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  • C# - Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new { _t = new T(); private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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  • C++ - checking if a class has a certain method at compile time

    - by jetwolf
    Here's a question for the C++ gurus out there. Is there a way to check at compile time where a type has a certain method, and do one thing if it does, and another thing if it doesn't? Basically, I have a template function template <typename T> void function(T t); and I it to behave a certain way if T has a method g(), and another way if it doesn't. Perhaps there is something that can be used together with boost's enable_if? Something like this: template <typename T> enable_if<has_method<T, g, void ()>, void>::type function(T t) { // Superior implementation calling t.g() } template <typename T> disable_if<has_method<T, g, void ()>, void>::type function(T t) { // Inferior implementation in the case where T doesn't have a method g() } "has_method" would be something that preferably checks both that T has a method named 'g', and that the method has the correct signature (in this case, void ()). Any ideas?

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  • c++ property class structure

    - by Without me Its just Aweso
    I have a c++ project being developed in QT. The problem I'm running in to is I am wanting to have a single base class that all my property classes inherit from so that I can store them all together. Right now I have: class AbstractProperty { public: AbstractProperty(QString propertyName); virtual QString toString() const = 0; virtual QString getName() = 0; virtual void fromString(QString str) = 0; virtual int toInteger() = 0; virtual bool operator==(const AbstractProperty &rightHand) = 0; virtual bool operator!=(const AbstractProperty &rightHand) = 0; virtual bool operator<(const AbstractProperty &rightHand) = 0; virtual bool operator>(const AbstractProperty &rightHand) = 0; virtual bool operator>=(const AbstractProperty &rightHand) = 0; virtual bool operator<=(const AbstractProperty &rightHand) = 0; protected: QString name; }; then I am implementing classes such as PropertyFloat and PropertyString and providing implementation for the comparator operators based on the assumption that only strings are being compared with strings and so on. However the problem with this is there would be no compiletime error thrown if i did if(propertyfloat a < propertystring b) however my implementation of the operators for each derived class relies on them both being the same derived class. So my problem is I cant figure out how to implement a property structure so that I can have them all inherit from some base type but code like what I have above would throw a compile time error. Any ideas on how this can be done? For those familiar with QT I tried using also a implementation with QVariant however QVariant doesn't have operators < and defined in itself only in some of its derived classes so it didn't work out. What my end goal is, is to be able to generically refer to properties. I have an element class that holds a hashmap of properties with string 'name' as key and the AbstractProperty as value. I want to be able to generically operate on the properties. i.e. if I want to get the max and min values of a property given its string name I have methods that are completely generic that will pull out the associated AbstactProperty from each element and find the max/min no matter what the type is. so properties although initially declared as PropertyFloat/PropertyString they will be held generically.

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  • How to calculate median of a Map<Int,Int>?

    - by Chris
    For a map where the key represents a number of a sequence and the value the count how often this number appeared in the squence, how would an implementation of an algorithm in java look like to calculate the median? For example: 1,1,2,2,2,2,3,3,3,4,5,6,6,6,7,7 in a map: Map<Int,Int> map = ... map.put(1,2) map.put(2,4) map.put(3,3) map.put(4,1) map.put(5,1) map.put(6,3) map.put(7,2) double median = calculateMedian(map); print(median); would result in: > print(median); 3 > So what i am looking for is a java implementation of calculateMedian.

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  • ActionScript 2: Event doesn't fire?

