On Apr 24, 2014, at 5:45 PM, Quincey Morris
<quinceymor...@rivergatesoftware.com> wrote:
> On Apr 24, 2014, at 14:21 , Andy Lee <ag...@mac.com> wrote:
>
>> I still don't see how
>>
>> foo = [@"Something" fallbackIfNil:foo];
>>
>> has any advantage over
>>
>> foo = foo ?: @"Something";
>
> I don’t see how the latter has any advantage over your earlier suggestion
> [more or less]:
>
> if (!foo)
> foo = @“Something”;
>
> Admittedly, it takes two lines instead of one.
Well, I'd use braces in the latter case, and I put opening braces on their own
line, so for me it'd be four vs. one. :) But I don't have an objection to the
"long form".
Because "foo" appears twice, you could conceivably change one and forget to
change the other, but that's true of the ?: version too, which is another
argument for a ?:= operator.
Occasionally when there's a repeating pattern I think it's clearer when things
fit on one line, because successive lines make the pattern easier to spot.
What I mean is something like
foo = foo ?: [UserPrefs fooValue];
foo = foo ?: [GlobalSettings fooValue];
foo = foo ?: @"LastResort";
Not that I've done it, but this can even be written as
foo = foo ?: [UserPrefs fooValue]
?: [GlobalSettings fooValue]
?: @"LastResort;
> Is there *any* confusion over the “if” version?
That's an excellent point, and I'm always happy to type a little more to make
things clearer. At the same time, I think reasonable people can differ over
which is preferable. It might just be a matter of acclimation. As a matter of
program logic, binary ?: should be no more confusing than the fact that && and
|| are short-circuiting operators. On the other hand, sometimes splitting a
boolean calculation into separate statements is clearer than using && and/or
||, so your point applies as well.
Consider how unsettling people find it that Objective-C allows and even expects
messages to nil. That is, we routinely say
[obj doSomething];
instead of
if (obj)
{
[obj doSomething];
}
After a while, we get used to the Objective-C way and don't have to calculate
in our heads every time, "Let's see, if obj is nil, this will return zero, and
that's okay because..." Maybe the same could happen with ?:.
--Andy
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