I mean, if i have some class like:
class A{
int* pi;
};
*A pa;
when i call delete pa, will pi be deleted?
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It will be if you code it to be. It won't be if you code it not to be. Decide which you want and code that.David Schwartz– David Schwartz2012-02-29 11:43:12 +00:00Commented Feb 29, 2012 at 11:43
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Avoid this with standard library containers or smart pointers as members.stefaanv– stefaanv2012-02-29 11:59:47 +00:00Commented Feb 29, 2012 at 11:59
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No. But note it will call the destructor where you can do clean up of the A instance. If you want to delete pi there then you can do that. BUT you must make sure you correctly own the pointer first. Loop up rule of three.Loki Astari– Loki Astari2012-02-29 15:36:09 +00:00Commented Feb 29, 2012 at 15:36
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3 Answers
You need to define a destructor to delete pi;. In addition you also need to define a copy constructor and assignment operator otherwise when an instance of A is copied two objects will be pointing to the same int, which will be deleted when one of the instances of A is destructed leaving the other instance of A with a dangling pointer.
For example:
class A
{
public:
// Constructor.
A(int a_value) : pi(new int(a_value)) {}
// Destructor.
~A() { delete pi; }
// Copy constructor.
A(const A& a_in): pi(new int(*a_in.pi)) {}
// Assignment operator.
A& operator=(const A& a_in)
{
if (this != &a_in)
{
*pi = *a_in.pi;
}
return *this;
}
private:
int* pi;
};
Comments
You should implement a destructor, ~A(), that takes care of cleaning up A's stuff. Afterwards, calling delete on a pointer of type A will clean-up everything.
1 Comment
Mike Seymour
But always remember that, if you need a destructor, you almost certainly need a copy constructor and copy-assignment operator too, per the Rule of Three
You will need to write a destructor to delete all pointer type members. Something like:
class A
{
int *pi;
public:
~A(){delete pi;}
};
You will need to ensure that your constructor assigns a value to pi( at least a NULL). and like the answer from @hmjd, you will need to implement or hide the copy constructor and assignment operators. Look for the rule of three here: http://en.wikipedia.org/wiki/Rule_of_three_%28C%2B%2B_programming%29
