In iOS how to check string against regular expression with boolean result

You should read documentation.

Here is an example code how to do this in general:

- (BOOL)checkString:(NSString *)string {

    NSString *const expression = @"^\\d{3}[-]\\d{2}[-]\\d{4}$"; // insert yours
    NSError *error = nil;

    NSRegularExpression * const regExpr = 
    [NSRegularExpression regularExpressionWithPattern:expression 
                                options:NSRegularExpressionCaseInsensitive 
                                error:&error];

    NSTextCheckingResult * const matchResult = [regExpr firstMatchInString:string
                              options:0 range:NSMakeRange(0, [string length])];

   return matchResult ? YES : NO; 
}