Question

Is there a clean way to get a string containing only allowed characters?

for example:

NSString* myStr = @"a5&/Öñ33";
NSString* allowedChars = @"abcdefghijklmnopqrstuvwxyz0123456789";
NSString* result = [myStr stringWIthAllowedChrs:allowedChars];

result should now be @"a533";

Answer 1

It’s not the cleanest, but you could separate the string using a character set, and then combine the resulting array using an empty string.

// Create a character set with every character not in allowedChars
NSCharacterSet *charSet = [[NSCharacterSet characterSetWithCharactersInString:allowedChars] invertedSet];
// Split the original string at any occurrence of those characters
NSArray *splitString = [myStr componentsSeparatedByCharactersInSet:charSet];
// Combine the result into a string
NSString *result = [splitString componentsJoinedByString:@""];