NSPredicate not filtering as desired - ios

Question

Consider the following array:
NSArray *dataValues = #[#"Foo[0]", #"Foo[1].bar"];
And the following regex pattern, predicate and expected output:
NSString *pattern = #"Foo[0]";
NSPredicate *predicate = [NSPredicate predicateWithFormat: #"SELF BEGINSWITH[cd] %#", pattern];
NSArray *results = [dataValues filteredArrayUsingPredicate: predicate];
NSLog(#"matches = %ld", (long)results.count);
This prints 1 in the console as expected. If we change the pattern to:
NSString *pattern = #"Foo\\[[0-9]\\]";
I would expect this to print 2 in the console, but it prints 0. I have double escaped the outer square brackets to allow them to be parsed and expect to find strings that have the numbers 0 to 9 inside the brackets to match this expression.
I have checked the regex against the following site, which does work correctly:
http://regexr.com/3bcut
I have no warnings/errors in Xcode (6.4, 6E35b) running against the iOS 8.4 iPhone 6 Plus simulator, but why does my regex not filter as expected?

Answer 1

You could try this depending on what your needs are:
NSArray *dataValues = #[#"Foo[0]", #"Foo[1].bar"];
NSString *pattern = #"Foo[*]*";
NSPredicate *predicate = [NSPredicate predicateWithFormat: #"SELF LIKE %#", pattern];
NSArray *results = [dataValues filteredArrayUsingPredicate: predicate];
NSLog(#"matches = %ld", (long)results.count);
You could go a little more basic and use
NSMutableArray *results = [NSMutableArray array];
for (NSString *str in dataValues) {
if ([str rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet]].location != NSNotFound) {
if ([str hasPrefix:#"Foo["]) {
[results addObject:str];
}
}
}
NSLog(#"matches = %ld", (long)results.count);

Answer 2

After raising a TSI with Apple (well, who uses those things anyway?) they said I simply needed to use MATCHES instead of BEGINSWITH, which is only used for string matching - whereas I am trying to match on a regex.
My predicate should have therefore read:
NSPredicate *predicate = [NSPredicate predicateWithFormat: #"SELF MATCHES[cd] %#", pattern];