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  • Comparison between a value with static type Array and a possibly unrelated type Class

    - by Kaoru
    I got this error: Comparison between a value with static type Array and a possibly unrelated type Class. After i modify the class to many classes (before that, everything is on 1 class (all of the functions)), but after i move everything to many classes (all the functions is not on 1 class), that error appear. How to solve this? I am using AS3 and as3isolib Library. Here is the code after i modify the function: if (Constant.dude.y < Constant._numY) { if (Constant.dude.sprites != marioBackClass) { Constant.dude.sprites = [marioBackClass]; Constant.dudeDir = "Up"; } } Here is the code before i change the function to many classes: if (dude.y < ._numY) { if (dude.sprites.toString() != marioBackClass.toString()) { dude.sprites = [marioBackClass]; dudeDir = "Up"; } }

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  • SSIS Virtual Class

    - by ejohnson2010
    I recorded a Virtual SSIS Class with the good folks over at SSWUG and the first airing of the class will by May 15th. This is 100% online so you can do it on your own time and from anywhere. The class will run monthly and I will be available for questions through out. You get the following 12 sessions on SSIS, each about an hour. Session 1: The SSIS Basics Session 2: Control Flow Basics Session 3: Data Flow - Sources and Destinations Session 4: Data Flow - Transformations Session 5: Advanced Transformations...(read more)

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  • How to remove unused usings from class file ?

    - by Samir R. Bhogayta
    When we create a .cs file means code file class is automatically create. That .cs file means class has default usings for namespace. using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls; We don't use all namespaces  in that class so we have to remove unused namespaces from file. We can remove  namespace manually but it takes time and need full knowledge of class library so we can use Visual Studio . Step 1:  Right Click in .cs File. Step 2:  Move on Organize usings. Step 3: Click on Remove Unused Usings. After that we have only those namespaces in the file these are using.  

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  • Collision: Vector class (java)

    - by user8363
    When handling collision detection / response and you need a Vector class, do you need to create that class yourself or is there a java class you can use? A vector class should have methods like: subtract(Vector v), normalize(), dotProduct(Vector v), ... At the moment it seems logical to use classes like java.awt.Rectangle and java.awt.Polygon to calculate collisions. Would I be right to use these classes for this purpose? My question is not about how to implement collision detection, I know how that works. However I'm wondering what would be a correct and clean way to implement it in java since I'm fairly new to the language and to application development in general.

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  • New to Java Programming - Error help

    - by JJJ
    I am going through a Java book and drafting the examples and have run into the following error when compiling this code. Any help would be appreciated thank you. Error: Main.java:3: class Addition is public, should be declared in a file named Addition.java public class Addition        ^ 1 error Code: import java.io.*; import java.util.Scanner; public class Addition {   public static void main(String[] args) { java.util.Scanner input = new java.util.Scanner(System.in);  int number1; int number2; int sum; System.out.print( "Enter first digit: " ); number1 = input.nextInt(); System.out.print( "Enter second digit:" ); number2 = input.nextInt(); sum = number1 + number2; System.out.printf( "Sum is %d\n, sum" );      } }

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  • Collision Detection within Player/Enemy Class

    - by user1264811
    I'm making a 2D platform game. Right now I'm just working on making a very generic Player class. I'm wondering if it would be more efficient/better practice to have an ActionListener within the Player class to detect collisions with Enemy objects (also have an ActionListener) or to handle all the collisions in the main world. Furthermore, I'm thinking ahead about how I will handle collisions with the platforms themselves. I've looked into the double boolean arrays to see which tiles players can go to and which they can't. I don't understand how to use this class and the player class at the same time. Thank you.

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  • Should I implement an interface directly or have the superclass do it?

    - by c_maker
    Is there a difference between public class A extends AbstractB implements C {...} versus... public class A extends AbstractB {...} AbstractB implements C {...} I understand that in both cases, class A will end up conforming to the interface. In the second case, AbstractB can provide implementation for interface methods in C. Is that the only difference? If I do NOT want to provide an implementation for any of the interface methods in AbstractB, which style should I be using? Does using one or the other have some hidden 'documentation' purpose?

