Question

How is it possible to perform a matching of string, just like regex?

For example i have an array of strings, I want to match if these string is in the format of "abc def xxx", which xxx is number like 1, 11, 12, 100, 111, etc.

How can I achieve this?

Answer 1

The arrays:

NSArray *array1 = [NSArray arrayWithObjects:@"abc def 1", @"abc def 64", @"abc def 853", @"abc def 14", nil];
NSArray *array2 = [NSArray arrayWithObjects:@"abc def 3", @"abc def 856", @"abc def 36", @"abc def 5367", nil];

The regular expression:

NSString *regex = @"abc def [0-9]{1,3}";

To check if all strings in the array matche the regex:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ALL description MATCHES %@", regex];
BOOL allStringsMatch = [predicate evaluateWithObject:array1]; 
// OUTPUT: YES
allStringsMatch = [predicate evaluateWithObject:array2];
// OUTPUT: NO

All objects in array1 matches the regex, but array2 contains the string @”abc def 5367″ which doesn’t match the regex.

To get the matched strings:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"description MATCHES %@", regex];
NSArray *unmatchedStrings = [array2 filteredArrayUsingPredicate:predicate];
// OUTPUT: { @"abc def 3", @"abc def 856", @"abc def 36" }

To get the unmatched strings:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"NOT description MATCHES %@", regex];
NSArray *unmatchedStrings = [array2 filteredArrayUsingPredicate:predicate];
// OUTPUT: { @"abc def 5367" }

Note that here “description” in predicate is the - description method of NSString.