> Il giorno 29 giu 2017, alle ore 03:18, Ben Cohen via swift-evolution
> <[email protected]> ha scritto:
>
> Finally, there’s a woolier justification: there’s an often-touted
> misconception out there that force unwraps are bad, that they were only
> created to accommodate legacy apps, and that force-unwrapping is always bad
> and you should never do it. This isn’t true – there are many good reasons to
> use force unwrap (though if you reaching for it constantly it’s a bad sign).
> Force-unwrapping is often better than just whacking in a default value or
> optional chaining when the presence of nil would indicate a serious failure.
> Introduction of the `!!` operator could help endorse/encourage the use of
> “thoughtful” force-unwrapping, which often comes with a comment of the
> reasoning why it’s safe (of why the array can’t be empty at this point, not
> just that it is empty). And if you’re going to write a comment, why not make
> that comment useful for debugging at the same time.
>
If one could still just "!" I'm not sure that the "!!" would really encourage a
more thoughtful force unwrapping. Almost every crash related to a force unwrap
that I see from Swift beginners is 100% due to the fact that adding and
exclamation point makes the code compile, so they add it.
Also, I strongly disagree with your statement that the idea that force-unwraps
are bad is a misconception: if something is Optional, there's a reason why it
is, otherwise it would not be Optional at all, and that's the reason why
Optional exists in Swift and represents a substantial technological advancement
over Objective-C. Using an Optional means that we are actually adding a
thoughtful information to an instance: it could be there, or it could not, and
that's perfectly fine. Crashing an app in production for a force-unwrap results
in the poorest user experience ever, and it should never happen.
I feel compelled to link another article, where Soroush Khanlou shows that
sometimes the bare semantics of an Optional (that is, something is there or
not) is not enough: http://khanlou.com/2017/03/that-one-optional-property/
<http://khanlou.com/2017/03/that-one-optional-property/>
I also disagree with the idea that the "?? fatalError()" alternative suffers
from cognitive dissonance, for the following reasons:
- on the right of the "??" operator there could be both an Optional or a
non-Optional, which would result in a different type for the resulting instance;
- fatalError() by itself is an operation that changes the meaning of a
function, making it non-total, and its very name conveys a clear meaning to a
person that reads the code, thus it really doesn't seem to me that "??
fatalError()" could be misinterpreted;
Anyway, it would be interesting to consider "!! message" as an alternative to
"!", thus forcing the user to at least do extra effort: that could discourage a
light use of !.
Elviro
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