c++中的作文

Question

I know the basic idea of composition that the composition has "have" relationship.But when it came to implement the idea of composition something went wrong,Till now i didn't figure out the object and constructor call of another class in the base class. Please help me on this regard.

Answer 1

Composition means that the contained class object does not exist beyond the lifetime of the outer class(which contains it) object.

Online Sample :

#include <iostream>

class MyClass
{
    public:
        MyClass(){std::cout<<"\nMyClass";}
        ~MyClass(){std::cout<<"\n~MyClass";}
};

class MySecClass
{
    MyClass obj;
    public:
        MySecClass(){std::cout<<"\nMySecClass";}
        ~MySecClass(){std::cout<<"\n~MySecClass";}
};

int main()
{
    MySecClass obj;
    return 0;
}

Output:

MyClass
MySecClass
~MySecClass
~MyClass