Question

My particular case involves a custom iterator, but this question is a general one. I'm unsure how to write the return type for this postfix increment method:

template<typename T>
struct MyIterator {
    size_t loc;

    MyIterator operator++(int) {
        MyIterator temp(*this);
        ++loc;
        return temp;
    }
};

This compiles, but so does this:

template<typename T>
struct MyIterator {

    size_t loc;

    MyIterator<T> operator++(int) {
        MyIterator<T> temp(*this);
        ++loc;
        return temp;
    }
};

The two other configurations also work fine (i.e. putting the <T> on only one of the instances of MyIterator). Is there a "correct" way to write this? Does it matter?

Answer 1

Is there a "correct" way to write this?

Both names are correct. However, using the injected class name is simpler and preferable, especially if there are more than one template parameters. Imagine you have:

template <typename T1, typename T2, typename T3> class MyClass { ... };

Inside the class template, it is preferable to use MyClass than MyClass<T1, T2, T3>.

Does it matter?

No.

Since you are inside the scope of the class, the name lookup will find what you expect. This has to do with injected class name, and I suggest you to read more about it here: Why is there an injected class name?

Since c++14, another correct way to do it is auto with no trailing return type, as skypjack mentioned.

Correct signature for template class method that returns its own type

1 个答案: