You could use this: A.h #include <B.h> #ifndef A_H #define A_H class A { public: B b1; int m_a; }; #endif // A_H B.h #ifndef B_H #define B_H class A; class B { public: int f(A &a); }; #include <A.h> inline int B::f(A &a) { return a.m_a; } #endif // B_H main.cpp #include <iostream> #include … Read more
A proper forward declaration is simply: class Level; Note the lack of curly braces. This tells the compiler that there’s a class named Level, but nothing about the contents of it. You can then use pointers (Level *) and references (Level &) to this undefined class freely. Note that you cannot directly instantiate Level since … Read more
Everything is dynamic in Python – even the class declarations. There’s nothing to stop you modifying the contents of a class after the initial declaration: class A: pass class B: a = A() A.b = B() NB: If you’re not that familiar with Python, the pass keyword simply allows you to say ‘nothing here’ – … Read more
Importing a class is not inheritance. Objective-C doesn’t allow circular inheritance, but it does allow circular dependencies. What you would do is declare the classes in each other’s headers with the @class directive, and have each class’s implementation file import the other one’s header. To wit: ClassA.h @class ClassB; @interface ClassA : NSObject { ClassB … Read more
The error Accessing non-existent property ‘MongoError’ of > module exports inside circular dependency is caused by a bug in mongodb 3.6.4 It’s already reported here Back to version 3.6.3 works for me: npm uninstall mongodb –save Install version 3.6.3 npm i [email protected]
You can’t forward declare members. Instead, bar.cpp should #include both foo.h and bar.h. Problem solved. In general, if you use the sequence: Forward declare all class types Define all class types Bodies of class members everything will be fine.
Here is what happens in chronological order: Class B contains the main-method so it is loaded by the class loader. Initialization of B references A, so class A is loaded. A has a static variable X initialized to B.Y + 1. The initialization of B.Y hasn’t been executed yet, so B.Y evaluates to 0, and … Read more
You need to take a 2-pass, or multi-pass approach: Languages like Java require a multi-pass compiler since the definition of x would not be required to come before the use: public class Example { public static void main(String [] args) { assert(x==0); x++; assert(x==1); } static int x=0; } There are various approaches, for example … Read more
Reason [1] Faster compile times Not in my projects: source files (CPP) only include the headers (HPP) they need. So when I need to recompile only one CPP because of a tiny change, I have ten times the same number of files that are not recompiled. Perhaps you should break down your project in more … Read more
If you do import foo (inside bar.py) and import bar (inside foo.py), it will work fine. By the time anything actually runs, both modules will be fully loaded and will have references to each other. The problem is when instead you do from foo import abc (inside bar.py) and from bar import xyz (inside foo.py). … Read more