Replace characters in NSString

Question

I am trying to replace all characters except last 4 in a String with *'s.
In objective-c there is a method in NSString class replaceStringWithCharactersInRange: withString: where I would give it range (0,[string length]-4) ) with string @"*". This is what it does: 123456789ABCD is modified to *ABCD while I am looking to make ********ABCD. I understand that it replaced range I specified with string object. How to accomplish this ?

Answer 1

I'm not sure why the accepted answer was accepted, since it only works if everything but last 4 is a digit. Here's a simple way:

NSMutableString * str1 = [[NSMutableString alloc]initWithString:@"1234567890ABCD"];
NSRange r = NSMakeRange(0, [str1 length] - 4);
[str1 replaceCharactersInRange:r withString:[[NSString string] stringByPaddingToLength:r.length withString:@"*" startingAtIndex:0]];
NSLog(@"%@",str1);

Answer 2

NSError *error;

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"\\d" options:NSRegularExpressionCaseInsensitive error:&error];

NSString *newString = [regex stringByReplacingMatchesInString:string options:0 range:NSMakeRange(0, [string length]) withTemplate:@"*"];