inheritance

问题 I have the Child class that extends Parent class. So let say I created a new instance "child" out of the Child class. When I check the condition child instanceof Child , it returns false. However, child instanceof Parent returns true. Why does this so? EDIT So I found this only happens when I extend the Child class with Error class. Let me leave the code example below. class Child extends Error { constructor(message) { super(message); } } const ch = new Child(); console.log(ch instanceof

问题 I am learning OOPs with python. created below code to replicate the diamond shape problem in multiple inheritence. I am running the below code in jupyter notebook and output is generated at same. class parent: def __init__(self): self.a=2 self.b=4 def form1(self): print("calling parent from1") print('p',self.a+self.b) class child1(parent): def __init__(self): self.a=50 self.b=4 def form1(self): print('bye',self.a-self.b) def callchildform1(self): print("calling parent from child1") super()

问题 I am in the process of switching over from DataTable to BindingList. I bind the DataTable to the DataGrid object. Here my dilemma: while I certainly see the advantages of switching over, my circumstances will make it a bit complex and I am wondering whether it is worth it to switch over. My scenario: I have a DataGrid which displays chemical samples. There are 5 kinds of sample type, where the columns in the grid will differ for each type (and sometimes within the same type based on other

问题 UPDATE: So pretty much everyone here has told me that I just need to start all over again on how I designed my classes (thank you folks for your excellent answers by the way!). Taking the hint, I started doing extensive reading on the strategy pattern. I want to create behavior classes (or strategy classes) that inherit from an abstract base class or classes. The Candidate class would then have properties w/ the different abstract base class/classes as the Type for the behaviors or strategies

问题 Consider the following classes: public abstract class Token { private List<Token> _Tokens { get; set; } // ReadOnly public is mandatory. How to give protected add-only, index-based access? public ReadOnlyCollection<Token> Tokens { get { return (this._Tokens.AsReadOnly()); } } // AddOnly for derived classes. protected Token AddToken (Token token) { this._Tokens.Add(token); return (token); } } public class ParenthesesToken: Token { // This method is called frequently from public code. public

问题 Something along these lines: interface A { a: number; x: any; } interface B extends A { b: number; } interface C { a: number; b: number; } So the B would be equal to C (omitting field x but still extending A ). Is it possible? If so, how? 回答1: It is impossible to remove an inherited field/method of an interface in TypeScript. But you can overcome this via interfaces reengineering: Extract base interface interface BaseA { a: number; } interface A extends Base A { x: any; } interface B extends

问题 I'm writing a game (space invaders) on an Arduino which is connected to a graphical LCD, and I have a sprite class. This class has attributes such as Player/Alien, a bitmap object, location(x,y), and a how to move function. I want each instance to have a missile and I think this may be done by inheritance and polymorphism, though I'm unsure how -- my streamlined code is below and to give a better idea as to shapes I've included a glyph image. I'd like Missile to derive location(x,y) from the

问题 I was thinking of automatically adding child classes to parent for "chaining" using a metaclass. However, inheriting these attributes from parent classes messes thing up. Is there a nice way to avoid this? class MetaError(type): def __init__(cls, name, bases, attrs): for base in bases: setattr(base, name, cls) super(MetaError, cls).__init__(name, bases, attrs) class BaseError(Exception, object): def __init__(self, message): super(BaseError, self).__init__(message) class HttpError(BaseError):

问题 Given two simple data types, say, restricted strings type1 , type2 , is there a possibility to define type3 describing all strings formed by concatenating one type1 string plus one type2 string? For example, consider <xsd:simpleType name="type1"> <xsd:restriction base="xsd:string"> <xsd:pattern value="[A-Z]"></xsd:pattern> </xsd:restriction> </xsd:simpleType> <xsd:simpleType name="type2"> <xsd:restriction base="xsd:string"> <xsd:pattern value="[0-9]"></xsd:pattern> </xsd:restriction> </xsd

问题 This question already has answers here : C#: interface inheritance getters/setters (4 answers) Closed 3 years ago . I have two interfaces and one implementation: IState , IEditableState and State , in which I have a single integer property called Value . I want to be using IState to get this property and IEditableState to set it. My code looks thusly: interface IState { int Value { get; } } interface IEditableState:IState { int Value { set; } } class State:IEditableState { int Value { get;