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  • OOP PHP make separate classes or one

    - by user2956219
    I'm studying OOP PHP and working on a small personal project but I have hard time grasping some concepts. Let's say I have a list of items, each item belongs to subcategory, and each subcategory belongs to category. So should I make separate classes for category (with methods to list all categories, add new category, delete category), class for subcategories and class for items? Or should I make creating, listing and deleting categories as methods for item class? Both category and subcategory are very simple and basically consist of ID, Name and parentID (for subcategory).

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  • The Path to Best-In-Class Service Business Performance

    - by Charles Knapp
    What would it matter to offer your customers best-in-class service and support experiences? According to a new study, best-in-class companies enjoy margins that are nearly double the average, retain almost all of their customers each year, deliver annual revenue growth that is six greater than average, and realize cost decreases rather than increases! What does it take to become best in class? Some of the keys are: Engage customers effectively and consistently across all channels Focus on mobility to improve reactive service performance Continue to transition from primarily reactive to proactive and predictive service performance Build the support structure for new services and service contracts Construct an engaged service delivery team Join the Aberdeen Group, Oracle, Infosys, and Hyundai Capital as we highlight the key stages in the service transformation journey and reveal how Best-in-Class organizations are equipping themselves to thrive in this new era of service. Please join us for "Service Excellence and the Path to Business Transformation" -- this Thursday, October 25, 8:00 AM PDT | 11:00 AM EDT | 3:00 PM GMT | 4:00 PM BST.

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  • C++ converting back and forth from derived and base classes

    - by user127817
    I was wondering if there is a way in C++ to accomplish the following: I have a base class called ResultBase and two class that are Derived from it, Variable and Expression. I have a few methods that do work on vector<ResultBase> . I want to be able to pass in vectors of Variable and Expression into these methods. I can achieve this by creating a vector<ResultBase> and using static_cast to fill it with the members from my vector of Variable/Expression. However, once the vector has run through the methods, I want to be able to get it back as the vector of Result/Expression. I'll know for sure which one I want back. static_cast won't work here as there isn't a method to reconstruct a Variable/Expression from a ResultBase, and more importantly I wouldn't have the original properties of the Variables/Expressions The methods modify some of the properties of the ResultBase and I need those changes to be reflected in the original vectors. (i.e. ResultBase has a property called IsLive, and one of the methods will modify this property. I want this IsLive value to be reflected in the derived class used to create the ResultBase Whats the easiest way to accomplish this?

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  • Extending the method pool of a concrete class which is derived by an interface

    - by CelGene
    Hello, I had created an interface to abstract a part of the source for a later extension. But what if I want to extend the derived classes with some special methods? So I have the interface here: class virtualFoo { public: virtual ~virtualFoo() { } virtual void create() = 0; virtual void initialize() = 0; }; and one derived class with an extra method: class concreteFoo : public virtualFoo { public: concreteFoo() { } ~concreteFoo() { } virtual void create() { } virtual void initialize() { } void ownMethod() { } }; So I try to create an Instance of concreteFoo and try to call ownMethod like this: void main() { virtualFoo* ptr = new concreteFoo(); concreteFoo* ptr2 = dynamic_cast(ptr); if(NULL != ptr2) ptr2->ownMethod(); } It works but is not really the elegant way. If I would try to use ptr-ownMethod(); directly the compiler complains that this method is not part of virtualFoo. Is there a chance to do this without using dynamic_cast? Thanks in advance!

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  • Google App Engine JDO how to define class fields ?

    - by Frank
    I have a class like this : import java.io.*; import java.util.*; public class Contact_Info_Entry implements Serializable { public static final long serialVersionUID=26362862L; String Contact_Id,First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country="",E_Mail="",Phone; int I_1,I_2; float F_1,F_2; boolean B_1,B_2; GregorianCalendar Date_1, Date_2; Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } If I want to translate it to a class for JDO, do I need to define each field by it self or can I do a group at a time ? For instance do I have to make it like this : @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) private Long id; @Persistent public static final long serialVersionUID=26362862L; @Persistent String Contact_Id; @Persistent String First_Name; @Persistent String Last_Name; ...... @Persistent int I_1; @Persistent int I_2; ... @Persistent float F_1; ... @Persistent boolean B_1; @Persistent boolean B_2; @Persistent GregorianCalendar Date_1; ... @Persistent Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } Or can I do a group at a time like this : @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) private Long id; @Persistent public static final long serialVersionUID=26362862L; @Persistent String Contact_Id,First_Name,Last_Name=""; ...... @Persistent int I_1=0,I_2=1; ... @Persistent float F_1; ... @Persistent boolean B_1,B_2; @Persistent GregorianCalendar Date_1; ... @Persistent Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } Or can I skip the "@Persistent" all together like this : import java.io.*; import java.util.*; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { public static final long serialVersionUID=26362862L; String Contact_Id,First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country="", E_Mail="",Phone; int I_1,I_2; float F_1,F_2; boolean B_1,B_2; GregorianCalendar Date_1, Date_2; Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } Which are correct ? Frank

