It's used to match patterns in strings, allowing you to perform more complex string manipulations, validations, and extractions.

Here's a brief overview:
1- Creating a RegExp object:
Use the RegExp class to create a regular expression object. In Flutter, you can use this class to define patterns that you want to match.

𝘙𝘦𝘨𝘌𝘹𝘱 𝘮𝘺𝘙𝘦𝘨𝘌𝘹𝘱 = 𝘙𝘦𝘨𝘌𝘹𝘱(𝘳'𝘱𝘢𝘵𝘵𝘦𝘳𝘯');

The r prefix before the string literal is used to denote a raw string.

2- Testing for a match:
Use the hasMatch method to check if a string contains a match for the regular expression.

𝘚𝘵𝘳𝘪𝘯𝘨 𝘮𝘺𝘚𝘵𝘳𝘪𝘯𝘨 = "𝘦𝘹𝘢𝘮𝘱𝘭𝘦 𝘵𝘦𝘹𝘵";
𝘪𝘧 (𝘮𝘺𝘙𝘦𝘨𝘌𝘹𝘱.𝘩𝘢𝘴𝘔𝘢𝘵𝘤𝘩(𝘮𝘺𝘚𝘵𝘳𝘪𝘯𝘨)) { 
𝘱𝘳𝘪𝘯𝘵("𝘔𝘢𝘵𝘤𝘩 𝘧𝘰𝘶𝘯𝘥!");
} 𝘦𝘭𝘴𝘦 {
𝘱𝘳𝘪𝘯𝘵("𝘕𝘰 𝘮𝘢𝘵𝘤𝘩 𝘧𝘰𝘶𝘯𝘥.");
}

3- Finding matches:
Use the allMatches method to find all matches in a given string.

𝘚𝘵𝘳𝘪𝘯𝘨 𝘮𝘺𝘚𝘵𝘳𝘪𝘯𝘨 = "𝘦𝘹𝘢𝘮𝘱𝘭𝘦 𝘵𝘦𝘹𝘵 𝘸𝘪𝘵𝘩 𝘱𝘢𝘵𝘵𝘦𝘳𝘯 𝘱𝘢𝘵𝘵𝘦𝘳𝘯";
𝘓𝘪𝘴𝘵<𝘔𝘢𝘵𝘤𝘩> 𝘮𝘢𝘵𝘤𝘩𝘦𝘴 = 𝘮𝘺𝘙𝘦𝘨𝘌𝘹𝘱.𝘢𝘭𝘭𝘔𝘢𝘵𝘤𝘩𝘦𝘴(𝘮𝘺𝘚𝘵𝘳𝘪𝘯𝘨);
𝘧𝘰𝘳 (𝘔𝘢𝘵𝘤𝘩 𝘮𝘢𝘵𝘤𝘩 𝘪𝘯 𝘮𝘢𝘵𝘤𝘩𝘦𝘴) { 
𝘱𝘳𝘪𝘯𝘵("𝘔𝘢𝘵𝘤𝘩 𝘧𝘰𝘶𝘯𝘥 𝘢𝘵 ${𝘮𝘢𝘵𝘤𝘩.𝘴𝘵𝘢𝘳𝘵} - ${𝘮𝘢𝘵𝘤𝘩.𝘦𝘯𝘥}: ${𝘮𝘢𝘵𝘤𝘩.𝘨𝘳𝘰𝘶𝘱(0)}");
}

4- Extracting matched groups:
If your regular expression contains groups, you can access them using the group method of the Match object.

𝘙𝘦𝘨𝘌𝘹𝘱 𝘮𝘺𝘙𝘦𝘨𝘌𝘹𝘱 = 𝘙𝘦𝘨𝘌𝘹𝘱(𝘳'(\𝘥{2})/(\𝘥{2})/(\𝘥{4})');
𝘚𝘵𝘳𝘪𝘯𝘨 𝘥𝘢𝘵𝘦𝘚𝘵𝘳𝘪𝘯𝘨 = "01/17/2024";
𝘔𝘢𝘵𝘤𝘩 𝘮𝘢𝘵𝘤𝘩 = 𝘮𝘺𝘙𝘦𝘨𝘌𝘹𝘱.𝘧𝘪𝘳𝘴𝘵𝘔𝘢𝘵𝘤𝘩(𝘥𝘢𝘵𝘦𝘚𝘵𝘳𝘪𝘯𝘨);
𝘪𝘧 (𝘮𝘢𝘵𝘤𝘩 != 𝘯𝘶𝘭𝘭) { 
𝘚𝘵𝘳𝘪𝘯𝘨 𝘥𝘢𝘺 = 𝘮𝘢𝘵𝘤𝘩.𝘨𝘳𝘰𝘶𝘱(1);
 𝘚𝘵𝘳𝘪𝘯𝘨 𝘮𝘰𝘯𝘵𝘩 = 𝘮𝘢𝘵𝘤𝘩.𝘨𝘳𝘰𝘶𝘱(2);
 𝘚𝘵𝘳𝘪𝘯𝘨 𝘺𝘦𝘢𝘳 = 𝘮𝘢𝘵𝘤𝘩.𝘨𝘳𝘰𝘶𝘱(3);
 𝘱𝘳𝘪𝘯𝘵("𝘋𝘢𝘵𝘦: $𝘮𝘰𝘯𝘵𝘩/$𝘥𝘢𝘺/$𝘺𝘦𝘢𝘳");
}

5- Testing in a Flutter application:
You can use regular expressions in various scenarios in Flutter, such as form validations, parsing data, or filtering lists. For example, you might use a regular expression to validate an email address entered in a form.

𝘙𝘦𝘨𝘌𝘹𝘱 𝘦𝘮𝘢𝘪𝘭𝘙𝘦𝘨𝘌𝘹𝘱 = 𝘙𝘦𝘨𝘌𝘹𝘱(𝘳'^[\𝘸-]+(\.[\𝘸-]+)*@([\𝘸-]+\.)+[𝘢-𝘻𝘈-𝘡] {2,7}$');
𝘚𝘵𝘳𝘪𝘯𝘨 𝘦𝘮𝘢𝘪𝘭𝘈𝘥𝘥𝘳𝘦𝘴𝘴 = "𝘦𝘹𝘢𝘮𝘱𝘭𝘦@𝘦𝘮𝘢𝘪𝘭.𝘤𝘰𝘮";
𝘪𝘧 (𝘦𝘮𝘢𝘪𝘭𝘙𝘦𝘨𝘌𝘹𝘱.𝘩𝘢𝘴𝘔𝘢𝘵𝘤𝘩(𝘦𝘮𝘢𝘪𝘭𝘈𝘥𝘥𝘳𝘦𝘴𝘴)) {
𝘱𝘳𝘪𝘯𝘵("𝘝𝘢𝘭𝘪𝘥 𝘦𝘮𝘢𝘪𝘭 𝘢𝘥𝘥𝘳𝘦𝘴𝘴");
} 𝘦𝘭𝘴𝘦 {
 𝘱𝘳𝘪𝘯𝘵("𝘐𝘯𝘷𝘢𝘭𝘪𝘥 𝘦𝘮𝘢𝘪𝘭 𝘢𝘥𝘥𝘳𝘦𝘴𝘴");
}

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