返回结构或错误的惯用方式是什么？

Question

I have a function that returns either a Card, which is a struct type, or an error.

The problem is, how can I return from the function when an error occurs ? nil is not valid for structs and I don't have a valid zero value for my Card type.

func canFail() (card Card, err error) {
    // return nil, errors.New("Not yet implemented"); // Fails
    return Card{Ace, Spades}, errors.New("not yet implemented"); // Works, but very ugly
}

The only workaround I found is to use a *Card rather than a Card, a make it either nil when there is an error or make it point an actual Card when no error happens, but that's quite clumsy.

func canFail() (card *Card, err error) {
    return nil, errors.New("not yet implemented");
}

Is there a better way ?

EDIT : I found another way, but don't know if this is idiomatic or even good style.

func canFail() (card Card, err error) {
    return card, errors.New("not yet implemented")
}

Since card is a named return value, I can use it without initializing it. It is zeroed in its own way, I don't really care since the calling function is not supposed to use this value.

Answer 1

func canFail() (card Card, err error) {
    return card, errors.New("not yet implemented")
}

I think this, your third exampe, is fine too. The understood rule is that when a function returns an error, other return values cannot be relied upon to have meaningful values unless documentation clearly explains otherwise. So returning a perhaps meaningless struct value here is fine.