C++ 对 class 使用 std::fill 并删除分配运算符

Question

Suppose I have a range of objects

class X {
public:
    X()
        : X(0) {
    }
    X(size_t num)
        : x_(num) {
    }
    X(const X& other) = delete;
    X& operator=(const X& other) = delete;
    X(X&& other) {
        x_ = exchange(other.x_, 0);
    }
    X& operator=(X&& other) {
        x_ = exchange(other.x_, 0);
        return *this;
    }
    size_t GetX() const {
        return x_;
    }

private:
    size_t x_;
};

With this in mind I can't use std::fill as operator= is deleted. What is the right way to fill the range for this kind of object?

Answer 1

Source object of std::fill is const . const object cannot be used as source of move operation.

You can add helper class with conversion operator to X , every time when *first = value; (look at possible implementation of std::fill ) is called, temporary of X is returned and move operation is performed:

template<size_t N>
struct Helper {
    X MakeTemp() const { return X(N); }
    operator X () const { return MakeTemp(); }
};

int main(){
    std::vector<X> v;
    v.resize(10);
    std::fill(v.begin(), v.end(),Helper<10>{});

Demo