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  • C++ template-function -> passing a template-class as template-argument

    - by SeMa
    Hello, i try to make intensive use of templates to wrap a factory class: The wrapping class (i.e. classA) gets the wrapped class (i.e. classB) via an template-argument to provide 'pluggability'. Additionally i have to provide an inner-class (innerA) that inherits from the wrapped inner-class (innerB). The problem is the following error-message of the g++ "gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)": sebastian@tecuhtli:~/Development/cppExercises/functionTemplate$ g++ -o test test.cpp test.cpp: In static member function ‘static classA<A>::innerA<iB>* classA<A>::createInnerAs(iB&) [with iB = int, A = classB]’: test.cpp:39: instantiated from here test.cpp:32: error: dependent-name ‘classA::innerA<>’ is parsed as a non-type, but instantiation yields a type test.cpp:32: note: say ‘typename classA::innerA<>’ if a type is meant As you can see in the definition of method createInnerBs, i intend to pass a non-type argument. So the use of typename is wrong! The code of test.cpp is below: class classB{ public: template < class iB> class innerB{ iB& ib; innerB(iB& b) :ib(b){} }; template<template <class> class classShell, class iB> static classShell<iB>* createInnerBs(iB& b){ // this function creates instances of innerB and its subclasses, // because B holds a certain allocator return new classShell<iB>(b); } }; template<class A> class classA{ // intention of this class is meant to be a pluggable interface // using templates for compile-time checking public: template <class iB> class innerA: A::template innerB<iB>{ innerA(iB& b) :A::template innerB<iB>(b){} }; template<class iB> static inline innerA<iB>* createInnerAs(iB& b){ return A::createInnerBs<classA<A>::template innerA<> >(b); // line 32: error occurs here } }; typedef classA<classB> usable; int main (int argc, char* argv[]){ int a = 5; usable::innerA<int>* myVar = usable::createInnerAs(a); return 0; } Please help me, i have been faced to this problem for several days. Is it just impossible, what i'm trying to do? Or did i forgot something? Thanks, Sebastian

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  • JQuery Hover li Show div which sits outside li structure

