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  • doubt in - Function Objects - c++

    - by Eternal Learner
    I have a class class fobj{ public: fobj(int i):id(i) {} void operator()() { std::cout<<"Prints"<<std::endl; } private: int id; }; template<typename T> void func(T type) { type(); } My Doubt is if I invoke func like Method 1: func(fobj(1); the message I wanted to print is printed. I was always thinking I needed to do something like Method 2: fobj Iobj(1); // create an instance of the fobj class func(Iobj); //call func by passing Iobj(which is a function object) How does Method 1 work? I mean what exactly happens? and how is a call made to the operator() in class fobj ?

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  • What to prefer in the following case?

    - by GK
    say suppose I have class as : public class Age { private int age; public int getAge() { return this.age; } } In my Main class I am calling the getAge() method many times. So I wanted to know is it advisable to call so many times or call once and assign it to some variable and use that variable. Which is best and why?

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  • Dynamic class_name for has_many relations

    - by vooD
    I'm trying to make has_many relation with dynamic class_name attribute class Category < ActiveRecord::Base has_many :ads, :class_name => ( lambda { return self.item_type } ) end or class Category < ActiveRecord::Base has_many :ads, :class_name => self.item_type end But i got errors: can't convert Proc into String or undefined method `item_type' for #<Class:0xb62c6c88> Thank you for any help!

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  • How do i get my search bar to actually work?

    - by Sam
    Hey guys, I've got a search bar and it looks fine, but i don't really know how to make it search the whole of my site... Here's my html code so far: <form class="search2" method="get" action="default.html" /> <input class="search2" type="text" name="serach_bar" size="31" maxlength="255" value="" style="left: 396px; top: 153px; width: 293px; height: 26px;" /> <input class="search1" type="submit" name="submition" value="Search" style=" padding- bottom:20px; left: 691px; top: 153px; height: 23px" /> <input class="search2" type="hidden" name="sitesearch" value="default.html" /> Thanks in advance guys!

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  • Three customer addresses in one table or in separate tables?

    - by DR
    In my application I have a Customer class and an Address class. The Customer class has three instances of the Address class: customerAddress, deliveryAddress, invoiceAddress. Whats the best way to reflect this structure in a database? The straightforward way would be a customer table and a separate address table. A more denormalized way would be just a customer table with columns for every address (Example for "street": customer_street, delivery_street, invoice_street) What are your experiences with that? Are there any advantages and disadvantages of these approaches?

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  • How can I avoid huge communication classes in WCF?

    - by mafutrct
    My understanding is that all contract-implementing code has to be in a single class, that can become very large, obviously. How do I avoid this? I really prefer to have a few small classes doing one part of the communication with clients than a single behemoth class. The only idea I could think of is using multiple interfaces implemented by a single class split up by partial, but I don't this this is really solving the issue.

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  • Constructor initialising an array of subobjects?

    - by ojw
    Say I have several objects within a class, each of which needs constructing with a different value. I can write something like this: class b { public: b(int num) { // 1 for a.b1, and 2 for a.b2 } }; class a { public: b b1; b b2; a() : b1(1), b2(2) { } }; However, is it possible to do the same thing if those multiple objects are stored in an array? My first attempt at it doesn't compile: class a { public: b bb[2]; a() : bb[0](1), bb[1](2) { } };

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  • Misunderstanding function pointer - passing it as an argument

    - by Stef
    I want to pass a member function of class A to class B via a function pointer as argument. Please advise whether this road is leading somewhere and help me fill the pothole. #include <iostream> using namespace std; class A{ public: int dosomeA(int x){ cout<< "doing some A to "<<x <<endl; return(0); } }; class B{ public: B(int (*ptr)(int)){ptr(0);}; }; int main() { A a; int (*APtr)(int)=&A::dosomeA; B b(APtr); return 0; } This brilliant piece of code leaves me with the compiler error: cannot convert int (A::*)(int)' toint (*)(int)' in initialization Firstly I want it to compile. Secondly I don't want dosomeA to be STATIC.

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  • Asp.net static object behaviour

    - by Circadian
    I have the following class as part of an asp.net application. public sealed class SomeClass { private static string appId = Guid.NewGuid().ToString(); public static ReadSomethingFromDb(){} public static WriteSomethingToDb(){} } There are more than one application instances in the same application pool, and they all access the same database. I want the operations performed by the above class to be uniquely tied to the instance that performed it, hence the use of the appId. So adding a record to the database would for example contain a name, address and appId. This has been simplified for discussion purposes. Assuming that I have two instances running at mysite.a and mysite.b the above class would generate two different guids. My problem is that mysite.a sometimes produces more than one guid, which is unexpected. Thank you in advance

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  • Android HTTP get methods

    - by Nick
    I have written a number of applications for blackberry and am just starting in Android. It seems to me that android has a lot more built in functions. I am starting by recreating some of my BB apps on Android and on one I take a few xml sites and parse them out. On blackberry I implemented this by creating a class that extended a thread. I would construct a new instance of this class with the parameters of my http request and it would call a function back in my main class, sending it the results. I am tempted to reuse my code, but am curious if android has something better built in. I have been looking at the handler class as well as possible using a service. Bascially, I would like to start a new thread that will return a document of a specific url. Thanks!

