CODEWITHSUNDEEP
c++class
xinthose
xinthose

Reputation: 3820

How to call class destructor / constructor

Say I have two classes like so:

controller.hpp (included by controller.cpp)

#include "testing.hpp"
class controller
{
    public:
        testing _testing;  // call constructor
}

testing.hpp

class testing
{
    public:
        testing();
        ~testing();
}

How do I call the destructor of testing and re-construct it from controller.cpp? Thank you.

Upvotes: 0

Views: 479

Answers (3)

Allison Lock
Allison Lock

Reputation: 2383

In your code a controller owns a testing. The implication to anyone reading the code is that it is the same testing for the lifetime of the controller. This is certainly also how C++ see it - it will construct the testing during construction of a controller and destroy the testing when the controller is destroyed.

Two possible solutions:

  1. Instead of trying to replace testing, reset it. This is what @LogicStuff was talking about in his comment on your question. _testing = testing(); constructs a new testing and then copies its state to the existing instance, making the exisiting instance look like a new one. You could (should?) make this explicit by giving testing a Reset method (whose implementation should typically be that assignment *this = testing(); rather than a hand-coded resetting of each member variable.) - Do this only if resetting a testing makes business sense.
  2. If resetting testing doesn't make sense on a business level, and you are in fact wanting to replace it, then have controller own a std::unique_ptr<testing> instead. Then you can reset or swap a newly constructed instance in whenever you need to and still be sure that destructors will be called automatically.

Upvotes: 1

Paul Kelly
Paul Kelly

Reputation: 4019

You usually don't explicitly call the destructor. It is call automatically when the object is destroyed. When an object is created on the stack, the destructor is called automatically when the object goes out of scope. When an object is created on the heap (by new'ing it), the destructor is called automatically when delete is called on the object.

Upvotes: 2

SergeyA
SergeyA

Reputation: 62553

I think, you totally misunderstand the idea of default constructors. The main idea is that you almost never call default constructor explicitly (absent placement new). Ditto for destructors. So in your case, testing constructor will be called automatically whenever controller object is created, and it it's destructor will be called whenever controller object is destroyed.

Upvotes: 2

Related Questions