NSPredicate with regular expression

PredicateRegularExpression.m

- (void)testRegularExpression
{
    // \d+      regular expression pattern
    // \\d+     pattern with escape for string
    // \\\\d+   pattern with re-escape for predicate format

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES '\\d+'"];
    NSLog(@"%@", predicate);
    // SELF MATCHES "d+"

    predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES '\\\\d+'"];
    NSLog(@"%@", predicate);
    // SELF MATCHES "\\d+"

    predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", @"\\d+"];
    NSLog(@"%@", predicate);
    // SELF MATCHES "\\d+"

    BOOL result = NO;
    result = [predicate evaluateWithObject:@"123abc"];
    NSLog(@"%d", result);
    // 0
    
    result = [predicate evaluateWithObject:@"123456"];
    NSLog(@"%d", result);
    // 1

    result = [predicate evaluateWithObject:@"abcdef"];
    NSLog(@"%d", result);
    // 0
}