Unable to get substring in flutter and wrong string length - flutter

Question

I am working on application to show mobile contact list with initials in a circle, but not getting initial character for some contact names.
In below code, first name is from mobile's contact list and second one I have typed from keyboard.
I am able to get correct length and also first character of the second name, but length for first name is double and also not able to get first character (it gives �).
print("𝙽𝚊𝚐𝚎𝚜𝚑".substring(0,1)); //�
print("𝙽𝚊𝚐𝚎𝚜𝚑".length); //12
print("Nagesh".substring(0,1)); //N
print("Nagesh".length); //6
Thankyou in advance for answering....

Answer 1

You can use this function to use substring with unicode:
subOnCharecter({required String str, required int from, required int to}) {
var runes = str.runes.toList();
String result = '';
for (var i = from; i < to; i++) {
result = result + String.fromCharCode(runes[i]);
}
return result;
}
and you can use it like this:
print(subOnCharecter(str: "𝙽𝚊𝚐𝚎𝚜𝚑", from: 0, to: 2)); // 𝙽𝚊
print(subOnCharecter(str: "Nagesh", from: 0, to: 2)); // Na
you can use this function instead of default substring.

Answer 2

The strings look similar, but they consist of different unicode characters.
Character U+1d67d "𝙽" is not the same as U+004e "N".
You can use str.runes.length to get the number of unicode characters.
A detailed explanation why the string length is different can be found here
example:
void main() {
var mobileStr = "𝙽𝚊𝚐𝚎𝚜𝚑";
var keyboardStr = "Nagesh";
analyzeString(mobileStr);
print("");
analyzeString(keyboardStr);
}
void analyzeString(String s) {
Runes runes = s.runes; // Unicode code-points of this string
var unicodeChars = runes.map((r) => r.toRadixString(16)).toList();
print("String: $s");
print("String length: ${s.length}");
print("Number of runes: ${runes.length}");
print("unicode characters: ${unicodeChars.join(" ")}");
}
// OUTPUT
// String: 𝙽𝚊𝚐𝚎𝚜𝚑
// String length: 12
// Number of runes: 6
// unicode characters: 1d67d 1d68a 1d690 1d68e 1d69c 1d691
// String: Nagesh
// String length: 6
// Number of runes: 6
// unicode characters: 4e 61 67 65 73 68