Why can’t I store a value and a reference to that value in the same struct?

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I have a value and I want to store that value and a reference to
something inside that value in my own type:

struct Thing {
    count: u32,
}

struct Combined<'a>(Thing, &'a u32);

fn make_combined<'a>() -> Combined<'a> {
    let thing = Thing { count: 42 };

    Combined(thing, &thing.count)
}

Sometimes, I have a value and I want to store that value and a reference to
that value in the same structure:

struct Combined<'a>(Thing, &'a Thing);

fn make_combined<'a>() -> Combined<'a> {
    let thing = Thing::new();

    Combined(thing, &thing)
}

Sometimes, I’m not even taking a reference of the value and I get the
same error:

struct Combined<'a>(Parent, Child<'a>);

fn make_combined<'a>() -> Combined<'a> {
    let parent = Parent::new();
    let child = parent.child();

    Combined(parent, child)
}

In each of these cases, I get an error that one of the values “does
not live long enough”. What does this error mean?

3 Answers
3

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