Question

I have a huge amount of NSStrings in a database that get passed to a view controller in an iOS app. They are formatted as “This is a message with $specially formatted$ content”.

However, I need to change the ‘$’ at the start of the special formatting with a ‘[‘ and the ‘$’ at the end with ‘]’. I have a feeling I can use an NSScanner but so far all of my attempts have produced wackily concatenated strings!

Is there a simple way to recognise a substring encapsulated by ‘$’ and swap them out with start/end characters? Please note that a lot of the NSStrings have multiple ‘$’ substrings.

Thanks!

Answer 1

You can use regular expressions:

NSMutableString *str = [@"Hello $World$, foo $bar$." mutableCopy];

NSRegularExpression *regex;
regex = [NSRegularExpression regularExpressionWithPattern:@"\\$([^$]*)\\$"
                                                  options:0
                                                    error:NULL];
[regex replaceMatchesInString:str
                      options:0
                        range:NSMakeRange(0, [str length])
                 withTemplate:@"[$1]"];
NSLog(@"%@", str);
// Output:
// Hello [World], foo [bar].

The pattern @"\\$([^$]*)\\$" searches for

$<zero_or_more_characters_which_are_not_a_dollarsign>$

and all occurrences are then replaced by [...]. The pattern contains so many backslashes because the $ must be escaped in the regular expression pattern.

There is also stringByReplacingMatchesInString if you want to create a new string instead of modifying the original string.