    - by Pascal Schuster
    So I have a soundHandler class that's supposed to play sounds and then point back to a function on the timeline when the sound has completed playing. But somehow, only one of the sounds plays when I try it out. EDIT: After that sound plays, nothing happens, even though I have EventHandlers set up that are supposed to do something. Here's the code: import mx.events.EventDispatcher; class soundHandler { private var dispatchEvent:Function; public var addEventListener:Function; public var removeEventListener:Function; var soundToPlay; var soundpath:String; var soundtype:String; var prefix:String; var mcname:String; public function soundHandler(soundpath:String, prefix:String, soundtype:String, mcname:String) { EventDispatcher.initialize(this); _root.createEmptyMovieClip(mcname, 1); this.soundpath = soundpath; this.soundtype = soundtype; this.prefix = prefix; this.mcname = mcname; } function playSound(file, callbackfunc) { _root.soundToPlay = new Sound(_root.mcname); _global.soundCallbackfunc = callbackfunc; _root.soundToPlay.onLoad = function(success:Boolean) { if (success) { _root.soundToPlay.start(); } }; _root.soundToPlay.onSoundComplete = function():Void { trace("Sound Complete: "+this.soundtype+this.prefix+this.file+".mp3"); trace(arguments.caller); dispatchEvent({type:_global.soundCallbackfunc}); trace(this.toString()); trace(this.callbackfunction); }; _root.soundToPlay.loadSound("../sound/"+soundpath+"/"+soundtype+prefix+file+".mp3", true); _root.soundToPlay.stop(); } } Here's the code from the .fla file: var playSounds:soundHandler = new soundHandler("signup", "su", "s", "mcs1"); var file = "000"; playSounds.addEventListener("sixtyseconds", this); playSounds.addEventListener("transition", this); function sixtyseconds() { trace("I am being called! Sixtyseconds"); var phase = 1; var file = random(6); if (file == 0) { file = 1; } if (file<10) { file = "0"+file; } file = phase+file; playSounds.playSound(file, "transition"); } function transition() { trace("this works"); } playSounds.playSound(file, "sixtyseconds"); I'm at a total loss for this one. Have been wasting hours to figure it out already. Any help will be deeply appreciated.

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  • How to use the variable declared in one class in another class in Obj C.

    - by srikanth rongali
    I have a NSDate *date1 in class1 implementation file(I initialized it as Global variable). I have NSDate *date2 in class 2 implementation file (initialized it as Global variable). I need to calculate the NSTimeInterval between the two dates in class 2. But I could not do it. I could not access date1 in this class. It is giving error as (date2 undeclared). Please give me help in how to call other class variables in this class. Thank you.

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  • What does "static" mean in the context of declaring global template functions?

    - by smf68
    I know what static means in the context of declaring global non-template functions (see e.g. What is a "static" function?), which is useful if you write a helper function in a header that is included from several different locations and want to avoid "duplicate definition" errors. So my question is: What does static mean in the context of declaring global template functions? Please note that I'm specifically asking about global, non-member template functions that do not belong to a class. In other words, what is the difference between the following two: template <typename T> void foo(T t) { /* implementation of foo here */ } template <typename T> static void bar(T t) { /* implementation of bar here */ }

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  • Domain-Driven-Design question

    - by Michael
    Hello everyone, I have a question about DDD. I'm building a application to learn DDD and I have a question about layering. I have an application that works like this: UI layer calls = Application Layer - Domain Layer - Database Here is a small example of how the code looks: //****************UI LAYER************************ //Uses Ioc to get the service from the factory. //This factory would be in the MyApp.Infrastructure.dll IImplementationFactory factory = new ImplementationFactory(); //Interface and implementation for Shopping Cart service would be in MyApp.ApplicationLayer.dll IShoppingCartService service = factory.GetImplementationFactory<IShoppingCartService>(); //This is the UI layer, //Calling into Application Layer //to get the shopping cart for a user. //Interface for IShoppingCart would be in MyApp.ApplicationLayer.dll //and implementation for IShoppingCart would be in MyApp.Model. IShoppingCart shoppingCart = service.GetShoppingCartByUserName(userName); //Show shopping cart information. //For example, items bought, price, taxes..etc ... //Pressed Purchase button, so even for when //button is pressed. //Uses Ioc to get the service from the factory again. IImplementationFactory factory = new ImplementationFactory(); IShoppingCartService service = factory.GetImplementationFactory<IShoppingCartService>(); service.Purchase(shoppingCart); //**********************Application Layer********************** public class ShoppingCartService : IShoppingCartService { public IShoppingCart GetShoppingCartByUserName(string userName) { //Uses Ioc to get the service from the factory. //This factory would be in the MyApp.Infrastructure.dll IImplementationFactory factory = new ImplementationFactory(); //Interface for repository would be in MyApp.Infrastructure.dll //but implementation would by in MyApp.Model.dll IShoppingCartRepository repository = factory.GetImplementationFactory<IShoppingCartRepository>(); IShoppingCart shoppingCart = repository.GetShoppingCartByUserName(username); //Do shopping cart logic like calculating taxes and stuff //I would put these in services but not sure? ... return shoppingCart; } public void Purchase(IShoppingCart shoppingCart) { //Do Purchase logic and calling out to repository ... } } I've seem to put most of my business rules in services rather than the models and I'm not sure if this is correct? Also, i'm not completely sure if I have the laying correct? Do I have the right pieces in the correct place? Also should my models leave my domain model? In general I'm I doing this correct according DDD? Thanks!

