How does shared_ptr work in if condition

Question

In C++, I can write something like:

shared_ptr a_sp = someFunctionReturningSharedPtr();
if (a_sp) {
    cout << a_sp->someData << end         


        

Answer 1

shared_ptr has operator bool(), which returns true if it is not empty.

For example, this is Microsoft implementation of shared_ptr::operator bool(): http://msdn.microsoft.com/en-us/library/bb982901.aspx

shared_ptr::operator boolean-type - Tests if an owned resource exists.