Flutter - Validate a phone number using Regex

Question

In my futter mobile app, I am trying to validate a phone number using regex. Below are the conditions.

1. Phone numbers must contain 10 digits.

Answer 1

You could make the first part optional matching either a + or 0 followed by a 9. Then match 10 digits:

^(?:[+0]9)?[0-9]{10}$

• ^ Start of string
• (?:[+0]9)? Optionally match a + or 0 followed by 9
• [0-9]{10} Match 10 digits
• $ End of string

Regex demo

Answer 2

Validation using Regex:

String validateMobile(String value) {
String pattern = r'(^(?:[+0]9)?[0-9]{10,12}$)';
RegExp regExp = new RegExp(pattern);
if (value.length == 0) {
      return 'Please enter mobile number';
}
else if (!regExp.hasMatch(value)) {
      return 'Please enter valid mobile number';
}
return null;
}