I'm trying to understand how this type of function works and how you would use it.
I assume there's some class we'll call it test.
class Test {
}
I saw this type of function in a header file and I'm trying to figure out what it does. And how to use it properly.
Test& testFunction();
Appreciate the help.
What's in front of the function name is the type that the function will return. In this case, testFunction is returning a Test object. The & in this case (reference) means that it will return a Test-reference. This is important if you wish to modify the returned object when you call the function. Or use it in some way not possible with "return-by-value".
Your code doesn't tell us much about what you're going to be doing with the return value, but here is a good example that's used quite commonly:
Test & T::f() {
// do something
return *this;
}
*this here is the actual object on which its method .f is being called. What's special here is that since we are returning a reference, we can chain calls while maintaining the original object. *this will be the same *this every time. With return-by-value we aren't able to do this. For example:
Test & T::f() {
this->x++;
return *this;
}
int main() {
Test t;
t.x = 5;
t.f().f();
std::cout << t.x; // 7 as we expect
}
Test T::f() { ... } // notice the omission of &
int main() {
Test t;
t.x = 5;
t.f().f();
std::cout << t.x; // 6
}
t is changed only once because the object is lost on the next call.
