What's wrong with my ActionScript Regex?

Question

I am trying pull a field out of a string and return it.

My function:

public function getSubtype(ut:String):String {
            var pattern:RegExp = new RegExp("X=(\w+)","i");
            var nut:String = ut.replace(pattern, "$1");
            trace("nut is " + nut);
            return nut;
        }

I'm passing it the string:

http://foo.bar.com/cgi-bin/ds.pl?type=boom&X=country&Y=day&Z=5

the trace statements return the above string with out modification.

I've tried the pattern out on Ryan Swanson's Flex 3 Regular Expresion Explorer and it returns: X=country. My wished for result is "country".

Must be obvious, but I can't see it. Any help will be appreciated.

TB

changed my function to the following and it works:

public function getSubtype2(ut:String):String {
            trace("searching " + ut);
            var pattern:RegExp = new RegExp("X=([a-z]+)");
            var r:Object = pattern.exec(ut);
            trace("result is " + r[1]);
            return r[1].toString();

Interestingly, though, using X=(\w+) does not match and causes an error. ???? }

Yes, that's a better way. And if AS is like Java, you have to try: new RegEx("X=(\\w+)", "i"); — PhiLho
– PhiLho, Commented Aug 26, 2009 at 19:11
In a regex literal you use one backslash: /X=(\w+)/. You're writing it as a string literal to pass it to the RegExp constructor: new RegExp("X=(\\w+)"); that's why you have to use two backslashes. ref: livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/RegExp.html — Alan Moore
– Alan Moore, Commented Mar 10, 2010 at 12:10

Virusescu · Accepted Answer · 2009-08-27 12:55:07Z

1

The replace method is used for replacing. That is if you want to modify the given string. Replacing given portion with his own occurrence produces the same string. I think you are looking for the match method, that produces an array of matches, see below.

function getSubtype(ut:String):String {
            var pattern:RegExp = new RegExp("X=([a-z]+)","i");
            var nut:Array = ut.match(pattern);
            trace("nut is " + nut[1]);
            return nut[1];
}

nut[0] beeing the full matched string, followed by nut[1] the first brackets group and so on.

answered Aug 27, 2009 at 12:55

Virusescu

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2 Comments

Virusescu Over a year ago

Also, in order for your first pattern with \w to work, if you write it between quotes, then you must escape the \ char. Else it would work only if written like var pattern:RegExp = /X=(\w+)/;

Todd Over a year ago

Thanks a bunch! All the wrinkles to learning a new language :-)

AnthonyWJones · Accepted Answer · 2009-08-26 16:28:54Z

1

The replace method does not mutate the string it operates on, it returns a new string. Try:-

var nut:String = ut.replace(pattern, "$1");

answered Aug 26, 2009 at 16:28

AnthonyWJones

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1 Comment

Todd Over a year ago

Just tried your suggestion. Unfortunately, still same result.

PhiLho · Accepted Answer · 2009-08-26 16:28:37Z

0

Note: I don't know ActionScript...

Your RE Explorer seems to return the matched pattern, see if there is a possibility to see the captures as well.

And if AS behaves like most languages I know, your replace() call replaces X=country with country.

answered Aug 26, 2009 at 16:28

PhiLho

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Randy Sugianto 'Yuku' · Accepted Answer · 2009-08-27 06:46:15Z

0

Instead of

 var pattern:RegExp = new RegExp("X=(\w+)","i");

You can write this:

 var pattern:RegExp = /X=(\w+)/i;

Then you will not have problems with backslashes.

answered Aug 27, 2009 at 6:46

Randy Sugianto 'Yuku'

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bug-a-lot · Accepted Answer · 2010-03-10 11:24:16Z

0

var pattern : RegExp = /[\\?&]X=([^&#]*)/g;
var XValue : String = pattern.exec(ut)[1];

See http://livedocs.adobe.com/flex/3/langref/RegExp.html#exec%28%29 for further explanations.

I have also found this flex regexp testing tool to be quite helpful.

answered Mar 10, 2010 at 11:24

bug-a-lot

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