Mixins may contain state, (traditional) traits don’t. Mixins use “implicit conflict resolution”, traits use “explicit conflict resolution” Mixins depends on linearization, traits are flattened. Lecture about traits ad 1. In mixins you can define instance variables. Traits do not allow this. The state must be provided by the composing class (=class using the traits) ad … Read more
There is always just one constructor call, and always of the actual, concrete class that you instantiate. It is your responsibility to endow each derived class with a constructor which calls the base classes’ constructors if and as necessary, as you did in B‘s constructor. Update: Sorry for missing your main point! Thanks to ildjarn. … Read more
The answer to the duplicate operation is: To solve multiple inheritance issue a class implementing two interfaces providing a default implementation for the same method name and signature must provide an implementation of the method. [Full Article] My answer to your question is: Yes, it is a form of multiple inheritance, because you can inherit … Read more
Surprisingly, the test that prevents instantiating abstract classes happens in object.__new__, rather than anything defined by the abc module itself: static PyObject * object_new(PyTypeObject *type, PyObject *args, PyObject *kwds) { … if (type->tp_flags & Py_TPFLAGS_IS_ABSTRACT) { … PyErr_Format(PyExc_TypeError, “Can’t instantiate abstract class %s ” “with abstract methods %U”, type->tp_name, joined); (Almost?) all built-in types that … Read more
Most uses of full scale Multiple inheritance are for mixins. As an example: class DraggableWindow : Window, Draggable { } class SkinnableWindow : Window, Skinnable { } class DraggableSkinnableWindow : Window, Draggable, Skinnable { } etc… In most cases, it’s best to use multiple inheritance to do strictly interface inheritance. class DraggableWindow : Window, IDraggable … Read more
super() is not broken — it just should not be considered the standard way of calling a method of the base class. This did not change with Python 3.x. The only thing that changed is that you don’t need to pass the arguments self, cls in the standard case that self is the first parameter … Read more
Virtual bases are very different from ordinary bases. Remember that “virtual” means “determined at runtime” — thus the entire base subobject must be determined at runtime. Imagine that you are getting a B & x reference, and you are tasked to find the A::a member. If the inheritance were real, then B has a superclass … Read more
A practical example: class A {}; class B : public A {}; class C : public A {}; class D : public B, public C {}; Notice how class D inherits from both B & C. But both B & C inherit from A. That will result in 2 copies of the class A being … Read more
a.base1::start(); a.base2::start(); or if you want to use one specifically class derived:public base1,public base2 { public: using base1::start; };
Sorry, you cannot inherit from multiple classes. You may use interfaces or a combination of one class and interface(s), where interface(s) should follow the class name in the signature. interface A { } interface B { } class Base { } class AnotherClass { } Possible ways to inherit: class SomeClass : A, B { … Read more