Assign empty string only if variable is nil (ternary operator)

Question

I'm trying to achieve the equivalent of the following C# code:

someStringValue = someStringValue ?? string.Empty;

Where if someStringValue is null, a value of string.Empty (the empty string: "") will be assigned. How do I achieve this in Objective-C? Is my only option:

if(!someStringValue)
   someStringValue = @"";

Solution thanks to @Dave DeLong:

someStringValue = someStringValue ?: @"";

I feel that the `if` version is much more simple and readable in Obj-C. — Sulthan, Apr 23 '14 at 12:53

Eric · Accepted Answer · 2013-01-05T18:35:10.140

31

Simple, using ternary operator.

someStringValue = someStringValue ? someStringValue : @"";

Or if you want a macro, you can do that too.

#if !defined(StringOrEmpty)
    #define StringOrEmpty(A)  ({ __typeof__(A) __a = (A); __a ? __a : @""; })
#endif

Sample usage:

someStringValue = StringOrEmpty(someStringValue);

edited Jan 05 '13 at 18:35

answered Jan 05 '13 at 18:25

Eric

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... or even just `someStringValue = someStringValue ?: @"";` – Dave DeLong Jan 05 '13 at 18:35
Thank you, Eric. This is what I was hoping for. @Dave DeLong, thank you as well for streamlining it, I ultimately went with your implementation. – alan Jan 05 '13 at 18:39
1

@DaveDeLong My experience was JavaScript has taught me to avoid apocryphal operators. Even if I know what it is, my teammates probably won't and I'd rather it be immediately obvious. That having been said, +1 for the awesome tip. I had been missing the old `a = b || c` notation and that's just what I've been looking for. – Eric Jan 05 '13 at 18:46

score 0 · Answer 2 · answered Jan 05 '13 at 18:28

0

If someStringValue is a class variable, you could add this code to your .m file that owns the string

- (void)setSomeStringValue:(NSString *)newSomeStringValue
{
   if (!newSomeStringValue) newSomeStringValue = @"";
   _someStringValue = newSomeStringValue;
}

answered Jan 05 '13 at 18:28

Undo

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I thing is more clean override getter, not setter. – skywinder Jan 14 '16 at 07:45

Assign empty string only if variable is nil (ternary operator)

2 Answers2