如何确定NSString是否全部大写

Question

How would I go about determining if a string is in all caps or not?

I know you can check each individual character for being part of the upperCase character set, but is there a quicker way?

Answer 1

You could try something like:

if ([[s uppercaseStringWithLocale:[NSLocale currentLocale]] isEqualToString:s])
{
    // ... s is uppercase ...
}
else
{
    // ... s is not all uppercase ...
}

Answer 2

There are a few different ways to interpret your question, and each of these examples just tests your string, without having to create a new copy:

1) You want to make sure that all letters that are in the string are in uppercase (but other characters, like punctuation, numbers, and white space are still allowed). Example:

NSCharacterSet *lowerCaseSet = [NSCharacterSet lowercaseLetterCharacterSet];

if ([myString rangeOfCharacterFromSet:lowerCaseSet].location == NSNotFound)
    NSLog(@"String is in upper case.");
else
    NSLog(@"String has invalid characters.");

2) You want to make sure that all of the characters in the string are uppercase characters (and no other characters are allowed). Example:

NSCharacterSet *invalidCharacterSet = [[NSCharacterSet uppercaseLetterCharacterSet] invertedSet];

if ([myString rangeOfCharacterFromSet:invalidCharacterSet].location == NSNotFound)
    NSLog(@"String has only upper case characters.");
else
    NSLog(@"String has invalid characters.");

3) You want to make sure that all of the characters in the string are uppercase characters or whitespace (and no other characters are allowed). Example:

NSMutableCharacterSet *allowedCharacterSet = [NSMutableCharacterSet uppercaseLetterCharacterSet];
[allowedCharacterSet formUnionWithCharacterSet:[NSCharacterSet whitespaceCharacterSet]];
NSCharacterSet *invalidCharacterSet = [allowedCharacterSet invertedSet];

if ([myString rangeOfCharacterFromSet:invalidCharacterSet].location == NSNotFound)
    NSLog(@"String has only upper case characters and/or white space.");
else
    NSLog(@"String has invalid characters.");

Answer 3

It depends a bit exactly what you're looking for.

If you want to know if the string only contains upper case letters. I'd look for a regular expression match for [AZ]* and compare lengths. I'm not sure how reliable [AZ]* is for non-english alphabets.

If you want to know if there are any lower case characters in the string, but you don't care about punctuation, user1118321's answer is good.

Answer 4

Many good answers here, so let me just chip in a regular expression based one that works with letters from several national alphabets.

Gordon Dove rightly mentioned that a traditional [AZ]* only matches the actual characters in the Latin/English alphabet from A to Z, and wouldn't work with for instance accented characters or other alphabets altogether.

So for the sake of completeness, here is the ICU regex that matches uppercase letters as defined by them: \\p{Lu} (a single uppercase letter).

To test it (with some western European characters, that I could type on my keyboard, the reader should feel free to add others):

NSString *lowercase = @"äbcdéfghìjklmñöpqrstûvwxyzæøå";
NSString *mixedcase = @"ÄbcDÉFGHïjkLmÑÖpqrstÛvwxyzÆøÅ";
NSString *uppercase = @"ÄBCDÉFGHÏJKLMÑÖPQRSTÛVWXYZÆØÅ";

NSArray *cases = @[lowercase, mixedcase, uppercase];

NSString *uppercasePattern = @"\\p{Lu}*"; // Letter, uppercase, zero or more occurrences

NSPredicate *ucPred = [NSPredicate predicateWithFormat:@"self MATCHES %@", uppercasePattern];

NSArray *ucArray = [cases filteredArrayUsingPredicate:ucPred];

If you just need to test a single string, you can use the predicate directly:

if ( [ucPred evaluateWithObject:uppercase] )  {
    NSLog(@"It's uppercase");
}

You don't have to define the pattern string as a separate variable, but I tend to find it enhances readability of the code.