NSRegularExpression Returns Invalid Range

Question

When I run the following code in a Playground, I get an invalid range as a result:

import Cocoa

var error: NSError?
var captureGroups: [String] = []
var input = "http://www.google.com"

var pattern = "(https?|ftp|file|gopher|mailto|news|nntp|telnet|wais)://[a-zA-Z0-9_@]+([.:][a-zA-Z0-9_@]+)*/?[a-zA-Z0-9_?,%#~&/\\-]+([:.][a-zA-Z0-9_?,%#~&/\\-]+)*"

var internalExpression = NSRegularExpression(pattern: pattern, options: .CaseInsensitive, error: &error)!

if let match = internalExpression.firstMatchInString(input, options: nil, range: NSMakeRange(0, count(input))) {

    match.numberOfRanges // 4
    match.rangeAtIndex(0) // (0, 21)
    match.rangeAtIndex(1) // (0, 4)
    match.rangeAtIndex(2) // (17, 3)
    match.rangeAtIndex(3) // (9223372036854775807,0)
}

This code has worked for other regular expressions, it seems to be only this one that is giving it trouble. I am not a RegEx expert, so I am unsure as to how I should proceed.

9223372036854775807 is NSIntegerMax aka NSNotFound, i.e. there is no match for the last capture group. What result do you expect? — Martin R, Jul 19 '15 at 16:34
@MartinR I would have expected the match to fail, but I am not a RegEx expert. Is there a preferred method to test for this case? I am relatively new to Cocoa as well. — user3338852, Jul 19 '15 at 16:59

score 1 · Accepted Answer · answered Jul 19 '15 at 17:03

1

You do an if test like this:

if match.rangeAtIndex(3).location != NSNotFound {
    // Do if found result.
} else {
    // Handle error.
}

answered Jul 19 '15 at 17:03

Cai

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score 0 · Answer 2 · answered Jul 19 '15 at 17:43

if you want to parse a URL, it's probably easiest to use NSURL:

if let url = NSURL(string: input) {
    println(url.scheme)
    println(url.host)
    println(url.path)
    println(url.pathComponents)
    println(url.query)
}

If you want help fixing the regex and understanding why you received NSNotFound, you should clearly describe what you were hoping to parse out of it. But when dealing with URLs, NSURL is easiest.

NSRegularExpression Returns Invalid Range

2 Answers2