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  • When did the idea of macros (user-defined code transformation) appear?

    - by Jay
    I have read McCarthy's 1960 paper on LISP and found no reference to anything that's similar to user-defined macros or normal order evaluation. I was wondering when marcos first appeared in programming language history (and also in Lisp history): When was the idea of user-defined code transformation (before interpretation or compilation) first described (theoretically)? What was the first programming language implementation to have Lisp-like macros (by "Lisp-like" I mean "using a readable Turing-complete language to do code-transformation")? (including non-Lisps -- Forth for example is quite old, but I'm not sure if the first Forth implementation already had "IMMEDIATE") What was the first Lisp dialect to have macros? Thank you!

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  • The standard map/associative-array structure to use in flash actionscript 3?

    - by tstyle
    I'm relatively new to flash, and is confused about what I should use to store and retrieve key value pairs. After some googling I've found various map-like things to choose from: 1) Use a Object: var map:Object = new Object(); map["key"] = "value"; The problem is that it seems to lack some very basic features. For example to even get the size of map I'd have to write a util method. 2) Use a Dictionary What does this standard library class provide over the simple object? It seems silly for it to exist if it's functionally identical to Object. 3) Go download some custom HashMap/HashTable implementation from the web. I've used a lot of modern languages, and this is the first time I haven't been able to find a library implementation of an associative array within 5 minutes. So I'd like to get some best-practice advice from an experienced flash developer. Thanks!

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  • UIWebView appears null when calling fro a method

    - by Alexidze
    I have a major problem when trying to access a UIWebView that was created during ViewDidLoad, the UIWebView appears null here is how i declare the property @property (nonatomic, retain) UIWebView *detailsView; the implementation @implementation iPadMainViewController @synthesize detailsView; - (void)viewDidLoad { [super viewDidLoad]; detailsView = [[UIWebView alloc] initWithFrame:CGRectMake(500, 0, 512, 768)]; [self.view addSubView:detailsView]; } When accessing from - (void)loadDetailedContent:(NSString *)s { NSLog(@"%@", detailsView); } I get NULL, is it a normal behavior or am i doing something wrong? here is the touchesBegan that is being called, from the views subclass that is being touched, -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { iPadMainViewController *mycontroller = [[iPadMainViewController alloc] init]; self.delegate = mycontroller; [self.delegate loadDetailedContent:NewsId]; }

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  • Unexpected result from reduce function

    - by StackedCrooked
    I would like to get the smallest element from a vector. For this I use combine the reduce and min functions. However, when providing my own implementation of min I get unexpected results: user=> (reduce (fn [x y] (< x y) x y) [1 2 3 2 1 0 1 2]) 2 user=> (reduce min [1 2 3 2 1 0 1 2 3]) 0 The reduce with standard min returns 0 as expected. However, when I provide my own implementation it returns 2. What am I doing wrong?

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  • Should I combine unrelated interfaces into a single library?

    - by mafutrct
    Situation is like this: There are independent 5 services. Each service consists of a project for interface, implementation and test. Example: LocalizationService.Interfaces LocalizationService.Implementation LocalizationService.Test There is a WCF service for each of the services: LocalizationService.WcfContract (including DataContracts) LocalizationService.WcfHost The client applications are probably mostly going to use all of the services. Should I combine all service interfaces into a common one? AllServices.AllInterfaces In my opinion, this is a bad idea. The services are independent and there is no reason to introduce a dependency. I imagine that especially testing becomes more difficult. However, one may argue that having to include 5 libraries is too much of a hassle. (I'm not sure how to tag this. Feel free to retag.)

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  • What is the best way to expose a callback API - C++

    - by rursw1
    Hi, I have a C++ library that should expose some system\ resource calls as callbacks from the linked application. For example: the interfacing application (which uses this library) can send socket management callback functions - send, receive, open, close etc., and the library will use this implementation in stead of the library's implementation. (This way enables the application to manage the sockets by itself, can be useful). This library has to expose also more callbacks, like, for example, a password validation, so I wonder if there is a preferred method to expose the callback sending option in one API. Something like: int AddCallbackFunc (int functionCallbackType, <generic function prototype>, <generic way to pass some additional arguments>) Then within my library I will assign the callback to the appropriate function pointer according to the functionCallbackType parameter. Is there any way to implement it in a generic way which will fit ANY function prototype and ANY additional arguments? Your help will be more than appreciated... Thanks!

