How to check if a Regex is valid or not in Objective-C?

Question

I got a Regex from an API. I need to validate the regex if it is valid or not.

This is a sample regex pattern:

/^[a-z0-9_-]{6,18}$/

I need to validate this string.

Edit: I have tried initwithpattern with a invalid regex [ , But its not throwing any error.

Answer 1

You should initialize an instance of NSRegularExpression with the given regex pattern and check whether that NSRegularExpression is NULL .

NSString *regexString = @"/^[a-z0-9_-]{6,18}$/";
NSError *error = NULL;
NSRegularExpression *regex = 
    [NSRegularExpression regularExpressionWithPattern:regexString 
                                              options:0 
                                                error:&error];

if (!regex) {
    //regex is invalid
}