CODEWITHSUNDEEP
iosobjective-cstringcocoacocoa-touch
Omar
Omar

Reputation: 2155

Objective-C - Remove last character from string

In Objective-C for iOS, how would I remove the last character of a string using a button action?

Upvotes: 154

Views: 113086

Answers (4)

Marc Charbonneau
Marc Charbonneau

Reputation: 40507

In your controller class, create an action method you will hook the button up to in Interface Builder. Inside that method you can trim your string like this:


if ([string length] > 0) {
    string = [string substringToIndex:[string length] - 1];
} else {
    //no characters to delete... attempting to do so will result in a crash
}





If you want a fancy way of doing this in just one line of code you could write it as:

string = [string substringToIndex:string.length-(string.length>0)];

*Explanation of fancy one-line code snippet:

If there is a character to delete (i.e. the length of the string is greater than 0)
     (string.length>0) returns 1 thus making the code return:
          string = [string substringToIndex:string.length-1];

If there is NOT a character to delete (i.e. the length of the string is NOT greater than 0)
     (string.length>0) returns 0 thus making the code return:
          string = [string substringToIndex:string.length-0];
     Which prevents crashes.

Upvotes: 424

user1071136
user1071136

Reputation: 15725

The solutions given here actually do not take into account multi-byte Unicode characters ("composed characters"), and could result in invalid Unicode strings.

In fact, the iOS header file which contains the declaration of substringToIndex contains the following comment:

Hint: Use with rangeOfComposedCharacterSequencesForRange: to avoid breaking up composed characters

See how to use rangeOfComposedCharacterSequenceAtIndex: to delete the last character correctly.

Upvotes: 8

Dave DeLong
Dave DeLong

Reputation: 243146

If it's an NSMutableString (which I would recommend since you're changing it dynamically), you can use:

[myString deleteCharactersInRange:NSMakeRange([myRequestString length]-1, 1)];

Upvotes: 54

Harald Scheirich
Harald Scheirich

Reputation: 9764

The documentation is your friend, NSString supports a call substringWithRange that can shorten the string that you have an return the shortened String. You cannot modify an instance of NSString it is immutable. If you have an NSMutableString is has a method called deleteCharactersInRange that can modify the string in place

...
NSRange r;
r.location = 0;
r.size = [mutable length]-1;
NSString* shorted = [stringValue substringWithRange:r];
...

Upvotes: 6

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