    - by Dave_Stott
    Hi everyone I'm currently trying to create a "mega" dropout menu using JQuery but have encountered an issue I'm yet to be able to resolve. At the moment I have the following HTML structure: <div id="TopNav" class="grid_16"> <ul class="cmsListMenuUL level0" id="TopNavMenu"> <li class="cmsListMenuLIcmsListMenuLI highlightedLI" id="TopNavMenu_Home"><a href="/"> <span class="text">Home</span></a></li> <li class="cmsListMenuLIfirst" id="TopNavMenu_0_1"><a href="/Key-Sectors.aspx" class="cmsListMenuLink"> <span class="text">Key Sectors</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_2"><a href="/Global-Brands.aspx" class="cmsListMenuLink"> <span class="text">Global Brands</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_3"><a href="/News---Features.aspx" class="cmsListMenuLink"> <span class="text">News &amp; Features</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_4"><a href="/Videos.aspx" class="cmsListMenuLink"> <span class="text">Videos</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_5"><a href="/Events.aspx" class="cmsListMenuLink"> <span class="text">Events</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_6"><a href="/Key-Cities.aspx" class="cmsListMenuLink"> <span class="text">Key Cities</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_7"><a href="/Doing-Business-in-Yorkshire.aspx" class="cmsListMenuLink"><span class="text">Doing Business in Yorkshire</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_8"><a href="/How-We-Can-Help.aspx" class="cmsListMenuLink"> <span class="text">How We Can Help</span></a></li> <li class="cmsListMenuLI" id="TopNavMenu_0_9"><a href="/Contact-Us.aspx" class="cmsListMenuLink"> <span class="text">Contact Us</span></a></li> </ul> </div> <div class="sectorsDropped"> <div class="floatLeft leftColumn"> <div class="parentItem" style="border-color: #0064BE;"> <a href="/Key-Sectors/Advanced-Engineering---Materials.aspx" class="parentItemContent"> Advanced Engineering &amp; Materials</a><div class="childItem"> <a href="/Key-Sectors/Advanced-Engineering---Materials/Nuclear.aspx">- Nuclear</a></div> <div class="childItem"> <a href="/Key-Sectors/Advanced-Engineering---Materials/Logistics---Infrastructure.aspx"> - Logistics &amp; Infrastructure</a></div> </div> <div class="parentItem" style="border-color: #FFB611;"> <a href="/Key-Sectors/Chemicals.aspx" class="parentItemContent">Chemicals</a></div> <div class="parentItem" style="border-color: #B7CC0B;"> <a href="/Key-Sectors/Environmental-Technologies.aspx" class="parentItemContent">Environmental Technologies</a><div class="childItem"> <a href="/Key-Sectors/Environmental-Technologies/Offshore-Wind.aspx">- Offshore Wind</a></div> <div class="childItem"> <a href="/Key-Sectors/Environmental-Technologies/Carbon-Capture---Storage.aspx">- Carbon Capture &amp; Storage</a></div> <div class="childItem"> <a href="/Key-Sectors/Environmental-Technologies/Tidal-Power.aspx">- Tidal Power</a></div> <div class="childItem"> <a href="/Key-Sectors/Environmental-Technologies/Biomass.aspx">- Biomass</a></div> </div> </div> <div class="floatLeft rightColumn"> <div class="parentItem" style="border-color: #AC26AA;"> <a href="/Key-Sectors/Digital---New-Media.aspx" class="parentItemContent">Digital &amp; New Media</a></div> <div class="parentItem" style="border-color: #e1477e;"> <a href="/Key-Sectors/Food---Drink.aspx" class="parentItemContent">Food &amp; Drink</a></div> <div class="parentItem" style="border-color: #00c5b5;"> <a href="/Key-Sectors/Healthcare-Technologies.aspx" class="parentItemContent">Healthcare Technologies</a><div class="childItem"> <a href="/Key-Sectors/Healthcare-Technologies/Biotechnology.aspx">- Biotechnology</a></div> <div class="childItem"> <a href="/Key-Sectors/Healthcare-Technologies/Pharmaceuticals.aspx">- Pharmaceuticals</a></div> <div class="childItem"> <a href="/Key-Sectors/Healthcare-Technologies/Medical-Devices.aspx">- Medical Devices</a></div> </div> <div class="parentItem" style="border-color: #AC1A2F;"> <a href="/Key-Sectors/Financial---Professional.aspx" class="parentItemContent">Financial &amp; Professional</a></div> </div> </div> In normal circumstances the div containing the "mega" menu options would sit inside the li item that fires the show/hide but this is currently not possible as the ul list of navigation links is rendered using a 3rd party piece of software which does not provide an equivalent of an OnItemDataBound event for me to be able to inject the div into the item Does anyone know of a way, using JQuery, of showing the div but maintain the display of the div as the mouse focus leaves the li that originaly displayed the div and actually enters the div? I'm currently using the following JQuery which displays the div correctly but as the mouse focus enters the div the div then disappears as the mouse focus from the li has now moved: $(document).ready(function() { function addMega(){ $(".sectorsDropped").toggle("fast"); } function removeMega(){ $(".sectorsDropped").toggle("fast"); } var megaConfig = { interval: 500, sensitivity: 4, over: addMega, timeout: 500, out: removeMega }; $("#TopNavMenu_0_1").hoverIntent(megaConfig) }); Thanks Dave

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  • jQuery multiple class selection

