Remove "?" from NSString IOS - ios

Question

I am trying to remove all symbols from a string, it works fine with below code for all symbols except "?".
NSString *newString = self.titleString;
NSArray *characters = #[#"<", #"!", #"#", #"#", #"$", #"%", #"^", #"&", #"*", #"(", #")", #",", #"_", #"+", #"|", #">", #"?", #" "];
for (NSString *str in characters) {
newString = [newString stringByReplacingOccurrencesOfString:str withString:#""];
}

Answer 1

You can use stringByReplacingOccurrencesOfString with the regular expression option, NSRegularExpressionSearch:
NSString *output = [input stringByReplacingOccurrencesOfString:#"[<>!##$%^&*(),_+?| ]" withString:#"" options:NSRegularExpressionSearch range:NSMakeRange(0, [input length])];
You can also take advantage of other regular expression features, e.g. replace all non-letter characters:
NSString *output = [input stringByReplacingOccurrencesOfString:#"\\P{L}" withString:#"" options:NSRegularExpressionSearch range:NSMakeRange(0, [input length])];
or not A-Z:
NSString *output = [input stringByReplacingOccurrencesOfString:#"[^a-zA-Z]" withString:#"" options:NSRegularExpressionSearch range:NSMakeRange(0, [input length])];
It just depends upon precisely what you're trying to achieve.

Answer 2

You can remove all characters in a single call using NSRegularExpression:
NSString *string = self.titleString;
NSError *error = nil;
// Prepare the regular expression that matches any of your characters
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"[<>!##$%^&*(),_+?| ]"
options:NSRegularExpressionCaseInsensitive
error:&error];
// Replace all matches with an empty string
string = [regex stringByReplacingMatchesInString:string options:0 range:NSMakeRange(0, [string length]) withTemplate:#""];

Answer 3

You have to escape the ? like that: "\?". Otherwise it won't work properly. ? only means in regex stands for 0 or 1 occurences and so you have to say to objective-c that it is a real char you want to test.

Answer 4

If this is for editing user text you might want to consider using a union of more than one NSCharacterSet - this will help it be more language-friendly when you localize/internationalize your app.
NSString *myInputText = #"asd;jkfhals#$%^%$&1asldiguhd";
NSCharacterSet *nonAlphanumeric = [[NSMutableCharacterSet alphanumericCharacterSet] invert];
NSArray *parts = [myInputText componentsSeparatedByCharactersInSet:nonAlphanumeric];
NSArray *mySafeOutputText = [parts componentsJoinedByString:#""];
It's a little non-intuitive to use the components method, but unfortunately Apple doesn't provide a stringByReplacingCharactersInSet: method. :(