What's the difference between true and YES in iOS Objective-C

Question

I have read that the two are the same, but my code does not work if I use true/false instead of YES/NO. For example if I do

BOOL matchFound=false;
//...
//logic to change value of matchFound to `true` goes here
//...
if(!matchFound) NSLog(@"I did not find a match");

The above does not work properly. But if I change to using YES/NO, it works. Why is that?

I'm unable to reproduce. But I would agree with Bas that this is a duplicate (though a good question) so that's moot. — Tommy, Jan 21 '15 at 17:52

score 7 · Accepted Answer · answered Jan 21 '15 at 17:53

7

That is because YES/NO are not actually boolean values, but instead they are signed char types. This is a relic from the old C days where there was no boolean type.

The article linked below will explain in more details, but in general you should always use YES/NO when dealing with BOOL values in iOS.

http://iosdevelopertips.com/objective-c/of-bool-and-yes.html

Hope this helps!

answered Jan 21 '15 at 17:53

miken.mkndev

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... with the caveat that in the 64-bit runtime `BOOL` is explicitly a typedef for C99's `bool`. – Tommy Jan 21 '15 at 17:55
Link is no longer working... – damcify Jul 18 '23 at 07:13

What's the difference between true and YES in iOS Objective-C

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