As mentioned by other here: Interfaces are not necessary in Python. This is because Python has proper multiple inheritance, and also ducktyping, which means that the places where you must have interfaces in Java, you don’t have to have them in Python. That said, there are still several uses for interfaces. Some of them are covered by … Read more
A function is a piece of code that is called by name. It can be passed data to operate on (i.e. the parameters) and can optionally return data (the return value). All data that is passed to a function is explicitly passed. A method is a piece of code that is called by a name that is associated with … Read more
Private members are only accessible within the class defining them. Protected members are accessible in the class that defines them and in classes that inherit from that class. Edit: Both are also accessible by friends of their class, and in the case of protected members, by friends of their derived classes. Edit 2: Use whatever … Read more
They are absolutely different. Inheritance is an “is-a” relationship. Composition is a “has-a”. You do composition by having an instance of another class C as a field of your class, instead of extending C. A good example where composition would’ve been a lot better than inheritance is java.util.Stack, which currently extends java.util.Vector. This is now … Read more
What are you using to compile this? If there’s an undefined reference error, usually it’s because the .o file (which gets created from the .cpp file) doesn’t exist and your compiler/build system is not able to link it. Also, in your card.cpp, the function should be Card::Card() instead of void Card. The Card:: is scoping; … Read more
The differences between a class and a struct in C++ is: struct members and base classes/structs are public by default. class members and base classes/struts are private by default. Both classes and structs can have a mixture of public, protected and private members, can use inheritance and can have member functions. I would recommend you: … Read more
In this code: … the self variable represents the instance of the object itself. Most object-oriented languages pass this as a hidden parameter to the methods defined on an object; Python does not. You have to declare it explicitly. When you create an instance of the A class and call its methods, it will be passed automatically, as in … Read more
A great example illustrating LSP (given by Uncle Bob in a podcast I heard recently) was how sometimes something that sounds right in natural language doesn’t quite work in code. In mathematics, a Square is a Rectangle. Indeed it is a specialization of a rectangle. The “is a” makes you want to model this with inheritance. However if … Read more
The Inversion of Control (IoC) and Dependency Injection (DI) patterns are all about removing dependencies from your code. For example, say your application has a text editor component and you want to provide spell checking. Your standard code would look something like this: What we’ve done here creates a dependency between the TextEditor and the … Read more
The benefits of super() in single-inheritance are minimal — mostly, you don’t have to hard-code the name of the base class into every method that uses its parent methods. However, it’s almost impossible to use multiple-inheritance without super(). This includes common idioms like mixins, interfaces, abstract classes, etc. This extends to code that later extends yours. If somebody … Read more