inheritance

问题 I am using Visual Studio 2008 and have two classes Parent and Child. Parent declares some static const variables in the header, which are then defined in the cpp file. When I try to use the defines as cases in a switch statement in a child class I get the error: C2051: case expression not constant . So I've done some testing and the behavior I'm seeing is somewhat inconsistent. // Parent.h class Parent { public: Parent(); ~Parent(void) { } static const unsigned long A = 1; static const

问题 I have one super class Field and there are two other classes that inherit the super class Field . I want to dynamically add subclass without affecting super class changes public class TestConfiguration { private List<Field> fields; } I want to use the mapping in this way when fields is instance of same class Field then without className property "Field" used for mapping { "fields" : [ { "name" : "First_name", "type" : { "fieldType" : { "name" : "string" } }, "required" : true }] } I want to

问题 Since Dijkstra's algorithm and Prim's algorithm are so similar, I'd like to make a base algorithm class (I'll call it "Greedy" or something) and then I want to inherit from Greedy and tweak the algorithm based on the class. I think it boils down to this. I'd like to reuse a large portion of an algorithm but tweak an operation or two. class BaseAlg { public: BaseAlg(std::vector<int> data) //constructor sums a vector and stores result { int accum = 0; for (unsigned int i = 0; i < data.size(); +

问题 I am trying to emulate inheritance in javascript using a the Lo-Dash javascript library. I am simply using _.extend to do so: function Parent() { var self = this; self.hello = function () { console.log('Hello from parent'); }; } function Child() { var self = this; _.extend(self, Parent); } Child.hello(); // Doesn't exist I thought this would work since all javascript functions are objects but obviously I am wrong. Why doesn't this work and how would I properly emulate inheritance using Lo

问题 I am trying to emulate inheritance in javascript using a the Lo-Dash javascript library. I am simply using _.extend to do so: function Parent() { var self = this; self.hello = function () { console.log('Hello from parent'); }; } function Child() { var self = this; _.extend(self, Parent); } Child.hello(); // Doesn't exist I thought this would work since all javascript functions are objects but obviously I am wrong. Why doesn't this work and how would I properly emulate inheritance using Lo

问题 So I've been trying to find the proper way to get what should be pretty straightforward inheritance to function (the way I want ;)) and I'm failing miserably. Consider this: class Parent { public String name = "Parent"; public Parent() {}; public void doStuff() { System.out.println(name); } } class Child extends Parent { public String name = "Child"; public Child() { doStuff(); } } I understand that Java doesn't do what I'd expect in this case as for some reason member variables aren't

问题 So I've been trying to find the proper way to get what should be pretty straightforward inheritance to function (the way I want ;)) and I'm failing miserably. Consider this: class Parent { public String name = "Parent"; public Parent() {}; public void doStuff() { System.out.println(name); } } class Child extends Parent { public String name = "Child"; public Child() { doStuff(); } } I understand that Java doesn't do what I'd expect in this case as for some reason member variables aren't

问题 Is it possible to access base class public member from instance of derived class in some other locations in the program. class base { public: int x; base(int xx){ x = xx; } }; class derived : base { public: derived(int xx) : base(xx){ } }; class main { public: derived * myDerived; void m1(){ myDerived = new derived(5); m2(myDerived); } void m2(derived * myDerived){ printf("%i", myDerived->x); } }; After above code, I got following error. `error: 'int base::x' is inaccessible` 回答1: You inherit

问题 Is it possible to access base class public member from instance of derived class in some other locations in the program. class base { public: int x; base(int xx){ x = xx; } }; class derived : base { public: derived(int xx) : base(xx){ } }; class main { public: derived * myDerived; void m1(){ myDerived = new derived(5); m2(myDerived); } void m2(derived * myDerived){ printf("%i", myDerived->x); } }; After above code, I got following error. `error: 'int base::x' is inaccessible` 回答1: You inherit

问题 I'm trying to export a class and its base class from a DLL like this: #ifdef MY_EXPORTS #define DECLSPEC_TEST __declspec(dllexport) #else #define DECLSPEC_TEST __declspec(dllimport) #endif class DECLSPEC_TEST BaseClass { // stuff. }; class DECLSPEC_TEST DerivedClass : public BaseClass { // This class only has a constructor which initializes the class differently. }; But I try to use this class in another DLL, I keep getting an error: error LNK2019: unresolved external symbol "__declspec