how to assign multiple values into a struct at once?

Question

I can do this on initialization for a struct Foo:

Foo foo =  {bunch, of, things, initialized};

but, I can\'t do this:

Foo f         


        

Answer 1

In C++11 you can perform multiple assignment with "tie" (declared in the tuple header)

struct foo {
    int a, b, c;
} f;

std::tie(f.a, f.b, f.c) = std::make_tuple(1, 2, 3);

If your right hand expression is of fixed size and you only need to get some of the elements, you can use the ignore placeholder with tie

std::tie(std::ignore, f.b, std::ignore) = some_tuple; // only f.b modified

If you find the syntax std::tie(f.a, f.b, f.c) too code cluttering you could have a member function returning that tuple of references

struct foo {
    int a, b, c;
    auto members() -> decltype(std::tie(a, b, c)) {
        return std::tie(a, b, c);
    }
} f;

f.members() = std::make_tuple(1, 2, 3);

All this ofcourse assuming that overloading the assignment operator is not an option because your struct is not constructible by such sequence of values, in which case you could say

f = foo(1, 2, 3);