Re: assignment operator implementation
Frederick Gotham wrote:
I also found an implementation like this:
c& c::operator=(const c& other)
{
if (&other != this)
{
c::~c();
new(this) c(other);
}
return *this;
}
What do you think of it?
peter koch larsen:
That one belongs to the book of horrors. Imagine what happens if the
copy constructor fails.
Ganesh posted:
That's crap. It's both inefficient and unsafe. What would happen if the
copy constructor throws an exception? Definitely not recommended.
I disagree with both of you. The placement new option is efficient:
#include <new>
MyClass &operator=(MyClass const &rhs)
{
if (this != &rhs)
{
this->~MyClass();
::new((void*)this) MyClass(rhs);
}
}
See Sutter "Exceptional C++" for why that's evil.
Consider:
class MyOtherClass : public MyClass
{
public:
MyOtherClass();
MyOtherClass(const MyOtherClass&);
MyOtherClass& operator=(const MyOtherClass& other)
{
MyClass::operator=(other);
some_other_data_ = other.some_other_data_;
}
// other methods redacted for clarity.
private:
int some_other_data_;
}
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