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  • build-helper-maven-plugin add-source does not working when trying to add linked resources

    - by Julian
    I am new to maven and hit a problem that looks easy in the first place but I already kept me busy for a whole day about and no way to get it working. First as part of running eclipse:eclipse plugin I create a linked folder like below: <linkedResources> <linkedResource> <name>properties</name> <type>2</type> <location>${PARENT-2-PROJECT_LOC}/some_other_project/properties</location> </linkedResource> <linkedResource> <name>properties/messages.properties</name> <type>1</type> <location>${PARENT-2-PROJECT_LOC}/some_other_project/properties/messages.properties</location> </linkedResource> And then I am adding that folder as a source folder like below: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>build-helper-maven-plugin</artifactId> <version>1.7</version> <executions> <execution> <id>add-source</id> <phase>generate-sources</phase> <goals> <goal>add-source</goal> </goals> <configuration> <sources> <source>properties</source> <source>some_real_folder</source> </sources> </configuration> </execution> </executions> </plugin> However when I am looking at the generated .classpath in eclipse the “some_real_folder” is there but the “properties” is not. It looks like by default the build-helper-maven-plugin will check if the folder is there and if it is not it won’t add it. I am using maven 3.0.4 outside eclipse to run the build and I can see in the maven logs something like this: [INFO] Source directory: <some path>\properties added. This is my project structure: project1 \-- properties (this is the real folder) project2 \-- some_real_folder \-- properties (this is the link resource pointing to the project1/properties folder) All I need is to have both "some_real_folder" and the linked resource "properties" added to the .classpath of the project2

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  • Creating design document from existing java code.

    - by BigBoss
    I have existing java code and need to create Design Document based on that. For starter even if I could get all functions with input / output parameters that will help in overall proces. Note: There is not commeted documentation on any procedures, function or classes. Last but not least. Let me know for any good tool which will reduce time required for this phase. As currently we write every flow and related stuffs.

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  • Change highlighting of certain subviews in a UITableViewCell

    - by SpacyRicochet
    Is it possible to exclude certain subviews in a UITableViewCell from being highlighted or to change their highlight implementation? I added an orange warning label to the UITableViewCell for certain occassions and it highlights properly with the rest of the cell, which is good. However, when the cells stops being highlighted in an animated way, you first see the background of the warning label become white and then flash to orange. I would either like it to be excluded from being highlighted at all, or to change it's highlight implementation so it animates back to orange properly.

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  • How to remove thie ".svc" extension in RESTful WCF service?

    - by Morgan Cheng
    In my knowledge, the RESTful WCF still has ".svc" in its URL. For example, if the service interface is like [OperationContract] [WebGet(UriTemplate = "/Value/{value}")] string GetDataStr(string value); The access URI is like "http://machinename/Service.svc/Value/2". In my understanding, part of REST advantage is that it can hide the implementation details. A RESTful URI like "http://machinename/Service/value/2" can be implemented by any RESTful framework, but a "http://machinename/Service.svc/value/2" exposes its implementation is WCF. How can I remove this ".svc" host in the access URI?

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  • Submitting form in php file accessed by Ajax?

    - by dronnoc
    Hi people, I am trying to figure out how to submit a form in a page being accessed by Ajax? here are some code snippets to help demonstrate what i am trying to say. HTML BODY - THIS IS WHAT THE USER WILL SEE. <html> <head> <script language="javascript" src="linktoajaxfile.js"> </head> <body onLoad="gotoPage(0)"> <div id="fillThis"> </div> </body> </html> AJAX FILE var xmlhttp function gotoPage(phase) { xmlhttp=GetXmlHttpObject(); if (xmlhttp==null) { alert ("Your browser does not support AJAX!"); return; } var url="pageofstuffce.php"; url=url+"?stg="+phase; url=url+"&sid="+Math.random(); xmlhttp.onreadystatechange=stateChanged; xmlhttp.open("GET",url,true); xmlhttp.send(null); } function stateChanged() { if (xmlhttp.readyState==4) { document.getElementById("fillThis").innerHTML=xmlhttp.responseText; } } function GetXmlHttpObject() { if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari return new XMLHttpRequest(); } if (window.ActiveXObject) { // code for IE6, IE5 return new ActiveXObject("Microsoft.XMLHTTP"); } return null; } PAGE OF DATA <?php $stage = $_GET['stg']; if($stage == 0) { echo '<a onClick="gotoPage(1)">click me</a>'; } elseif($stage == 1) { <form> <input type="text" name="name"> <input type="submit" name="submit"> </form> } elseif(somehow can reach here) { show data from form. } ?> Can anyone perhaps help me get past the form and display the data in the same page? Also, i have looked around, and i don't think anything around has what i need... correct me if i'm wrong though :) Thanks in advance, and i hope i didn't put in too much detail :) Dronnoc EDIT Forgot to mention what I've tried; I have tried submitting the form to itself (same file) and that destroyed the ajax link, and opened the page. i have also tried just having the button move the page onto another step, but the $_POST variable is empty... i am at a loss, so does anyone else have any ideas?

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  • boost::this_thread::disable_interruption usage confusion

    - by Evgenii
    boost/thread/pthread/shared_mutex.hpp contains this code: ... #include <boost/thread/detail/thread_interruption.hpp> ... class shared_mutex { ... void lock_shared() { boost::this_thread::disable_interruption do_not_disturb; boost::mutex::scoped_lock lk(state_change); while(state.exclusive || state.exclusive_waiting_blocked) { shared_cond.wait(lk); } ++state.shared_count; } ... }; but boost/thread/detail/thread_interruption.hpp does not contain implementation of disable_interruption, only the prototype. in boost_1_42_0/libs/thread/src/pthread we don't have the implementation too how does it work!???

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  • So where is this calling super?

    - by dontWatchMyProfile
    From the Core Data docs: Inheritance If you have two subclasses of NSManagedObject where the parent class implements a dynamic property and its subclass (the grandchild of NSManagedObject) overrides the methods for the property, those overrides cannot call super. @interface Parent : NSManagedObject @property(nonatomic, retain) NSString* parentString; @end @implementation Parent @dynamic parentString; @end @interface Child : Parent @end @implementation Child - (NSString *)parentString { // this throws a "selector not found" exception return parentString.foo; } @end very, very funny, because: I see nobody calling super. Or are they? Wait... parentString.foo results in ... a crash ??? it's a string. How can that thing have a .foo suffixed to it? Just another documentation bug?

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  • Why this friend function can't access a private member of the class?

    - by Alceu Costa
    I am getting the following error when I try to access bins private member of the GHistogram class from within the extractHistogram() implementation: error: 'QVector<double> MyNamespace::GHistogram::bins' is private error: within this context Where the 'within this context' error points to the extractHistogram() implementation. Does anyone knows what's wrong with my friend function declaration? Here's the code: namespace MyNamespace{ class GHistogram { public: GHistogram(qint32 numberOfBins); qint32 getNumberOfBins(); /** * Returns the frequency of the value i. */ double getValueAt(qint32 i); friend GHistogram * Gbdi::extractHistogram(GImage *image, qint32 numberOfBins); private: QVector<double> bins; }; GHistogram * extractHistogram(GImage * image, qint32 numberOfBins); }

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  • Basic View Switch Code Crashes iPhone simulator

    - by Ouija
    I've been trying to switch two views from two separate view controllers for a while and it never works, the simulator always crashes to the home screen. I'm using Xcode 3.2.5 and this is my code - SwitchViewsViewController.h #import <UIKit/UIKit.h> #import "SecondViewController.h" @interface SwitchViewsViewController : UIViewController { } -(IBAction)pushButton; @end SwitchViewsViewController.m #import "SwitchViewsViewController.h" #import "SecondViewController.h" @implementation SwitchViewsViewController -(IBAction)pushButton { SecondViewController *screen = [[SecondViewController alloc] initWithNibName:nil bundle:nil screen.modalTransitionStyle = UIModalTransitionStyleCoverVertical; [self presentModalViewController:screen animated:YES] [screen release]; } SecondViewController.h #import <UIKit/UIKit.h> @interface SecondViewController : UIViewController { } -(IBAction)pushBack; @end SecondViewController.m #import "SecondViewController.h" @implementation SecondViewController -(IBAction)pushBack{ [self dismissModalViewControllerAnimated:YES]; } In interface builder, all i've done is linked the file's owner classes and the buttons. Also made the SwitchViewsViewController load first, and not MainWindow. Everything builds but when I try to run the app it crashes and sends it to the home screen. Can anyone help me with this?

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