Howto get groups by repeated pattern with qantizer in regular expression

Question

I have the following string:

(a,b,c,d,e)

I want to get out all comma separated values by a regular expression.

If I put away the brackets

a,b,c,d,e

and use the following regular expression:

([^,]),?

I get out one match as well as one group for each comma separated value.

But if I want to do with concluding brackets using the regular expression:

\((([^,]),?)+\)

I still get only one match and one group. The group contains only the last comma separated value.

I tried also with group captures like:

(?:....)
(...?)
(...)?

but I cannot get out the comma separated values by regular expression groups.

How can I do this, when the comma separated values are enclosed in brackets?

Answer 1

I found it out. Using C# you can use the property Captures in the Match Collection.

Using Regex:

\((([^,]),?)+\)

Do:

        string text = "(a,b,c,d,e)";
        Regex rgx = new Regex("\\((([^,]),?)+\\)");
        MatchCollection matches = rgx.Matches(text);

Then you have 1 item with the following 3 groups in the matchcollection:

[0]: \((([^,]),?)+\) => (a,b,c,d,e)
[1]: ([^,]),?+ => value and optional comma, eg. a, or b, or e
[2]: [^,] => value only, eg. a or b or ...

The list captures within the group stores each extracted value by quantizer. So use group [2] and captures to get out all the values.

So the solution is:

        string text = "(a,b,c,d,e)";
        Regex rgx = new Regex("\\((([^,]),?)+\\)");
        MatchCollection matches = rgx.Matches(text);

        //now get out the captured calues
        CaptureCollection captures = matches[0].Groups[2].Captures;

        //and extract them to list
        List<string> values = new List<string>();
        foreach (Capture capture in captures)
        {
            values.Add(capture.Value);
        }