CODEWITHSUNDEEP
objective-cregex
Daumantas Versockas
Daumantas Versockas

Reputation: 777

Objective-C Find first matching regular expression in string

I have a task with regular expressions. I have a list of NSRegularExpression objects with different patterns. Also I have a NSString object to define a source. I need to find which regular expression (from the given list) matches for the BEGINNING of source.

Is there a way to do it with Objective-C?

For example:

Expressions patterns

  1. [a-z]
  2. [A-Z]
  3. [1-9]

source

Hello32

Result

Expression no 2 fits for the beginning of source, because of letter H.

Upvotes: 0

Views: 267

Answers (2)

Nikolai Ruhe
Nikolai Ruhe

Reputation: 81858

Why don't you just try them out?

NSString *testString = @"Hello";

NSArray *patterns = @[
    @"[a-z]",
    @"[A-Z]",
    @"[1-9]",
];

for (NSString *pattern in patterns) {
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
                                                                           options:0
                                                                             error:NULL];
    BOOL matchAtStart = [regex rangeOfFirstMatchInString:testString
                                                 options:0
                                                   range:(NSRange){0, testString.length}].location == 0;
    NSLog(@"'%@': %@", pattern, @(matchAtStart));
}

Upvotes: 1

Mariano
Mariano

Reputation: 6511

You can prepend \A(?: and append ) to each pattern to force them to match at the beggining of the string. The patterns provided as example would become:

\A(?:[a-z])
\A(?:[A-Z])
\A(?:[1-9])
  • \A is an anchor to the beggining of the string (behaves exactly like ^ when the Multiline flag is not set).

Upvotes: 0

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