null); member this.Items with get () : MyMenuItemCollection = this.GetValue(MyMenu.ItemsProperty) :?> MyMenuItemCollection and set (value: MyMenuItemCollection) = this.SetValue(MyMenu.ItemsProperty, value); The problem occurs on access: for menuItem in this.Items do let contentElement: FrameworkElement = menuItem.Content where I get a null referce exception on this.Items; 'Items' threw an exception of type 'System.NullReferenceException' Immediately after I initialized in the constructor: do this.Items <- new CoolMenuItemCollection()

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  • trouble configuring WCF to use session

    - by Michael
    I am having trouble in configuring WCF service to run in session mode. As a test I wrote this simple service : [ServiceContract] public interface IService1 { [OperationContract] string AddData(int value); } [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerSession)] internal class Service1 : IService1,IDisposable { private int acc; public Service1() { acc = 0; } public string AddData(int value) { acc += value; return string.Format("Accumulator value: {0}", acc); } #region IDisposable Members public void Dispose() { } #endregion } I am using Net.TCP binding with default configuration with reliable session flag enabled. As far as I understand , such service should run with no problems in session mode. But , the service runs as in per call mode - each time I call AddData , constructor gets called before executing AddData and Dispose() is called after the call. Any ideas why this might be happening?

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  • Java : Storing Data in Array Of Object from JOptionPane Dialog

    - by Bader
    hi guys i need to know how i can insert data inside objects inside an array of objects using my already made Set methods. i need to know how should i do it through user , i mean JOptionPane input dialog [code] student[] s=new student[5]; for (int i=1 ; i <= s.length ;i++) { s[i] = new student(i,"AAA","Ecommerce",0.0); } for (int i=1; i<=s.length;i++) { name = JOptionPane.showInputDialog("Please Write Name for student n " + i); major = JOptionPane.showInputDialog("Please Write Major for student n " + i); gpa =Double.parseDouble(JOptionPane.showInputDialog("Please Write GPA for student n " +i)); s[i]=new student(i,name,major,gpa); } [/code] i tried to do vars here that get data from user by JOptionPane, but it seems that i only use my already made constructor , not the Set methods. i need to use the methods because it has some validation code inside it. any ideas ?

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  • Socksifying a Java ServerSocket - how to approach

    - by Thorbjørn Ravn Andersen
    I would like to have a Java program running on network A have a ServerSocket living on another network B through a proxy. I have played with a SOCKS5 proxy (which works) but it appears that all the proxy facilities in Java only work with client connections, not with ServerSockets (no constructor taking a Proxy argument). Asking Google gives much hay and few needles. What is the approach I should take to get this running? If a specific client is better than a generic SOCKS or web proxy then fine, but it needs to be Java (that leaves sshd out). Target JVM is preferrably Java 5, and then Java 6.

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  • PHP: How to cast object to inherited class?

    - by andreyvlru
    I'd like to inherit PDOStatement class and use it in my website scripts. But I am frustrated how to get required object. PDO::query returns only direct PDOStatement object and looks like there are no other method to create PDOStatement object or inherited class. Initially i thought to move PDOStatement object to constructor of inherit class Something like that: $stmt = PDO -> query("select * from messages"); $messageCollection = new Messaging_Collection($stmt); But how to make instance of PDOStatement to inherited object (Messaging_Collection). It is a big question for me. class Messaging_Collection extends PDOStatement { public function __construct(PDOStatement $stmt) { //there i should to transform $stmt to $this // direct $this = $stmt is not possible // is there other right way? }

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  • Background settings for a JDesktopPane

    - by EricR
    I'm using a self-made DesktopPaneUI for a JDesktopPane, I've written the proper methods for the class, and I'm running into trouble. When I resize the JDesktopPane, the background image doesn't resize with the frame. The image appears to be clipped at the size it was when the window initially opened. I'm giving it an image larger than the window, and I'm still having this problem. Here's my method call inside the constructor of my desktopUI class. super(); this.background = javax.imageio.ImageIO.read(new File(fileName)); Is there a way I can change my main class where I set the UI, or the myDesktopPaneUI class such that the background still fills the window when the JDesktopPane changes size? setUI(new myDesktopPaneUI("media/bg.jpg"));

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  • How do I invoke my custom settings provider?

