How to capitalize the first word of the sentence in Objective-C?

Here is another go at it:

NSString *txt = @"hi my friends!";
txt = [txt stringByReplacingCharactersInRange:NSMakeRange(0,1) withString:[[txt substringToIndex:1] uppercaseString]];

For Swift language:

txt.replaceRange(txt.startIndex...txt.startIndex, with: String(txt[txt.startIndex]).capitalizedString)