How can I test an NSString for being nil?

Question

Can I simply use

if(myString == nil)

For some reason a string that I know is null, is failing this statement.

Answer 1

You can implicitly check for nil (allocated, but not initialized) with this:

if (!myString) { 
    //do something
}

If myString was assigned from a dictionary or array, you may also wish to check for NSNULL like this:

if ([myString isEqual:[NSNull null]]) {
    //do something
}

Finally (as Sophie Alpert mentioned), you can check for empty strings (an empty value):

if ([myString length] == 0) {
    //do something
}

Often, you may want to consolidate the expressions:

if (!myString || [myString length] == 0) {
    //do something
}

Answer 2

Notice length = 0 doesn't necessary mean it's nil

NSString *test1 = @"";
NSString *test2 = nil;

They are not the same. Although both the length are 0.