    - by joebeazelman
    I need to specify a different location for my settings file. After many long hours of searching, I found out that I have to write my own SettingsProvider. I succeeded in creating one which allows me to specify a path for settings file via its constructor. Programatically, I can contruct it like this: var mycustomprovider = new CustomSettingsProvider(path); The problem I am having is that there's no way to invoke my custom provider. I can decorate the VS 2008 generated setting file with the following attribute: [SettingsProvider(typeof(CustomSettingProviders.CustomSettingsProvider))] internal sealed partial class Settings { } However, the attribute doesn't allow me to construct the object with a path. Also, I want to be able to set the SettingsProvider programmatically so that I can pass in any path I want at runtime and save my settings. The examples I've seen on the net have never mentioned how to use a invoke a SettingsProvider programmatically.

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  • How to use Dependency Injection with ASP.NET

    - by Schneider
    I am trying to work out a way to use Dependency Injection with ASP.NET controls. I have got lots of controls that create repositories directly, and use those to access and bind to data etc. I am looking for a pattern where I can pass repositories to the controls externally (IoC), so my controls remain unaware of how repositories are constructed and where they come from etc. I would prefer not to have a dependency on the IoC container from my controls, therefore I just want to be able to construct the controls with constructor or property injection. (And just to complicate things, these controls are being constructed and placed on the page by a CMS at runtime!) Any thoughts?

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  • AS3: Weak Listener References Not Appropriate During Initialization?

    - by TheDarkIn1978
    as i currently understand, if an event listener is added to an object with useWeakReference set to true, then it is eligible for garbage collection and will be removed if and when the garbage collection does a sweep. public function myCustomSpriteClass() //constructor { this.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownListener, false, 0, true); this.addEventListener(MouseEvent.MOUSE_UP, mouseUpListener, false, 0, true); } in this case, is it not appropriate to initialize an object with weak references event listeners, incase the garbage collector does activate a sweep removing the objects event listeners since they were added during initialization of the object? in this case, would it only be appropriate to create a type of deallocate() method which removes the event listeners before the object is nullified?

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  • myth about factory pattern

    - by leiz
    This has bothered me for awhile, and I have no clues if this is a myth. It seems that a factory pattern can ease the pain of adding a dependency for a class. For example, in a book, it has something like this Suppose that you have a class named Order. Initially it did not depend on anything. Therefore you didn't bother using a factory to create Order objects and you just used plain new to instantiate the objects. However, you now have a requirement that Order has to be created in association with a Customer. There are million places you need to change to add this extra parameter. If only you had de?ned a factory for the Order class, you would have met the new requirement without the same pain. How is this not same pain as adding an extra parameter to the constructor? I mean you would still need to provide an extra argument for the factory and that is also used by million places, right?

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  • C++ linking issue on Visual Studio 2008 when crosslinking different projects on same solution

    - by Luís Guilherme
    I'm using Google Test Framework to set some unit tests. I have got three projects in my solution: FN (my project) FN_test (my tests) gtest (Google Test Framework) I set FN_test to have FN and gtest as references (dependencies), and then I think I'm ready to set up my tests (I've already set everyone to /MTd (not doing this was leading me to linking errors before)). Particularly, I define a class called Embark in FN I would like to test using FN_test. So far, so good. Thus I write a classe called EmbarkTest using googletest, declare a member Embark* and write inside the constructor: EmbarkTest() { e = new Embark(900,2010); } Then , F7 pressed, I get the following: 1>FN_test.obj : error LNK2019: unresolved external symbol "public: __thiscall Embark::Embark(int,int)" (??0Embark@@QAE@HH@Z) referenced in function "protected: __thiscall EmbarkTest::EmbarkTest(void)" (??0EmbarkTest@@IAE@XZ) 1>D:\Users\lg\Product\code\FN\Debug\FN_test.exe : fatal error LNK1120: 1 unresolved externals Does someone know what have I done wrong and/or what can I do to settle this?

