Replace the whole string with a new text using a regular expression [closed] - regex

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I want to replace a String data with a new one where I do not know what is inside the string as it may be empty, spaces, alphabets, numerics, special characters, mix, etc. It is simple as below
String randomString = "Some Old String"; // It will be any string or may be an empty string too
print("Old String ${randomString}"); // Output = Some Old String
randomString = "Some New String";
print("New String ${randomString}"); // Output = Some New String
But due to some limitations (no need to define here), I can't use the upper process. I would like to do this with only sub-functions like .replaceAll, .replaceRange, .replaceMap, .replaceFirst, .replaceFirstMap etc. For that, I tried following.
String randomString = ""; // It will be any string or maybe an empty string too
print("Old String ${randomString}"); // Output = ""
randomString.replaceAll(RegExp(r"/\W/g"),"Some New String");
print("New String ${randomString}"); // Output = "" (Showing Empty)
What should be the regex to select all and replace with alphabets, digits, special characters, spaces, empty, etc.?
I am currently using RegExp(r"/\W/g") so tell me the correct one for my need.
Live DEMO:
jdoodle.com/ia/DVm

Answer 1

You can achieve this by creating TextInputFormatter class and pass it to inputFormatters parameter in TextField, here's an example:
class ReplaceTextInputFormatter extends TextInputFormatter {
#override
TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
// TODO replace the [[oldValue] with [newValue] for your needs
return newValue;
}
}
TextField(
inputFormatters: [ReplaceTextInputFormatter()],
)
Edit after #Muhammad Hassan's comment about no need for widgets.
We can achieve this using replaceRange from 0 to the string length, for example:
randomString.replaceRange(0, s.length, 'replacement');