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• Dynamic inheritance/implementation in PHP 5.*

  - by Rolf

  Hi everyone, I'm implementing a Logger, based on a XML declaration (path to class, method name, custom log message). There is also a Logger interface that defines the function __call, the latter logs what's needed and then relays the call to the target method. The only difficulty is to make each class, declared in the XML file, implement this interface with __call. So finally my question: is there a way to set at runtime the parent class or the implemented interface of another class ? Thanks in advance ! Rolf

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• WPF Window Inheritance

  - by Jonathan Sternberg

  I have an application that will run in two modes, each with very similar displays. The application is supposed to allow easy modification of a user interface. One of the features is that it has to display the user interface. Both of these windows look the same, just one has more menus than the other. I'd like to just create a base template (the user visual) and then inherit it for the editor. That way if one interface changes, both of them change. But this doesn't seem to be possible using WPF. I try to inherit and I get warnings about hiding members. I also don't see how I'm going to append new menus to the base template. Is what I'm trying to do possible? Is there a better way that I'm supposed to be doing this? It seems like I'm fighting the way that they want me to make the application.

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• inheritance from str or int

  - by wiso

  Why I have problem creating a class the inherite from str (or also int) class C(str): def __init__(self, a, b): str.__init__(self,a) self.b = b C("a", "B") TypeError: str() takes at most 1 argument (2 given) tha same appened if I try to use int instead of str, but it works with custom classes. I need to use __new__ instead of __init__? why?

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• Question about design (inheritance, polymorphism)

  - by Dan

  Hi, I have a question about a problem I'm struggling with. Hope you can bear with me. Imagine I have an Object class representing the base class of a hierarchy of physical objects. Later I inherit from it to create an Object1D, Object2D and Object3D classes. Each of these derived classes will have some specific methods and attributes. For example, the 3d object might have functionality to download a 3d model to be used by a renderer. So I'd have something like this: class Object {}; class Object1D : public Object { Point mPos; }; class Object2D : public Object { ... }; class Object3D : public Object { Model mModel; }; Now I'd have a separate class called Renderer, which simply takes an Object as argument and well, renders it :-) In a similar way, I'd like to support different kinds of renderers. For instance, I could have a default one that every object could rely on, and then provide other specific renderers for some kind of objects: class Renderer {}; // Default one class Renderer3D : public Renderer {}; And here comes my problem. A renderer class needs to get an Object as an argument, for example in the constructor in order to retrieve whatever data it needs to render the object. So far so good. But a Renderer3D would need to get an Object3D argument, in order to get not only the basic attributes but also the specific attributes of a 3d object. Constructors would look like this: CRenderer(Object& object); CRenderer3D(Object3D& object); Now how do I specify this in a generic way? Or better yet, is there a better way to design this? I know I could rely on RTTI or similar but I'd like to avoid this if possible as I feel there is probably a better way to deal with this. Thanks in advance!

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• Vectors of Pointers, inheritance

  - by user308553

  Hi I am a C++ beginner just encountered a problem I don't know how to fix I have two class, this is the header file: class A { public: int i; A(int a); }; class B: public A { public: string str; B(int a, string b); }; then I want to create a vector in main which store either class A or class B vector<A*> vec; A objectOne(1); B objectTwo(2, "hi"); vec.push_back(&objectOne); vec.push_back(&objectTwo); cout << vec.at(1)->i; //this is fine cout << vec.at(1)->str; //ERROR here I am really confused, I checked sites and stuff but I just don't know how to fix it, please help thanks in advance

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• Question regarding inheritance in wxWidgets.

  - by celestialorb

  Currently I'm attempting to write my own wxObject, and I would like for the class to be based off of the wxTextCtrl class. Currently this is what I have: class CommandTextCtrl : public wxTextCtrl { public: void OnKey(wxKeyEvent& event); private: DECLARE_EVENT_TABLE() }; Then later on I have this line of code, which is doesn't like: CommandTextCtrl *ctrl = new CommandTextCtrl(panel, wxID_ANY, *placeholder, *origin, *size); ...and when I attempt to compile the program I receive this error: error: no matching function for call to ‘CommandTextCtrl::CommandTextCtrl(wxPanel*&, <anonymous enum>, const wxString&, const wxPoint&, const wxSize&)’ It seems that it doesn't inherit the constructor method with wxTextCtrl. Does anyone happen to know why it doesn't inherit the constructor? Thanks in advance for any help!

