inheritance

问题 Let's say we have a 2D array, image , eg. 20x20. I would like add a method, called 'imshow' to this object such that whenever I do image.imshow(**kwargs) ), the method imshow will make a call of Matplotlib.pyplot.imshow What is the best way to do this? I was thinking of writing a class with an inheritance from numpy.ndarray, and adding a method 'imshow'. 回答1: Just found the answer (thanks to How can a class that inherits from a NumPy array change its own values?)! class array(np.ndarray): def

问题 Let's say we have package a and package b , both have many classes, all public . Now class Cat from package a wants to extend class Animal from package b , is this inheritance legal? 回答1: ASure, just import the parent class and extend it. package a; import b.Animal; public class Cat extends Animal { } You can skip the import and use the fully qualified class name for Animal as well. But messier. 回答2: Yes. Packages make grouping classes convenient, and non-public and non-private methods and

问题 I have two constructors in two different js files. I want the constructors to have two methods that are the same (same name and functionality) and one method that is called the same but works differently (same name but not the same functionality). There will also be a couple of other properties that are the same in both constructors. The way I have tried to achieve this is by having one of the constructors inherit the other and then declare a new method with the same name as an old one (see

问题 I have a situation where I want to make normal property to be readonly in derived class with default value. I am using keyword new for that purpose in the following way: public abstract class BaseClass { public virtual string SomeInfo { get; set; } } public class DerivedClass1 : BaseClass { public new string SomeInfo => "ChildInfo1"; // C# 6.0 equivalent of { get { return "ChildInfo1"; } } } It works fine, and new DerivedClass1().SomeInfo cannot be assigned to -- it is readonly. I'm aware

问题 Is there a way to define a "member variable" as an "extension object" instead of a static type (without using an interface)? Simply something like this pseudocode: class Foo { bar -> extends Rectangle; constructor(barInstance:IRectangle){ this.bar = barInstance; this.bar.getArea(); //<-- is code completed because interface IRectangle // no type error this.bar.someCustomFunction = function() { } } } instead of class Foo { bar: IRectangle; //or bar:Rectangle; } This way I can add properties not

问题 I'm trying to create a JFrame in one class and adding a JPanel to it in my main class, is this not possible? This is my Main class public class Main { JPanel p; JLabel lbl1; public static void main(String[] args) { new Main(); } Main() { new Window(); JPanel p = new JPanel(); JLabel lbl1 = new JLabel("Hello"); p.add(lbl1); } } And the Window class public class Window extends Main { Window() { JFrame frame = new JFrame(); frame.setSize(400, 400); frame.setDefaultCloseOperation(JFrame.EXIT_ON

问题 I use arrow functions in my classes instead of methods because they allow me to use the "this" keyword, and keep the "this" meaning the class itself, rather than the method. I have an abstract class that defines an empty arrow function that is to be overridden by the child class. Correction, it was originally this: abstract _configureMultiselect(): void; but trying to override that with an arrow function caused this: Class 'CategorySelect' defines instance member function '

问题 I use arrow functions in my classes instead of methods because they allow me to use the "this" keyword, and keep the "this" meaning the class itself, rather than the method. I have an abstract class that defines an empty arrow function that is to be overridden by the child class. Correction, it was originally this: abstract _configureMultiselect(): void; but trying to override that with an arrow function caused this: Class 'CategorySelect' defines instance member function '

问题 I use arrow functions in my classes instead of methods because they allow me to use the "this" keyword, and keep the "this" meaning the class itself, rather than the method. I have an abstract class that defines an empty arrow function that is to be overridden by the child class. Correction, it was originally this: abstract _configureMultiselect(): void; but trying to override that with an arrow function caused this: Class 'CategorySelect' defines instance member function '

问题 I have an abstract base class in C++ and need to create an array to store objects which are subclasses of it. I use pointers to the subclasses since each member of the array needs to be of the same size. Currently I am declaring and initializing my array like this: BaseClass *array[]; ... array = { &SubClass1(...), &SubClass2(...), ... &SubClass3(...) }; This is giving me the following when I try to compile: warning: taking address of temporary error: too many initializers for ‘BaseClass* [0]