CODEWITHSUNDEEP
c++templates
RomaValcer
RomaValcer

Reputation: 2956

No matching constructor for iterator

template<class T>
class Vector {
    size_t size;
    size_t allocated;
    T *array;
public:
    Vector() {...};
    Vector(size_t constr_size) {...};
    Vector(const Vector &source) {...};
    ~Vector() {
        delete array;
    };

   /*omitted methods*/

    class iterator : public std::iterator<std::input_iterator_tag, int> {
            Vector<T> *vector;
            size_t position;

        public:
            iterator(Vector<T> *vector_, size_t idx) {
                vector = vector_;
                position = idx;
            };

            iterator(iterator &it) {
                vector = it.vector;
                position = it.position;
            };

            /*more omitted methods*/
    };
    Vector<T>::iterator begin() {
        return Vector<T>::iterator(this, 0);
    };
    Vector<T>::iterator end() {
        return Vector<T>::iterator(this, size);
    };
};

When I try to create a Vector and work with iterators I get an error No matching constructor for initialization of 'Vector::iterator'. Why does it happen? Seems like all required fields are defined, yet somehow I get an error.

Upvotes: 1

Views: 620

Answers (1)

TartanLlama
TartanLlama

Reputation: 65620

Vector<T>::iterator begin() {
    return Vector<T>::iterator(this, 0);
};

Since you return by value here, the copy constructor for iterator will be called. That looks like this:

iterator(iterator &it);

Note that you are trying to copy-construct using a temporary (Vector<T>::iterator(this,0)), but the copy constructor takes its argument by non-const reference. You can't bind a temporary to a non-const reference, hence the error.

The simple fix is to make the copy constructor take a const reference:

iterator(const iterator &it);

Upvotes: 5

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