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• django templating system inheritance issue

  - by Suhail

  hi, i am having issues with my django templating system, i have a base.html file, which contains the content which will be common on all the web pages of the web site, the base.html file fetches some dynamic content, like the categories and the archives, which are passed to it by a python file, which fetches the categories and the archives data from a mysql database. the issue when i inherit this base.html file in other html files like index.html: {% extends "base.html" %} and when when i call the main index URL for ex: http://mywebsite.com/index/ the index page gets loaded, but the categories and the archives data that should get loaded from the base.html file does not. what am i doing wrong, please help.

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• Type casting in TPC inheritance

  - by Mohsen Esmailpour

  I have several products like HotelProduct, FlightProduct ... which derived from BaseProduct class. The table of these products will be generated in TPC manner in database. There is OrderLine class which has a BaseProduct. My problem is when i select an OrderLine with related product i don't know how cast BaseProduct to derived product. for example i have this query: var order = (from odr in _context.Orders join orderLine in _context.OrderLines on odr.Id equals orderLine.OrderId join hotel in _context.Products.OfType<HotelProduct>() on orderLine.ProductId equals hotel.Id where odr.UserId == userId && odr.Id == orderId orderby odr.OrderDate descending select odr).SingleOrDefault(); In OrderLine i have BaseProduct properties not properties of HotelProduct. Is there any way to cast BaseProduct to derived class in OrderLine or any other solutions ?

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• Inheritance in Java

  - by stevebot

  If I have an abstract class in java named Foo and it has an implementor named Bar then I want to know the following. lets say Foo looks something like public abstract class Foo { Service serviceFoo ... } And Bar is public class Bar extends Foo { ... } Also, lets assume I have an instance with Foo, named foo, currently that has serviceFoo instantiated If I then declare: Foo foo = new Bar(); will this create a a new instance of Bar that has serviceFoo instantiated or not? E.g. will that field be inherited and instantiated or just inherited?

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• Prototypal inheritance should save memory, right?

  - by Techpriester

  Hi Folks, I've been wondering: Using prototypes in JavaScript should be more memory efficient than attaching every member of an object directly to it for the following reasons: The prototype is just one single object. The instances hold only references to their prototype. Versus: Every instance holds a copy of all the members and methods that are defined by the constructor. I started a little experiment with this: var TestObjectFat = function() { this.number = 42; this.text = randomString(1000); } var TestObjectThin = function() { this.number = 42; } TestObjectThin.prototype.text = randomString(1000); randomString(x) just produces a, well, random String of length x. I then instantiated the objects in large quantities like this: var arr = new Array(); for (var i = 0; i < 1000; i++) { arr.push(new TestObjectFat()); // or new TestObjectThin() } ... and checked the memory usage of the browser process (Google Chrome). I know, that's not very exact... However, in both cases the memory usage went up significantly as expected (about 30MB for TestObjectFat), but the prototype variant used not much less memory (about 26MB for TestObjectThin). I also checked: The TestObjectThin instances contain the same string in their "text" property, so they are really using the property of the prototype. Now, I'm not so sure what to think about this. The prototyping doesn't seem to be the big memory saver at all. I know that prototyping is a great idea for many other reasons, but I'm specifically concerned with memory usage here. Any explanations why the prototype variant uses almost the same amount of memory? Am I missing something?

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• JAVA Inheritance Generics and Casting.

  - by James Moore

  Hello, I have two classes which both extends Example. public class ClassA extends Example { public ClassA() { super("a", "class"); } .... } public class ClassB extends Example { public ClassB() { super("b", "class"); } .... } public class Example () { public String get(String x, String y) { return "Hello"; } } So thats all very well. So suppose we have another class called ExampleManager. With example manager I want to use a generic type and consequently return that generic type. e.g. public class ExampleManager<T extends Example> { public T getExample() { return new T("example","example"); // So what exactly goes here? } } So where I am returning my generic type how do i get this to actually work correctly and cast Example as either classA or classB? Many Thanks

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• Using inheritance and polymorphism to solve a common game problem

  - by Barry Brown

  I have two classes; let's call them Ogre and Wizard. (All fields are public to make the example easier to type in.) public class Ogre { int weight; int height; int axeLength; } public class Wizard { int age; int IQ; int height; } In each class I can create a method called, say, battle() that will determine who will win if an Ogre meets and Ogre or a Wizard meets a Wizard. Here's an example. If an Ogre meets an Ogre, the heavier one wins. But if the weight is the same, the one with the longer axe wins. public Ogre battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else if (this.axeLength > o.axeLength) return this; else if (this.axeLength < o.axeLength) return o; else return this; // default case } We can make a similar method for Wizards. But what if a Wizard meets an Ogre? We could of course make a method for that, comparing, say, just the heights. public Wizard battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else return this; } And we'd make a similar one for Ogres that meet Wizard. But things get out of hand if we have to add more character types to the program. This is where I get stuck. One obvious solution is to create a Character class with the common traits. Ogre and Wizard inherit from the Character and extend it to include the other traits that define each one. public class Character { int height; public Character battle(Character c) { if (this.height > c.height) return this; else if (this.height < c.height) return c; else return this; } } Is there a better way to organize the classes? I've looked at the strategy pattern and the mediator pattern, but I'm not sure how either of them (if any) could help here. My goal is to reach some kind of common battle method, so that if an Ogre meets an Ogre it uses the Ogre-vs-Ogre battle, but if an Ogre meets a Wizard, it uses a more generic one. Further, what if the characters that meet share no common traits? How can we decide who wins a battle?

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• Strange inheritance behaviour in Objective-C

  - by Smikey

  Hi all, I've created a class called SelectableObject like so: #define kNumberKey @"Object" #define kNameKey @"Name" #define kThumbStringKey @"Thumb" #define kMainStringKey @"Main" #import <Foundation/Foundation.h> @interface SelectableObject : NSObject <NSCoding> { int number; NSString *name; NSString *thumbString; NSString *mainString; } @property (nonatomic, assign) int number; @property (nonatomic, retain) NSString *name; @property (nonatomic, retain) NSString *thumbString; @property (nonatomic, retain) NSString *mainString; @end So far so good. And the implementation section conforms to the NSCoding protocol as expected. HOWEVER, when I add a new class which inherits from this class, i.e. #import <Foundation/Foundation.h> #import "SelectableObject.h" @interface Pet : SelectableObject <NSCoding> { } @end I suddenly get the following compiler error in the Selectable object class! SelectableObject.h:16: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'interface' This makes no sense to me. Why is the interface declaration for the SelectableObject class suddenly broken? I also import it in a couple of other classes I've written... Any help would be very much appreciated. Thanks! Michael

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• Java inheritance and super() isn't working as expected

  - by dwwilson66

  For a homework assignment, I'm working with the following. It's an assigned class structure, I know it's not the best design by a long shot. Class | Extends | Variables -------------------------------------------------------- Person | None | firstName, lastName, streetAddress, zipCode, phone CollegeEmployee | Person | ssn, salary,deptName Faculty | CollegeEmployee | tenure(boolean) Student | person | GPA,major So in the Faculty class... public class Faculty extends CollegeEmployee { protected String booleanFlag; protected boolean tenured; public Faculty(String firstName, String lastName, String streetAddress, String zipCode, String phoneNumber,String ssn, String department,double salary) { super(firstName,lastName,streetAddress,zipCode,phoneNumber, ssn,department,salary); String booleanFlag = JOptionPane.showInputDialog (null, "Tenured (Y/N)?"); if(booleanFlag.equals("Y")) tenured = true; else tenured = false; } } It was my understanding that super() in Faculty would allow access to the variables in CollegeEmployee as well as Person. With the code above, it compiles fine when I ONLY include the Person variables. As soon as I try to use ssn, department, or salary I get the following compile errors. Faculty.java:15: error: constructor CollegeEmployee in class CollegeEmployee can not be applied to the given types: super(firstName,lastName,streetAddress,zipCode,phoneNumber,ssn,department,salary); ^ Required: String,String,String,String,String Found: String,String,String,String,String,String,String,String reason: actual and formal argument lists differ in length I'm completely confused by this error...which is the actual and formal? Person has five arguments, CollegeEmployee has 3, so my guess is that something's funky with how the parameters are being passed...but I'm not quite sure where to begin fixing it. What am I missing?

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• C# unusual inheritance syntax w/ generics

  - by anon

  I happened upon this in an NHibernate class definition: public class SQLiteConfiguration : PersistenceConfiguration<SQLiteConfiguration> So this class inherits from a base class that is parameterized by... the derived class?   My head just exploded. Can someone explain what this means and how this pattern is useful? (This is NOT an NHibernate-specific question, by the way.)

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• Form Inheritance in Visual Studios designer implementations

  - by CooPzZ

  I'm in the process of Moving a project from Visual Studio 2003 to 2005 and have just seen the The event Click is read-only and cannot be changed when using inherited forms regardless of the Modifier on the Base Forms Controls will make all the Controls from the Base Readonly in the designer (Though in 2003 it didn't work this way). I found this post metioning that this functionality has been temporarily" disabled http://social.msdn.microsoft.com/Forums/en-US/winformsdesigner/thread/c25cec28-67a5-4e30-bb2d-9f8dbd41eb3a Can anyone confirm whether this feature is used anymore? or how to program around it to be able to use the Base Control Events and still have a designer? This is one way I've found but quite painfull when it used to do the plumbing for you. even just hiding one of the controls you have manually do now. Public Class BFormChild Friend Overrides Sub cmdApply_Click(ByVal sender As Object, ByVal e As System.EventArgs) MyBase.cmdApply_Click(sender, e) End Sub Friend Overrides Sub cmdCancel_Click(ByVal sender As Object, ByVal e As System.EventArgs) MyBase.cmdCancel_Click(sender, e) End Sub Friend Overrides Sub cmdOk_Click(ByVal sender As Object, ByVal e As System.EventArgs) MyBase.cmdOk_Click(sender, e) End Sub End Class

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• Inheritance and choose constructor from base class

  - by myle

  My question is rather simple, but I am stuck. How can I choose the desired constructor from base class? // node.h #ifndef NODE_H #define NODE_H #include <vector> // definition of an exception-class class WrongBoundsException { }; class Node { public: ... Node(double, double, std::vector<double>&) throw (WrongBoundsException); ... }; #endif // InternalNode.h #ifndef INTERNALNODE_H #define INTERNALNODE_H #include <vector> #include "Node.h" class InternalNode : public Node { public: // the position of the leftmost child (child left) int left_child; // the position of the parent int parent; InternalNode(double, double, std::vector<double>&, int parent, int left_child) throw (WrongBoundsException); private: int abcd; }; #endif // InternalNode.cpp #include "InternalNode.h" #define UNDEFINED_CHILD -1 #define ROOT -1 // Here is the problem InternalNode::InternalNode(double a, double b, std::vector<double> &v, int par, int lc) throw (WrongBoundsException) : Node(a, b, v), parent(par), left_child(lc) { std::cout << par << std::endl; } I get: $ g++ InternalNode.cpp InternalNode.cpp:16: error: declaration of ‘InternalNode::InternalNode(double, double, std::vector &, int, int) throw (WrongBoundsException)’ throws different exceptions InternalNode.h:17: error: from previous declaration ‘InternalNode::InternalNode(double, double, std::vector &, int, int)’ UPDATE 0: Fixed missing : UPDATE 1: Fixed throw exception

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• Fun with casting and inheritance

