Easy way to set a single character of an NSString to uppercase

Question

I would like to change the first character of an NSString to uppercase. Unfortunately, - (NSString *)capitalizedString converts the first letter of every word to uppercase. Is there an easy way to convert just a single character to uppercase?

I'm currently using:

NSRange firstCharRange = NSMakeRange(0,1);
NSString* firstCharacter = [dateString substringWithRange:firstCharRange];
NSString* uppercaseFirstChar = [firstCharacter originalString];
NSMutableString* capitalisedSentence = [originalString mutableCopy];
[capitalisedSentence replaceCharactersInRange:firstCharRange withString:uppercaseFirstChar];

Which seems a little convoluted but at least makes no assumptions about the encoding of the underlying unicode string.

Solution 1

Since NSString is immutable, what you have seems to be a good way to do what you want to do. The implementations of (NSString*)uppercaseString and similar methods probably look very much like what you've written, as they return a new NSString instead of modifying the one you sent the message to.

Solution 2

Very similar approach to what you have but a little more condense:

 NSString *capitalisedSentence = 
    [dateString stringByReplacingCharactersInRange:NSMakeRange(0,1)  
    withString:[[dateString  substringToIndex:1] capitalizedString]];

Solution 3

Aiming for maximum readability, make a category on NSString and give it this function:

NSString *capitalizeFirstLetter(NSString *string) {
    NSString *firstCapital = [string substringToIndex:1].capitalizedString;
    return [string stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:firstCapital];
}

Then in your code where you want it:

NSString *capitalizedSentence = capitalizeFirstLetter(dateString);

This kind of code rarely belongs in the spot where you need it and should generally be factored away into a utility class or a category to improve legibility.

Solution 4

I had a similar requirement, but it was for characters within the string. This assuming i is your index to the character you want to uppercase this worked for me:

curword = [curword stringByReplacingCharactersInRange:NSMakeRange(i,1) 
           withString:[[curword substringWithRange:NSMakeRange(i, 1)] capitalizedString]];

Solution 5

If you profile these solutions they are much slower then doing this:

NSMutableString *capitolziedString = [NSMutableString stringWithString:originalString];
NSString *firstChar = [[capitolziedString substringWithRange:NSMakeRange(0,1)] uppercaseString];
[capitolziedString replaceCharactersInRange:NSMakeRange(0, 1) withString:firstChar];

in testing on an iphone 4 running iOS 5:
@doomspork's solution ran in 0.115750 ms
while above ran in 0.064250 ms;

in testing on an Simulator running iOS 5:
@doomspork's solution ran in 0.021232 ms
while above ran in 0.007495 ms;

View more solutions

Comments

[Rog]

yeah, optimised for cr/lf ;-) I like to let the optimiser take my temporaries out.

[dwery]

it seems that an underscore is considered a valid separator so foo_bar will be converted to "Foo_Bar"

[ArtOfWarfare]

If this function were being run repeatedly it might be of concern that your solution runs in 1/3 to 1/2 the time, but as is, we're looking for the "easiest" solution, which could be read as the most legible.

[odyth]

@ArtOfWarfare My solution isn't that much harder to read then your's is and if your going to encapsulate the solution inside a category, that you wont probably ever look at again, then you should build the fastest solution so you don't have some weird performance problem later because you wrote inefficient code.