inheritance

问题 I'm working on a huge project that I didn't start. My task is to add some additional functionality to what already is there. I'm in a situation where I have to use virtual inheritance because I have a diamond model. The situation is depicted in the following illustration: Base class / \ / \ My new class A class that was there before (OldClass) \ / \ / \ / \ / My other new class For this to work, both the classes in the middle have to inherit from the base through public virtual instead of

问题 Suppose I define a function on an abstract type A in Julia: abstract A function mysum(a::A) a.x + a.y end Implicitly any subtype should have the fields x and y for this function to work. So the functions defined on A are what set the requirements for subtypes. These functions could be written anywhere and one can imagine a situation where the functions are much more complex and the requirements are harder to spot. Is there someway to declare the requirements a subtype of an abstract type must

问题 Suppose I define a function on an abstract type A in Julia: abstract A function mysum(a::A) a.x + a.y end Implicitly any subtype should have the fields x and y for this function to work. So the functions defined on A are what set the requirements for subtypes. These functions could be written anywhere and one can imagine a situation where the functions are much more complex and the requirements are harder to spot. Is there someway to declare the requirements a subtype of an abstract type must

问题 In Generics class A<T extends Number> is allowed But class A<T super Integer> is not allowed I'm not getting this point. This may sound like novice question but I'm stuck in it 回答1: Quoting Java Generics: extends, super and wildcards explained: The super bound is not allowed in class definition. //this code does not compile ! class Forbidden<X super Vehicle> { } Why? Because such construction doesn't make sense. For example, you can't erase the type parameter with Vehicle because the class

问题 I feel like I skipped a C# class or two, but here's my dilemma: I have an abstract class from which I derive multiple child classes. I know for sure that for each of the child classes I will have a constructor that needs a certain static object as a model and this object will be different for each of the child classes. My first approach was to make a public static object in the abstract parent class and then, before I start creating any instances of the child classes, I would modify it for

问题 I have the following code: function Shape(x, y) { this.x = x; this.y = y; } Shape.prototype.describeLocation = function() { return 'I am located at ' + this.x + ', ' + this.y; }; var myShape = new Shape(1, 2); function Circle(x, y, radius) { Shape.call(this, x, y); // call parent constructor this.radius = radius; } var myFirstCircle = new Circle(3, 4, 10); Circle.prototype = Object.create(Shape.prototype); Circle.prototype.calculateArea = function() { return 'My area is ' + (Math.PI * this

问题 Well there is enough information about this subject. For example this thread was very clear to me: Difference between private, public, and protected inheritance Except one point; Why is it useful? 回答1: Use public inheritance to reflect an is-a relationship . This is the main use for inheritance, especially in combination with virtual functions. It allows re-use of interface, not just of old code by new code, but also re-use of new code by old code! (because of virtual function dispatch at

问题 Well there is enough information about this subject. For example this thread was very clear to me: Difference between private, public, and protected inheritance Except one point; Why is it useful? 回答1: Use public inheritance to reflect an is-a relationship . This is the main use for inheritance, especially in combination with virtual functions. It allows re-use of interface, not just of old code by new code, but also re-use of new code by old code! (because of virtual function dispatch at

问题 I'm glad C# doesn't let you access static members 'as though' they were instance members. This avoids a common bug in Java: Thread t = new Thread(..); t.sleep(..); //Probably doesn't do what the programmer intended. On the other hand, it does let you access static members 'through' derived types. Other than operators (where it saves you from writing casts), I can't think of any cases where this is actually helpful. In fact, it actively encourages mistakes such as: // Nasty surprises ahead -

问题 I'm using MVP pattern to develop a large scale application. While working in the development I have come up with the question whether if composition or inheritance should be used. For example: Let's assume that I have a form called Foo with fields A and B . In other part of the application I have a form Bar that has the same fields A and B but an additional field C . Currently, the code is written with the inheritance approach in where the view the form Bar inherits from form Foo . The