    - by morpheous
    I am a bit confused with this: I have a page with a set of buttons (i.e. elements with class attribute 'button'. The buttons belong to one of two classes (grp1 and grp2). These are my requirements For buttons with class enabled, when the mouse hovers over them, a 'button-hover' class is added to them (i.e. the element the mouse is hovering over). Otherwise, the hover event is ignored When one of the buttons with class grp2 is clicked on (it has to be 'enabled' first), then I disable (i.e. remove the 'enabled' class for all elements with class 'enabled' (should probably selecting for elements with class 'button' AND 'enabled' - but I am having enough problems as it is, so I need to keep things simple for now). This is what my page looks like: <html> <head> <title>Demo</title> <style type="text/css" .button {border: 1px solid gray; color: gray} .enabled {border: 1px solid red; color: red} .button-hover {background-color: blue; } </style> <script type="text/javascript" src="jquery.js"></script> </head> <body> <div class="btn-cntnr"> <span class="grp1 button enabled">button 1</span> <span class="grp2 button enabled">button 2</span> <span class="grp2 button enabled">button 3</span> <span class="grp2 button enabled">button 4</span> </div> <script type="text/javascript"> /* <![CDATA[ */ $(document).ready(function(){ $(".button.enabled").hover(function(){ $(this).toggleClass('button-hover'); }, function() { $(this).toggleClass('button-hover'); }); $('.grp2.enabled').click(function(){ $(".grp2").removeClass('enabled');} }); /* ]]> */ </script> </body> </html> Currently, when a button with class 'grp2' is clicked on, the other elements with class 'grp2' have the 'enabled' class removed (works correctly). HOWEVER, I notice that even though the class no longer have a 'enabled' class, SOMEHOW, the hover behaviour is still applied to these elemets (WRONG). Once an element has been 'disabled', I no longer want it to respond to the hover() event. How may I implement this behavior, and what is wrong with the code above (i.e. why is it not working? (I am still learning jQuery)

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  • Safe to cast pointer to a forward-declared class to its true base class in C++?

    - by Matt DiMeo
    In one header file I have: #include "BaseClass.h" // a forward declaration of DerivedClass, which extends class BaseClass. class DerivedClass ; class Foo { DerivedClass *derived ; void someMethod() { // this is the cast I'm worried about. ((BaseClass*)derived)->baseClassMethod() ; } }; Now, DerivedClass is (in its own header file) derived from BaseClass, but the compiler doesn't know that at the time it's reading the definition above for class Foo. However, Foo refers to DerivedClass pointers and DerivedClass refers to Foo pointers, so they can't both know each other's declaration. First question is whether it's safe (according to C++ spec, not in any given compiler) to cast a derived class pointer to its base class pointer type in the absence of a full definition of the derived class. Second question is whether there's a better approach. I'm aware I could move someMethod()'s body out of the class definition, but in this case it's important that it be inlined (part of an actual, measured hotspot - I'm not guessing).

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  • C++ Add this pointer to a container by calling it in base class constructor

    - by vivekeviv
    class Base { public: Base (int a, int b); private: int a,b; }; class Derived1 { public: Derived1():base(1,2){} }; similarly Derived2, Derived 3 which doesnt contain any data members on its own Now i need to contain these derived objects in a singleton, so i was thinking to call this in base constructor like Base::Base(int a, int b) { CBaseMgr::GetInstance()->AddtoVector(this); } so now if i construct Derived d1, d2, d3 etc. will the Singleton's container contain all derived objects? My doubt is can i do this adding of objects to container in base ctor or should i do in derived ctor.?

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  • How to use a derived ControlTemplate in WPF

    - by Frank Fella
    The following xaml code works: <Window x:Class="DerivedTemplateBug.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:DerivedTemplateBug" Title="Window1" Height="300" Width="300"> <Button> <Button.Template> <ControlTemplate> <Border BorderBrush="Black" BorderThickness="2"> <TextBlock>Testing!</TextBlock> </Border> </ControlTemplate> </Button.Template> </Button> </Window> Now, if you define the following data template: using System.Windows.Controls; namespace DerivedTemplateBug { public class DerivedTemplate : ControlTemplate { } } And then swap the ControlTemplate for the derived class: <Window x:Class="DerivedTemplateBug.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:DerivedTemplateBug" Title="Window1" Height="300" Width="300"> <Button> <Button.Template> <local:DerivedTemplate> <Border BorderBrush="Black" BorderThickness="2"> <TextBlock>Testing!</TextBlock> </Border> </local:DerivedTemplate> </Button.Template> </Button> </Window> You get the following error: Invalid ContentPropertyAttribute on type 'DerivedTemplateBug.DerivedTemplate', property 'Content' not found. Can anyone tell my why this is the case?