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  • Including non-standard C headers in C++

    - by Swaroop S
    I needed to include a few c headers ( non standard header files ) in my C++ code to be compiled by gcc. The C header (foo.h) has support for : #ifdef __cplusplus extern "C" { #endif and similarly at the end for }. The c++ code has the include "foo.h" I believe I should be able to just include the header (foo.h) and create instances of structs defined in the .h file. I am not able to compile the source code. It seems like the compiler looks at the c code as if it were c++ code. I see error such as error: expected constructor, destructor or type conversion before "(" Did I do something wrong ? I took advise from : http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html What else do i need to do, to tell the c++ compiler "expect and compile as c code" ?

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  • resource acquisition is initialization "RAII"

    - by hitech
    in the example below class X{ int *r; public: X(){cout<< X is created ; r new int[10]; } ~X(){cout<< X is destroyed ; delete [] r; } }; class Y { public: Y(){ X x; throw 44; } ~Y(){cout<< Y is destroyed ;} }; I got this example of RAII from one site and ave some doubts. please help. in the contructor of x we are not considering the scenation "if the memory allocation fails" . Here for the destructor of Y is safe as in y construcotr is not allocating any memory. what if we need to do some memory allocation also in y constructor?

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  • Java File and ByteArray or InputStream - please quick help

    - by Peter Perhác
    I want to use jFuge to play some MIDI music in an applet. There's a class for the MIDI pattern - Pattern - and the only method to load the pattern is from a File. Now, I don't know how applets load files and what not, but I am using a framework (PulpCore) that makes loading assets a simple task. If I need to grab an asset from a ZIP catalogue, I can use the Assets class which provides get() and getAsStream() methods. get() returns the given asset as a ByteArray, the other as an InputStream. I need jFuge to load the pattern from either ByteArray or InputStream. In pseudo-code, I would like to do this: Pattern.load(new File(Assets.get("mymidifile.midi"))); however there is no File constructor that would take a ByteArray. Suggestions, please?

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  • C# to Java: where T : new() Syntax

    - by Shiftbit
    I am porting some C# code over to Java. I am having trouble with the where Syntax, specifically new(). I understand that where is similar to Java's generic: T extends FOO. How I can replicate the new() argument in Java? "The new() Constraint lets the compiler know that any type argument supplied must have an accessible parameterless--or default-- constructor." - MSDN ie: public class BAR<T> : BAR where T : FOO, new() Right now I have: public class BAR<T extends FOO> extends ABSTRACTBAR { public HXIT(T t){ this.value = t; } .... }

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  • How can I get this code involving unique_ptr to compile?!

    - by Neil G
    #include <vector> #include <memory> using namespace std; class A { public: A(): i(new int) {} A(A const& a) = delete; A(A &&a): i(move(a.i)) {} unique_ptr<int> i; }; class AGroup { public: void AddA(A &&a) { a_.emplace_back(move(a)); } vector<A> a_; }; int main() { AGroup ag; ag.AddA(A()); return 0; } does not compile... (says that unique_ptr's copy constructor is deleted) I tried replacing move with forward. Not sure if I did it right, but it didn't work for me.

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  • What's the cause of (and treatment for) this java MySQL exception?

    - by justkevin
    I'm getting the following exception when executing the first preparedstatement after a period of inactivity: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 2,855,054 milliseconds ago. The last packet sent successfully to the server was 123 milliseconds ago. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3052) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2938) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3481) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2648) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2228) This only shows up if my application hasn't communicated with MySQL recently. Subsequent queries execute normally. I suspect it's some kind of timeout issue, but the periods of inactivity are way below the 8 hour timeout for MySQL. Any suggestions?

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