iPhone - Comparing a nil NSString with another valued NSString returns NSOrderedSame

Question

I'm testing a string with an other, and I notice that if the first string is nil, the return value equals NSOrderedSame (valued to 0).

if([oneString compare:otherString] == NSOrderedSame) returns YES if oneString is nil.

So I should test if(oneString != nil && [oneString compare:otherString] == NSOrderedSame)

I guess I should also test otherString in the condition, and make a special case if I want that [nil compare:nil] returns NSOrderedSame.

Is there a more convenient way to compare string without having to do such tests and to really test if both strings are the same ?

Answer 1

You can try

[someString isEqualToString:@"someOtherString"];

Or for case insensitive:

[[someString lowerCaseString] isEqualToString:[otherString lowerCaseString]];

Answer 2

I would use the approach @seretur suggests unless you are worried about case. In that case, I'd use caseInsensitiveCompare: which is similar to the compare: method you are currently using.

You can also simplify that if statement like so:

if (oneString && [oneString caseInsensitiveCompare:otherString] == NSOrderedSame) { ...

Answer 3

According to the documentation, the string must not be nil. If it is, it can result in quirky behavior.

Answer 4

It is absolute legal to send something to nitl. But by definition it will always return nil. and nil itself actually is 0.

If we now look at NSComparisonResult, NSOrderedSame is 0 too.

enum {
   NSOrderedAscending = -1,
   NSOrderedSame,
   NSOrderedDescending
};
typedef NSInteger NSComparisonResult;