String Manipulation in Objective-C

Gotten a hold on how to fetch and write to variables in Objective-C, now it's time to learn how to do something more useful with them! Right now, I'm primarily trying to figure out how string manipulation works. In particular, I'm looking for the following functions:

• Concatenation
• Finding the length of开发者_如何学Python a string (especially multi-byte/UTF-8 strings; I do a lot of work with East Asian languages)
• Pulling just a portion of a string (e.g. the "foobar" out of "abcfoobarxyz")
• Searching within a string (see the above example)
• Changing case (upper, lower, title if it's simple to do)
• Exploding/Imploding strings (e.g. creating and getting information from comma-separated lists)
• Find/Replace within strings
• Any other generally useful string functions that might be available

---

Examples: Concatenation:

- (NSString*) concatenateString:(NSString*)stringA withString:(NSString*)stringB
{  
    NSString *finalString = [NSString stringWithFormat:@"%@%@", stringA,
                                                       stringB];
    return finalString;
}
// The advantage of this method is that it is simple to put text between the
// two strings (e.g. Put a "-" replace %@%@ by %@ - %@ and that will put a
// dash between stringA and stringB

String Length:

- (int) stringLength:(NSString*)string
{
    return [string length];
    //Not sure for east-asian languages, but works fine usually
}

Remove text from string:

- (NSString*)remove:(NSString*)textToRemove fromString:(NSString*)input
{
   return [input stringByReplacingOccurrencesOfString:textToRemove
                                           withString:@""];
}

Uppercase / Lowercase / Titlecase:

- (NSString*)uppercase:(NSString*)stringToUppercase
{
   return [stringToUppercase uppercaseString];
}

- (NSString*)lowercase:(NSString*)stringToLowercase
{
   return [stringToLowercase lowercaseString];
}

- (NSString*)titlecase:(NSString*)stringToTitleCase
{
   return [stringToTitleCase capitalizedString];
}

Find/Replace

- (NSString*)findInString:(NSString*)string
        replaceWithString:(NSString*)stringToReplaceWith
{
   return [input stringByReplacingOccurrencesOfString:string
                                           withString:stringToReplaceWith];
}

I hope this helps!

PS: Don't forget to check the documentation, and Google is your friend. Good luck

---

In Xcode, press CMD-SHIFT-D and search for NSString.h, NSMutableString and/or NSScanner

Open those files and look at all the things you can do with NSStrings. This should tell you what functions there are.

By the way, this should become second nature to you as you'll be using this a lot to find out what the functions and/or delegates are.

---

Here's a "title case" routine for you:

- (NSString *) stringToTitleCase: (NSString *) inString
{
    NSString *firstLetter = [inString substringWithRange: NSMakeRange(0, 1)];
    NSString *theRest = [inString substringWithRange: NSMakeRange(1, [inString length]-1)];

    return [NSString stringWithFormat: @"%@%@", [firstLetter uppercaseString], theRest];
}

---

- (NSString *) stringToTitleCase: (NSString *) inString
{
    NSString *firstLetter = [inString substringWithRange: NSMakeRange(0, 1)];
    NSString *theRest = [inString substringWithRange: NSMakeRange(1, [inString length]-1)];

    return [NSString stringWithFormat: @"%@%@", [firstLetter uppercaseString], theRest];
}