Question

I’m having some trouble keeping objects in a vector, and I think I need to do something with the operators.

std::vector<Foo> vec;
Foo a = Foo();
vec.push_back(a);

...

if(std::find(vec.begin(), vec.end(), a) < vec.end()) {
    // Found
} else {
    // Not found
}

Foo needs operator== to compile, I do this

bool Foo::operator==(const Foo& rhs) {
    return this == &rhs;
}

But from what I understand, vec.push_back, is going to make a copy of the Foo object, so my == will return false.

Hence, whenever I get to the searching, it is never found.

What’s the right thing to do here? I’m hoping to avoid switching to a vector of pointers.

Answer 1

Change the implementation of Foo::operator== to compare the member variables of Foo for equality instead of checking identity. For example:

bool Foo::operator==(const Foo& rhs) const {
    return get_a() == rhs.get_a()
        && get_b() == rhs.get_b(); // and so on
}

Note that this can also be a const function since it should not modify any member variables and should be usable on const instances of Foo.