Reputation: 3973
I have the following sample code, and the copy assignment is doing something I don't want - it's first constructing the new samp(6), then copying it to z, then destroying the new samp(6) it built. Is there a way to change the constructors such that = acts like a pointer, destroying the originally constructed samp(5) and replacing it with the new samp(6), calling the destructor on samp(5), rather than samp(6)?
#include <iostream>
class samp
{
public:
samp(int a)
{
m_a = a;
std::cout << "cons" <<m_a << std::endl;
}
int m_a;
samp(const samp& other)
{
std::cout << "copy" << m_a << std::endl;
m_a = other.m_a;
}
samp& operator= (const samp& other)
{
std::cout << "assg" << m_a << std::endl;
samp* z =new samp(other.m_a);
return *z;
}
~samp()
{
std::cout << "dest" <<m_a<< std::endl;
}
};
int main()
{
samp z(5);
z = samp(6);
std::cout << z.m_a << std::endl;
return 0;
}
Upvotes: 0
Views: 73
Reputation: 141613
Maybe pointer semantics is what you want:
#include <memory>
// ...
auto z = std::make_unique<samp>(5);
z = std::make_unique<samp>(6); // dest5
std::cout << z->m_a << '\n'; // 6
Although if you are coming to C++ from a language where object names are object references, it may be better to get used to C++ value semantics instead of trying to replicate object references :)
Upvotes: 1
Reputation: 372
operator=
is a member of your object so the this
pointer is available. Also, assignment means the target of the assignment should change. Your version is creating a new object, but leaving the target alone. See if this does what you want:
samp& operator= (const samp& other)
{
m_a = other.m_a;
return *this;
}
Upvotes: 0