Flutter getting string between special characters using RegEx-CodePudding

I have string like this one ==here==. How can I get here using RegEx pattern.

I know I can use .substring like

    const pattern = "==";
    const str = "==here==";
    final start = str.indexOf(pattern)   pattern.length;
    final end = str.lastIndexOf(pattern);

    final sub = str.substring(start, end);

    expect(sub, 'here');

for this but I want to use regex pattern so that I could get first match correctly.

What I want exactly is to get first string that is wrapped in two == even if there are thousand matches.

CodePudding user response：

The simplest RegExp just matches ==(something)== and uses the capture. Here it uses a non-greedy match so that it finds the first following ==.

var re = RegExp(r'==([^]*?)==');
var sub = re.firstMatch(str)?[1];

If you need the RegExp match itself to be the string between the ==s, you can use look-behind and look-ahead:

var re = RegExp(r'(?<===)[^]*?(?===)');
var sub = re.firstMatch(str)?[0];

CodePudding user response：

String find(String str) {
RegExp exp = RegExp(r'==([^]*?)==');
RegExpMatch? match = exp.firstMatch(str);
return match?.group(1) ?? '';

}