Thread: Range-based looping over container of references

Hey guys,

I've got a simple question: Is it possible to create a class that stores (non-const) references to some objects and enables users direct access by using range-based for loops on them?

Code:

class container {
public:
    void add(int& value);
    void remove(int& value);
    ...
};

int main()
{
    container c;
    for (auto& value:c) {
        // `value' should be accessible as type `int&' instead of being a pointer, `std::reference_wrapper<int>' or something like that
    }
}

I think the code shown above provides sufficient explanation of what I want.. Thanks in advance!

Yes, you just need to implement a bunch of iterators.

More specifically, these:
C++ concepts: Container - cppreference.com

Argh, I already was afraid there would be no other way.. Implementing tons of iterators is actually not what I want :/ Thanks anyway!

I think that you will have a problem creating a class that stores references such that they can be added and removed. You can have members of reference type or a reference to a pointer, but not a container of references or a pointer to a reference. However, if you have a container of (smart) pointers, you could implement what manasij7479 mentioned.

Yes, that's what I'm trying to achive:

Code:

class container {
public:
    using iterator=typename std::vector<std::reference_wrapper<argument>>::iterator; // won't work
    using const_iterator=typename std::vector<std::reference_wrapper<argument>>::const_iterator; // won't work
    
    iterator begin() noexcept; // calling `*begin()' would resolve into `std::reference_wrapper<argument>' instead of `argument'
    const_iterator begin() const noexcept;

    iterator end() noexcept; // same as `begin()'
    const_iterator end() const noexcept;
    
private:
    std::vector<std::reference_wrapper<argument>> m_arguments;
};

Thus, one still has to deal with raw pointers, smart pointers or reference wrappers within a range-based for loop:

Code:

container c;
for (auto& object:c) {
    object.get().some_function(); // would be great to use `object.some_function()' instead
}