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  • Design classes/interface to support methods returning different types

    - by Nayn
    Hi, I have classes as below. public interface ITest <T> { public T MethodHere(); } public class test1 implements ITest<String> { String MethodHere(){ return "Bla"; } } public class test2 implements ITest<Integer> { Integer MethodHere(){ return Integer.valueOf(2); } } public class ITestFactory { public static ITest getInstance(int type) { if(type == 1) return new test1(); else if(type == 2) return new test2(); } } There is a warning in the factory class that ITest is used as raw type. What modification should I do to get rid of it? Thanks Nayn

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  • Boost singleton trouble

    - by Ockonal
    Hi guys, I have some class which uses boost singleton. It calls some function from own c++ library. This library is written in make file as dependence. Now I have another singleton class and it should call first singleton class. After this code I got linkers error about undefined references for functions which are used in first singleton. When I remove calling first singleton class from second the errors remove. Maybe there is something wrong?

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  • The pImpl idiom and Testability

    - by Rimo
    The pImpl idiom in c++ aims to hide the implementation details (=private members) of a class from the users of that class. However it also hides some of the dependencies of that class which is usually regarded bad from a testing point of view. For example if class A hides its implementation details in Class AImpl which is only accessible from A.cpp and AImpl depends on a lot of other classes, it becomes very difficult to unit test class A since the testing framework has no access to the methods of AImpl and also no way to inject dependency into AImpl. This has been a problem for me lately and I am beginning to think that the pImpl idiom and writing testable code don't mix well. Has anyone come across this problem before? and have you found a solution?

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  • jquery XML, i need .html() not .text() but not working?

    - by Xtian
    I need var long to be exported as html and not text. I know I have .text() but when I use .html() it will not work. Also if I take the .text() out when declaring the variable and it will not work in IE? The reason for this is, in the XML certain words will have html tags like or and I need those to be recognized. I thought I solved it when I took out .text() but then i looked at IE and I got nothing. $(document).ready(function(){ $.ajax({ type: "GET", url: "xml/sites.xml", dataType: "xml", success: function(xml) { $(xml).find('site').each(function(){ var id = $(this).attr('id'); var title = $(this).find('title').text(); var class =$(this).find('class').text(); $('<div class="'+class+'" id="link_'+id+'"></div>').html('<h2>'+title+'</h2>').appendTo('#page-wrap'); $(this).find('desc').each(function(){ var long = $(this).find('long'); var url = $(this).find('url').text(); $('<div class="long"></div>').html(long).appendTo('#link_'+id); $('<a href="http://'+url+'"</a>').html(url).appendTo('#link_'+id); }); }); } }); });// JavaScript Document

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  • as3 this.graphics calls do nothing

    - by zzz
    class A: [SWF(width='800',height='600',frameRate='24')] public class A extends MovieClip { private var b:B; public function A(){ super(); b = new B(); addChild(b); addEventListener(Event.ENTER_FRAME, update); } private function update(e:Event):void { b.draw(); } } class B: public class B extends MovieClip { public function draw():void { //! following code works well if put in constructor, but not here this.graphics.beginFill(0xff0000); this.graphics.drawCircle(200,200,50); } } this.graphics calls do nothing in draw method, but work fine inside B`s constructor, what i am doing wrong ?

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  • jQueryUI widget text plus icon

    - by cf_PhillipSenn
    I have: <div class="ui-widget"> <div class="ui-widget-header"> My Menu<span class="ui-icon ui-icon-circle-triangle-n"></span> </div> <ul class="ui-widget-content"> <li>Menu Item 1</li> <li>Menu Item 2</li> <li>Menu Item 3</li> </ul> </div> Right now, the ui-icon is appearing below "My Menu" Q: How can I get "My Menu" to appear on the same line as the UI widget?

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  • Calling child constructor by casting (ChildClass)parentObject; to track revisions

    - by FreshCode
    To track revisions of a Page class, I have a PageRevision class which inherits from Page and adds a revision ID (Guid RevisionID;). If possible, how should I cast an existing Page object to a PageRevision and ensure that the PageRevision constructor is called to create a new revision ID? I could could have a PageRevision(Page page) constructor which generates the Guid and copies all the Page attributes, but I want to automate it, especially if a Page class has many attributes (and I later add one, and forget to modify the copy constructor). Desired use Page page = new Page(123, "Page Title", "Page Body"); // where 123 is page ID PageRevision revision = (PageRevision)page; // now revision.RevisionID should be a new Guid. Page, PageRevision classes: public class Page { public int ID { get; set; } public string Title { get; set; } public string Body { get; set; } } public class PageRevision : Page { public Guid RevisionID { get; set; } public PageRevision() { this.RevisionID = Guid.NewGuid(); } }

