CODEWITHSUNDEEP
c++c++11
Mircea Ispas
Mircea Ispas

Reputation: 20790

Exposing member variables methods in C++

I have a simple Object-Components design. Something like:

class Object1 : public Object
{
    Component1 _comp1;
    Component2 _comp2;
    ...
    ComponentN _compN;
};

Is it possible to expose as public: methods of Objects1 some methods from ComponentK without creating a method in Object1 that calls internally ComponentK method?

I need a simple way of doing this because it's quite annoying to write a function every time I want to expose some ComponentK method.

Upvotes: 5

Views: 2479

Answers (2)

user12484139
user12484139

Reputation: 11

You can return a pointer to the members; the pointer will be owned by the caller and can be deleted without affecting the class member:

// Example program
#include <iostream>
#include <string>


class Member {
    private:
        int size = 10;
    public:
        int getSize() {
            return size;
        };
};

class MemberContainer {
    private:
        Member member;
    public:
        Member * getMember () {
            return &member;
        };
};

int main()
{
  MemberContainer memberContainer;
  Member * memberPtr = memberContainer.getMember();
  std::cout << memberPtr->getSize() << std::endl;
  memberPtr = nullptr;
  delete memberPtr;
  Member * anotherMemberPtr = memberContainer.getMember();
  std::cout << anotherMemberPtr->getSize() << std::endl;
}

This will output:

10
10

Upvotes: 0

Angew is no longer proud of SO
Angew is no longer proud of SO

Reputation: 171127

Not directly, no. You could use private inheritance to inherit from the components instead of aggregating them (note that private inheritance does not express is-a), and then publish some of their member functions by using. Something like this:

class Object1 : public Object, private Component1, private Component2, ..., private ComponentN
{
public:
  using Component1::function1();
  using Component1::function2();
  ...
  using ComponentN::functionM();
};

I'm not saying it's necessarily the best way to do it, but it's a way.

Upvotes: 14

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