在类定义中使用删除的副本构造函数和初始化程序列表重载调用成员构造函数

Question

struct Foo
{
    Foo(const Foo&) = delete;
    Foo(int a, int b);
    Foo(std::initializer_list<int>);    
};

struct Bar
{
    Foo f = Foo(1, 2);
    // Foo f = {1, 2} - calls the initializer_list overload
};

How to initialize Foo with two ints if the copy constructor is deleted?

Answer 1

In order for that initialization to work, the type in question has to be MoveConstructible ^* . In your particular case, providing a move constructor would satisfy this requirement:

Foo(Foo&&) = default;

If this is not an option, you could initialize the member in a default constructor, and use it as a delegating constructor in other constructors.

struct Bar
{
    Bar() : f(1, 2) {}
    Bar(const FooBar&) : Bar() {}
    Bar(double x) : Bar() {}
    Foo f;
};

---

^{* This does not mean a copy will be made. T t = T() is an easy candidate for copy elision. However, a viable constructor must be accessible.}