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  • null reference problems with c#

    - by alex
    Hi: In one of my window form, I created an instance of a class to do some works in the background. I wanted to capture the debug messages in that class and displayed in the textbox in the window form. Here is what I did: class A //window form class { public void startBackGroundTask() { B backGroundTask = new B(this); } public void updateTextBox(string data) { if (data != null) { if (this.Textbox.InvokeRequired) { appendUIDelegate updateDelegate = new appendUIDelegate(updateUI); try { this.Invoke(updateDelegate, data); } catch (Exception e) { Console.WriteLine(e.Message); } } else { updateUI(data); } } } private void updateUI(string data) { if (this.Textbox.InvokeRequired) { this.Textbox.Invoke(new appendUIDelegate(this.updateUI), data); } else { //update the text box this.Textbox.AppendText(data); this.Textbox.AppendText(Environment.NewLine); } } private delegate void appendUIDelegate(string data); } class B // background task { A curUI; public b( A UI) { curUI = UI; } private void test() { //do some works here then log the debug message to UI. curUI.updateTextBox("message); } } I keep getting a null reference exception after this.Invoke(updateDelegate, data); is called. I know passing "this" as a parameter is strange. But I want to send the debug message to my window form. Please help. Thanks

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  • Unable to run JAR file (created in Eclipse)

    - by Trist
    I hate starting a post with this but I'm new to Java... I've followed this tutorial to create a socket server (mines in Eclipse). I can run the server within Eclipse, all is well. But when I try to export the project I can't figure out how to run it. I keep getting this error (it varies depending on how I run it) Exception in thread "main" java.lang.NoClassDefFoundError: xsocketserver/Main Caused by: java.lang.ClassNotFoundException: xsocketserver.Main at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) I've read this problem relates to class paths being set. I've tried the following: java -cp libs/xSocket-2.8.12.jar xsocketserver.Main java -jar xSocketServer.jar java -classpath xSocketServer:xSocketServer/libs/xSocket-2.8.12.jar xsocketserver.Main plus many others. The file structure within the JAR is as follows: xSocketServer.jar -> xsocketserver -> Main.class -> xSocketDataHandler.class -> META-INF -> MANIFEST.MF -> libs -> xSocket-2.8.12.jar Incidentally I've tried adding my own manifest file which contains the Class-Path but when I check it it always reads: Manifest-Version: 1.0 Main-Class: xsocketserver.Main I'm guessing this is a common problem based on the number of hits I've seen in Google but I can't fathom what I'm doing wrong. Wrong Export settings maybe??

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  • Extending abstract classes in c#

    - by ng
    I am a Java developer and I have noticed some differences in extending abstract classes in c# as opposed to Java. I was wondering how a c# developer would achived the following. 1) Covarience public abstract class A { public abstract List<B> List(); } public class BList : List<T> where T : B { } public abstract class C : A { public abstract BList List(); } So in the above hierarchy, there is covarience in C where it returns a type compatible with what A returns. However this gives me an error in Visual Studio. Is there a way to specify a covarient return type in c#? 2) Adding a setter to a property public abstract class A { public abstract String Name { get; } } public abstract class B : A { public abstract String Name { get; set } } Here the compiler complains of hiding. Any suggestions? Please do not suggest using interfaces unless that is the ONLY way to do this.

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  • final fields and thread-safety

    - by pcjuzer
    Should it be all fields, including super-fields, of a purposively immutable java class 'final' in order to be thread-safe or is it enough to have no modifier methods? Suppose I have a POJO with non-final fields where all fields are type of some immutable class. This POJO has getters-setters, and a constructor wich sets some initial value. If I extend this POJO with knocking out modifier methods, thus making it immutable, will extension class be thread-safe?

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  • Objects with inheritance memory storage

    - by nikitas350
    Say that i have some classes like this example. class A { int k, m; public: A(int a, int b) { k = a; m = b; } }; class B { int k, m; public: B() { k = 2; m = 3; } }; class C : private A, private B { int k, m; public: C(int a, int b) : A(a, b) { k = b; m = a; } }; Now, in a class C object, are the variables stored in a specific way? I know what happens in a POD object, but this is not a POD object...

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  • java.util.Observable, will clients complete executing their update() before continuing

    - by jax
    When I call: setChanged(); notifyObservers() on a java.until.Observable class, will all the listening Observer objects complete execution of their udpate() methods - assuming we are running in the same Thread - before the java.until.Observable class continues running? This is important because I will be sending a few messages through the notifyObservers(Object o) method in quick concession, it is important that each Observer class has finished its method before the new one though. I understand that the order of execution for each Observer class may vary when we call notifyObservers() - it is just important that the order of method execution for each individual instance is in order.

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  • Calling a constructor to reinitialize variables doesn't seem to work?

    - by Matt
    I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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