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  • How can I create object in abstract class without having knowledge of implementation?

    - by Greg
    Hi, Is there a way to implement the "CreateNode" method in my library abstract below? Or can this only be done in client code outside the library? I current get the error "Cannot create an instance of the abstract class or interface 'ToplogyLibrary.AbstractNode" public abstract class AbstractTopology<T> { // Properties public Dictionary<T, AbstractNode<T>> Nodes { get; private set; } public List<AbstractRelationship<T>> Relationships { get; private set; } // Constructors protected AbstractTopology() { Nodes = new Dictionary<T, AbstractNode<T>>(); } // Methods public AbstractNode<T> CreateNode() { var node = new AbstractNode<T>(); // ** Does not work ** Nodes.Add(node.Key, node); } } } public abstract class AbstractNode<T> { public T Key { get; set; } } public abstract class AbstractRelationship<T> { public AbstractNode<T> Parent { get; set; } public AbstractNode<T> Child { get; set; } }

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  • Finding parent class and id

    - by Breezer
    Well after countless tries i can't get this work? <script type="text/javascript"> $("td input").focusout(function() { var column = $(this).parent('td').attr('class'); var row = $(this).parent('tr').attr('id'); $('#dat').HTML(row+" "+column); }); </script> And the html looks like this <tr class="numbers" id="1"> <td class="a" align="right">1</td> <td class="b"><input class="input" type="text" value=""/></td> <td class="c"><input class="input" type="text" value=""/></td> <td class="d"><input class="input" type="text" value=""/></td> <td class="e"><input class="input" type="text" value=""/></td> <td class="f">0</td> <td class="g"><input class="input" type="text" value=""/></td> </tr> can anyone point me to the right direction on what might be wrong? thanks in advance regards

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  • Apples, oranges, and pointers to the most derived c++ class

    - by Matthew Lowe
    Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest(f,p); } OK, wait. Stop right there. Note at this point that any sane person would make Eat() a virtual member function of the Fruit classes. But that's not an option, because I am not a sane person. Also, I don't want that Pesticide* in the header file for my fruit class. Sadly, what I want to be able to do next is exactly what member functions and dynamic binding allow: typedef list<Fruit*> Fruits; Fruits fs; ... for(Fruits::iterator i=fs.begin(), e=fs.end(); i!=e; ++i) Eat(*i); And obviously, the problem here is that the pointer we pass to Eat() will be a Fruit*, not an Apple* or an Orange*, therefore nothing will get eaten and we will all be very hungry. So what I really want to be able to do instead of this: Eat(*i); is this: Eat(MAGIC_CAST_TO_MOST_DERIVED_CLASS(*i)); But to my limited knowledge, such magic does not exist, except possibly in the form of a big nasty if-statement full of calls to dynamic_cast. So is there some run-time magic of which I am not aware? Or should I implement and maintain a big nasty if-statement full of dynamic_casts? Or should I suck it up, quit thinking about how I would implement this in Ruby, and allow a little Pesticide to make its way into my fruit header?

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  • Java Class<T> static method forName() IncompatibleClassChangeError

    - by matt
    Hi, i have this code: private static Importable getRightInstance(String s) throws Exception { Class<? extends Importable> c = Class.forName(s).asSubclass(Importable.class); Importable i = c.newInstance(); return i; } which i can also write private static Importable getRightInstance(String s) throws Exception { Class<? extends Importable> c = (Class<? extends Importable>)Class.forName(s); Importable i = c.newInstance(); return i; } or private static Importable getRightInstance(String s) throws Exception { Class<?> c = Class.forName(s); Importable i = (Importable)c.newInstance(); return i; } where Importable is an interface and s is a string representing an implementing class. Well, in any case it gives the following: Exception in thread "main" java.lang.IncompatibleClassChangeError: class C1 has interface Importable as super class Here is the last snippet of the stack trace: at java.lang.Class.forName(Class.java:169) at Importer.getRightImportable(Importer.java:33) at Importer.importAll(Importer.java:44) at Test.main(Test.java:16) Now, class C1 actually implemens Importable and i totally don't understand why it complaints. Thanks in advance.

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