Unable to get substring in flutter and wrong string length

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....

The issue can be your charset. It's because when I try .split('') in the first one, it returns � 12 times. I can't help, but you might focus on the charsets. — Emre
– Emre, Commented Nov 30, 2022 at 11:11

eamirho3ein · Accepted Answer · 2022-11-30 11:36:15Z

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.

edited Nov 30, 2022 at 11:36

answered Nov 30, 2022 at 11:29

eamirho3ein

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2 Comments

Omi Shah Over a year ago

instead of calling str.runes.toList() within the loop, store in a variable and then access within the loop..

Ravindra S. Patil Over a year ago

@eamirho3ein, have you look this question please try to give answer of question

abichinger · Accepted Answer · 2022-11-30 11:17:58Z

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

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