You have to read the API carefully for this methods. Sometimes you can get confused very easily. It is either: if (B.class.isInstance(view)) API says: Determines if the specified Object (the parameter) is assignment-compatible with the object represented by this Class (The class object you are calling the method at) or: if (B.class.isAssignableFrom(view.getClass())) API says: Determines … Read more
As others have mentioned, the sole reason for defining __slots__ is to save some memory, when you have simple objects with a predefined set of attributes and don’t want each to carry around a dictionary. This is meaningful only for classes of which you plan to have many instances, of course. The savings may not … Read more
Don’t make the method static. The issue is that when you invoke getClass() you are calling the method in the super class – static methods are not inherited. In addition, you are basically name-shadowing Object.getClass(), which is confusing. If you need to log the classname within the superclass, use return this.getClass().getName(); This will return “Entity” … Read more
You never need just super(); That’s what will be there if you don’t specify anything else. You only need to specify the constructor to call if: You want to call a superclass constructor which has parameters You want to chain to another constructor in the same class instead of the superclass constructor You claim that: … Read more
class Base { public: virtual ~Base() {} }; class D1: public Base {}; class D2: public Base {}; int main(int argc,char* argv[]); { D1 d1; D2 d2; Base* x = (argc > 2)?&d1:&d2; if (dynamic_cast<D2*>(x) == nullptr) { std::cout << “NOT A D2” << std::endl; } if (dynamic_cast<D1*>(x) == nullptr) { std::cout << “NOT … Read more
PEP 487 sets out to take two common metaclass usecases and make them more accessible without having to understand all the ins and outs of metaclasses. The two new features, __init_subclass__ and __set_name__ are otherwise independent, they don’t rely on one another. __init_subclass__ is just a hook method. You can use it for anything you … Read more
Are you looking for: Super.class.isAssignableFrom(Sub.class)
There are no abstract classes in Swift (just like Objective-C). Your best bet is going to be to use a Protocol, which is like a Java Interface. With Swift 2.0, you can then add method implementations and calculated property implementations using protocol extensions. Your only restrictions are that you can’t provide member variables or constants … Read more
The crucial distinction between Python’s __init__ and those other languages constructors is that __init__ is not a constructor: it’s an initializer (the actual constructor (if any, but, see later;-) is __new__ and works completely differently again). While constructing all superclasses (and, no doubt, doing so “before” you continue constructing downwards) is obviously part of saying … Read more
When you specify cls: A, you’re saying that cls expects an instance of type A. The type hint to specify cls as a class object for the type A (or its subtypes) uses typing.Type. from typing import Type def process_any_subclass_type_of_A(cls: Type[A]): pass From The type of class objects : Sometimes you want to talk about … Read more