CODEWITHSUNDEEP
c++boostshared-ptrsmart-pointers
user1459961
user1459961

Reputation:

How can I use shared_ptr of boost in this situation?

I have 2 classes, A and B.

In class A, I have a pointer on B called Bptr.

I allocate memory for Bptr in the constructor of A, and I free memory of Bptr in A's destructor.

class B {
//whatever
public:
    B(int,int);
}

class A {
private:
    B * Bptr;
public:
    A();
}

A::A(){
    Bptr = new B(2,5);
}

A::~A(){
    delete Bptr;
}

How can I integrate Boost in my code and use the smart pointer : boost::shared_ptr ? How would my code look like?

Thanks a lot!

Upvotes: 0

Views: 91

Answers (2)

Mike Seymour
Mike Seymour

Reputation: 254461

The first question to ask yourself: why do you want to dynamically allocate the object in the first place? Can you just replace the pointer with a member of type B?

Assuming there is a good reason, then why shared_ptr (rather than scoped_ptr or, in modern C++, unique_ptr)? Why do you need shared ownership?

Once you've answered these questions, and determined that shared ownership is the right solution, just replace B* with a shared pointer, initialise it in the constructor, and get rid of the redundant destructor (assuming it's not needed for anything else).

class A {
private:
    boost::shared_ptr<B> Bptr;
public:
    A() : Bptr(boost::make_shared<B>(2,5)) {}
};

You could simply initialise it with a pointer, Bptr(new B(2,5)), but using make_shared makes more efficient use of memory and (in more complicated situations than this) makes it easier to ensure exception safety.

Upvotes: 1

Nicu Stiurca
Nicu Stiurca

Reputation: 8677

class B {
//whatever
public:
    B(int,int);
}

class A {
private:
    boost::shared_ptr<B> Bptr;
public:
    A();
}

A::A(){
    Bptr = boost::make_shared<B>(2,5);
}

A::~A(){
  // Bptr automatically deleted if this is the only boost::shared_ptr pointing to it
}

Although you could simply use new B(2,5) instead of boost::make_shared<B>, the latter is exception-safe.

Upvotes: 0

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