Does NSRegularExpression support partial case insensitive?

Question

As the title states, I wonder if NSRegularExpression in both Objective-c or Swift, support partial case insensitive search?

Namely, will the pattern recognize (?ismx)? If not, is there a brief reason for this inability?

I truly appreciate your explanation.

Martin R · Accepted Answer · 2014-11-08T23:48:37.120

7

From the NSRegularExpression Class Reference:

Table 2 Regular Expression Operators

...

(?ismwx-ismwx:...)
Flag settings. Evaluate the parenthesized expression with the specified flags enabled or -disabled. ...

(?ismwx-ismwx)
Flag settings. Change the flag settings. Changes apply to the portion of the pattern following the setting. For example, (?i) changes to a case insensitive match. ...

Example:

let pattern = "(?i)f(?-i)oo"
//Or: let pattern = "(?i:f)oo"
let regex = NSRegularExpression(pattern: pattern, options: nil, error: nil)!

let string : NSString = "foo, Foo, fOO"
regex.enumerateMatchesInString(string, options: nil, range: NSMakeRange(0, string.length)) {
    (result, flags, stop) -> Void in
    println(string.substringWithRange(result.range))
}

Output:

foo
Foo

The pattern matches "foo" and "Foo" because the "f" is matched case insensitive. It does not match "fOO" because "oo" is matched case sensitive.

edited Nov 08 '14 at 23:48

answered Nov 08 '14 at 23:29

Martin R

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Is that capturing or not? – zaph Nov 08 '14 at 23:38
@Zaph: It does not (as far as I can see) introduce a new capture group. Is that what you mean? – Martin R Nov 08 '14 at 23:45
2

@Zaph: I have tested it: replacing `result.range` with `result.rangeAtIndex(1)` in the above example code throws an "out of range" exception, which means that there is no capture group in the pattern. – Martin R Nov 08 '14 at 23:52
Thank you for detailed testing and explanation! – donkey Nov 09 '14 at 01:44

Does NSRegularExpression support partial case insensitive?

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