Replace 0 in a phone number with country code

I use a library to get phone numbers from a mobile device but most of the numbers start with 0 for example:03004444444.But I noticed whatsapp converted it to country code(+92).I want to know how how to replace 0 with a country code in flutter.

To replace '0' with country code '+92' you can easily do that with replaceFirst method. But unfortunately it's not as simple as that. We need to check it whether the phone is a valid phone first, whether it's already '+92' in there, or whether it's started with leading '3'

void main() {
  //   final String phone = '03004444444';
  final String phone = '0312345678901';


  print('original: $phone');

  // this regex assume after digit '3' there should be 9-11 characters after it
  final phoneRegex = RegExp(r'(0|\+?92)3\d{9,11}$');

  if (phoneRegex.hasMatch(phone)) {
    // if start with '0' then replace it with '+92'
    final String replaced = phone.startsWith('0') ? 
                            phone.replaceFirst('0', '+92') : phone;

    print('replaced: $replaced');
  } else {
    print('invalid phone');
  }
} 

You can check the code in this dartpad.

As for dial code:

WidgetsBinding.instance.window.locale.countryCode

will only give you country code like 'US' not dial code.

For dial code, there are many ways of getting it,

I would recommend using this package called country_codes

But in order to be used in widget you need make it StatefulWidget and then put code initialization in initState

import 'package:country_codes/country_codes.dart';

...

String? dialCode;

@override
void initState() {
  super.initState();

  WidgetsBinding.instance.addPostFrameCallback((timeStamp) async {
    // Optionally, you may provide a `Locale` to get countrie's localizadName
    await CountryCodes.init();
    final CountryDetails details = CountryCodes.detailsForLocale();
    setState(() {
      dialCode = details.dialCode;
    });
  });
}