If you don’t want to define a function before it’s used, and defining it afterwards is impossible, what about defining it in some other module? Technically you still define it first, but it’s clean. You could create a recursion like the following: Python’s functions are anonymous just like values are anonymous, yet they can be … Read more
If you will place your definitions in this order then the code will be compiled The definition of function doSomething requires the complete definition of class Ball because it access its data member. In your code example module Player.cpp has no access to the definition of class Ball so the compiler issues an error.
In order to declare a variable of any type, template or not, the entire definition of that type must be available. You cannot forward-declare a template, and then start using it as if it were defined. All you can do at that point is declaring a pointer to an object of a type based on … Read more
Move doSomething definition outside of its class declaration and after B and also make add accessible to A by public-ing it or friend-ing it.
Why forward-declare is necessary in C++ The compiler wants to ensure you haven’t made spelling mistakes or passed the wrong number of arguments to the function. So, it insists that it first sees a declaration of ‘add’ (or any other types, classes, or functions) before it is used. This really just allows the compiler to … Read more
If you will place your definitions in this order then the code will be compiled The definition of function doSomething requires the complete definition of class Ball because it access its data member. In your code example module Player.cpp has no access to the definition of class Ball so the compiler issues an error.