inheritance

问题 I am working on a wizard form framework that will allow me easily create wizard forms. I have a WizardForm form that has a panel on it. My plan is to dynamically load UserControls into this panel on the form. Each UserControl that is loaded onto the form panel must implement certain properties (allowNavigateNext, AllowNAvigate previous etc.). So I have created an interface to enforce that contract so that any custom user control can be used in the wizard as long as it implements that

问题 I'm trying to make this: class A { //attibutes } class B : A { public int classBAttribute = 5; // other attributes and methods } My question is this if I have an instance of A class how can i get the instance of the B class or access his attributes? B b = new B(); Application.Add(b); //other form A a = Application.GetA(); B b = getBFromA(a);// ??? Note: B b = a as B; does't work i tried 回答1: You cannot do this -- there is no magical way to create derived objects from base objects in general.

问题 I'm not sure if this is what it's called, but here is the problem: I have a superclass with three subclasses. Let's say Superclass, Subclass1, Subclass2,Subclass3 I have another class with the following overloaded method: public void exampleMethod (Subclass1 object1){ //Method to be called if the object is of subclass 1 } public void exampleMethod (Subclass2 object2){ //Method to be called if the object is of subclass 2 } public void exampleMethod (Subclass3 object3){ //Method to be called if

问题 In MatLab, i have a superclass A that takes some parameters, x and y classdef A < handle properties x; y; z; end methods function this = A(x, y) this.x = x; this.y = y; this.initialize(); end function initialize(this) this.z = this.x + this.y; end end end The initialize method is supposed to do some initial calculations to fasten computation later. Now i want to create a child class B of A, with it's own inialization, but B should be initialized before A. classdef B < A properties p end

问题 This may already have an answer but I've not been able to find an exact case of what I'm attempting. Suppose you have some generic variant-like class like so (irrelevant details omitted): /* in hpp file */ struct Base { void * data; Base(); virtual ~Base(); // ... virtual bool Read(...); } template <Some_Enum_Class T> struct Derived : Base { // T-specific interface to deal with Base::data bool Read(...); /* implementation in separate cpp file */ } For reasons specific to the project, it will

问题 Temp1 t1=new Temp2(); Here Temp1 is superclass of Temp2. The code works perfectly fine and t1 do acts as a reference variable for Temp1 but how can Temp2() works as constructor for Temp1? 回答1: This is the basis for polymorphism: Imagine you have several child classes that inherit from you parent class. You want to use all these child classes through the interface / methods defined on your parent class, without worrying about the implementation details in each child class (each might do

问题 I'm trying to use a custom collection to "connect" (or relate) two classes but I haven't been able to do it. Maybe I got the whole concept of the SqlAlchemy custom collections wrong, but let me explain what I am doing (and see if someone can give me a hint, or something) I have a Parent class (which some of you will remember from other questions) with a couple of connectors fields (kind of lists) in it. One of the connectors will store instances of a Child() class whose type is " VR " and the

问题 In C# I have a bunch of objects all inheriting from the same base class. I also have a number of Dictionaries, one for each subclass. What I want to do is add all of those Dictionaries to one List so I can loop through them all and do some work (like comparing the lists etc). In summary Dictionary<string, Child> childObjects = new Dictionary<string, Child>(); List<Dictionary<string, Parent>> listOfDictionaries = new List<Dictionary<string, Parent>>(); listOfDictionaries.Add(childObjects); I

问题 I'm learning object oriented programming in python and I'm not too sure how to write methods for classes My first question is, can you inherit two classes at the same time? Example: class A: def __init__ eg. storing list of strings class B: def __ init__ eg. storing list of strings # I want to inherit both class A and B into class C class C (A,B): Is this possible? many examples showed only inheritance from one class. Assuming that I can import the methods from both class A and class B , I

问题 Often when including namespaces or assemblies into my code, I often run into strange cases where a namespace is inherited from another, yet classes from the parent namespace are not available. For example, when using List<> or Dictionary<> , I use the System.Collections.Generic namespace. However, if I also want to use an IEnumerator , I also have to include the System.Collections namespace. Shouldn't System.Collections already be referenced by any member of System.Collections.Generic , as it