inheritance

问题 As we know everything in Javascript inherits from Object : So if I create an object using constructor function like below: function Rabbit() { this.color = 'White' } let obj = new Rabbit(); alert(Rabbit.__proto__ === Function.prototype) //true alert(obj.__proto__ === Rabbit.prototype) //true alert(obj.__proto__.__proto__ === Object.prototype) //true alert(Function.__proto__ === Object.prototype) //false alert(Object.getPrototypeOf(Function) === Object.getPrototypeOf(Object)) //true The first

问题 As we know everything in Javascript inherits from Object : So if I create an object using constructor function like below: function Rabbit() { this.color = 'White' } let obj = new Rabbit(); alert(Rabbit.__proto__ === Function.prototype) //true alert(obj.__proto__ === Rabbit.prototype) //true alert(obj.__proto__.__proto__ === Object.prototype) //true alert(Function.__proto__ === Object.prototype) //false alert(Object.getPrototypeOf(Function) === Object.getPrototypeOf(Object)) //true The first

问题 I have a generic list class that implements a particular interface. The list items in the interface also implement the same interface. public abstract class List<T extends SomeInterface> implements SomeInterface { protected LinkedList<T> m_list; ... } So now I want to make a subclass of this list that stays generic but limits the items to objects that implement the SearchListItem interface: public interface SearchListItem { public String getName(); } Here's what I have for the SearchList

问题 I am wondering if you can store items into a vector, using the emplace_back, a type that is derived from the class that vector expects. For example: struct fruit { std::string name; std::string color; }; struct apple : fruit { apple() : fruit("Apple", "Red") { } }; Somewhere else: std::vector<fruit> fruits; I want to store an object of type apple inside the vector. Is this possible? 回答1: No. A vector only stores elements of a fixed type. You want a pointer to an object: #include <memory>

问题 I know about the Strategy and Abstract Factory design patterns - however they don't solve my current problem: I'm creating a C++ library that offers a very basic GUI. However I want the user to be able to choose at compile time which GUI library to use (say Qt or FLTK) to actually render the GUI. The user should however only need to know about the methods in my library. It should be possible to compile the same code without any changes using either a Qt backend or an FLTK backend. I thought

问题 I know about the Strategy and Abstract Factory design patterns - however they don't solve my current problem: I'm creating a C++ library that offers a very basic GUI. However I want the user to be able to choose at compile time which GUI library to use (say Qt or FLTK) to actually render the GUI. The user should however only need to know about the methods in my library. It should be possible to compile the same code without any changes using either a Qt backend or an FLTK backend. I thought

问题 I have this structures in C++11 struct A { int idA; void setId(int i) { idA = i;} int getId() { return idA;} virtual void foo() = 0; }; struct B { int idB; void setId(int i) { idB = i;} int getId() { return idB;} virtual void foo2() = 0; }; struct AB : public A, public B { void foo() override {} void foo2() override {} }; Now in main I can call it like this: AB * ab = new AB(); ab->B::setId(10); but I dont really like it. Is there any other solution? Methods setId/getId from struct A are not

问题 Overriding static field in derived class causes error TS2417: Build:Class static side 'typeof TDerived' incorrectly extends base class static side 'typeof TBase'. Is this a legit error case? class TBase { private static s_field = 'something'; public constructor() {} } class TDerived extends TBase { private static s_field = 'something else'; // commenting this line fixes error public constructor() { super(); } } How should i deal with static fields then? The only workaround right now would be

问题 I am getting an unexplained difference in behavior between using super().__init__() and explicitly calling a super class constructor in my code. class IPElement(object): def __init__(self, ip_type='IPv4'): self.ip_type = ip_type class IPAddressSimple(IPElement): def __init__(self, ip_name, ip_type='IPv4'): self.ip_name = ip_name super().__init__(self, ip_type=ip_type) Here, the line super().__init__(self, ip_type=ip_type) results in a type error: TypeError: __init__() got multiple values for

问题 I have a problem with inheriting a custom generic. The compiler (Visual Studio for Mac), complaints that the inheriting generic can't be implicitly converted to another, inheriting type. A break down of my code is as follows: I have an interface called IAnsweredCommon and another interface that inherits from it called IAnsweredAndroid public interface IAnsweredCommon and public interface IAnsweredAndroid : IAnsweredCommon I have two other classes that use these interfaces. public abstract