  - by Vaccano

  NOTE: This question is written in a C# like pseudo code, but I am really going to ask which languages have a solution. Please don't get hung up on syntax. Say I have two classes: class AngleLabel: CustomLabel { public bool Bold; // code to allow the label to be on an angle } class Label: CustomLabel { public bool Bold; // Code for a normal label // Maybe has code not in an AngleLabel (align for example). } They both decend from this class: class CustomLabel: Control { protected bool Bold; } The bold field is exposed as public in the descended classes. No interfaces are available on the classes. Now, I have a method that I want to beable to pass in a CustomLabel and set the Bold property. Can this be done without having to 1) find out what the real class of the object is and 2) cast to that object and then 3) make seperate code for each variable of each label type to set bold. Kind of like this: public void SetBold(customLabel: CustomLabel) { AngleLabel angleLabel; NormalLabel normalLabel; if (angleLabel is AngleLabel ) { angleLabel= customLabel as AngleLabel angleLabel.Bold = true; } if (label is Label) { normalLabel = customLabel as Label normalLabel .Bold = true; } } It would be nice to maybe make one cast and and then set bold on one variable. What I was musing about was to make a fourth class that just exposes the bold variable and cast my custom label to that class. Would that work? If so, which languages would it work for? (This example is drawn from an old version of Delphi (Delphi 5)). I don't know if it would work for that language, (I still need to try it out) but I am curious if it would work for C++, C# or Java. If not, any ideas on what would work? (Remember no interfaces are provided and I can not modify the classes.) Any one have a guess?

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• Constructor Overload Problem in C++ Inheritance

  - by metdos

  Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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• C++ initializing constants and inheritance

  - by pingvinus

  I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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• C# template type inheritance

  - by Malki

  Hi, I want to create a template class in C#, for example: public class Foo<T> where T must inherit from a known class. I cant seem to find the syntax for that. Thanks, Malki.

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• A problem regarding dll inheritance

  - by Adam

  Hello all I have created a dll that will be used by multiple applications, and have created an installer package that installs it to the program files, as well as adds it to the Global Assembly Cache. The dll itself uses log4net, and requires a xml file for the logging definitions. Therefore when the installer is run, the following files get copied to the install directory within program files: The main dll that I developed - The Log4Net.dll - the Log4Net.xml file I am now experiencing a problem. I have created a test console application for experimentation. I have added my dll as a reference, and set the 'local copy' flag to false. When I compile the test console exe however, I noticed that it has copied the log4net.dll and log4net.xml files to the bin directory. And when running the test console, it appears that it will only work if the log4net.dll is in the same directory as the exe. This is dispite the fact that the test console application does not use log4net, only the dll that was added as a reference does. Is there some way to have it so that the log4net.dll & xml files used will be the ones that were installed to the program files, rather than any application needed to copy over local copies? The applications that will be using my dll will not be using log4net, only the dll that they are referencing uses it. Many thanks

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• inheritance problem OOP extend

  - by hsmit

  If a Father is a Parent and a Parent is a Person and a Person has a Father I create the following: class Person{ Father father; } class Parent extends Person{} class Father extends Parent{} Instances: Person p1 = new Person(); Person p2 = new Person(); p1.father = p2; //father is of the type Father This doesn't work... Now try casting:: Person p1 = new Person(); Person p2 = new Person(); p1.father = (Father)p2; This doesn't work either. What does work for this case?

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• Inheritance in XML Schema definition (XSD) for Java objects

  - by bguiz

  Hi, I need to create an XML schema definition (XSD) that describes Java objects. I was wondering how to do this when the objects in question inherit from a common base class with a type parameter. public abstract class Rule<T> { ... } public abstract class TimeRule extends Rule<XTime> { ... } public abstract class LocationRule extends Rule<Location> { ... } public abstract class IntRule extends Rule<Integer> { ... } .... (where XTime and Location are custom classes define elsewhere) How would I go about constructing an XSD that such that I can have XML nodes that represent each of the subclasses of Rule<T> - without the XSD for each of them repeating their common contents? Thank you!

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• Django Template Inheritance -- Missing Images?

  - by user367817

  Howdy, I have got the following file heirarchy: project   other stuff   templates       images           images for site       app1           templates for app1       registration           login template       base.html (base for entire site)       style.css (for base.html) In the login template, I am extending 'base.html.' 'base.html' uses 'style.css' along with all of the images in the 'templates/images' directory. For some reason, none of the CSS styles or images will show up in the login template, even though I'm extending it. Does this missing image issue have something to do with screwed up "media" settings somewhere? I never understood those, but this is a major roadblock in my proof-of-concept, so any help is appreciated. Thanks!

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