How to reverse only hebrew chars on a string dart? - flutter

Question

I would like to reverse only hebrew chars in a string .
For example :
input: 1234 בלה בלה בלה
output': הלב הלב הלב 1234

Answer 1

Note that for the algorithm below to work you will need to manually add all the Hebrew characters to the list named chars I have only added the 3 Hebrew chars you specified in your example
Note that you could populate the char List using a json array if you can find one online. How to get json from the web
Create List of Hebrew characters
final List<String> chars = <String>[
"ב",
"ל",
"ה",
];
Create temp String from original string with only Hebrew characters, but in reverse
String temp = "";
for (int i = widget.reverseString.length - 1; i >= 0; i--) {
if (chars.contains(widget.reverseString[i])) {
temp += widget.reverseString[i];
}
}
Replace occurrences of Hebrew characters in original string with temp values
int tempIndex = 0;
String reveredString = widget.reverseString;
for (int r = 0; r < widget.reverseString.length; r++) {
if (chars.contains(widget.reverseString[r])) {
reveredString = _replaceCharAt(reveredString, r, temp[tempIndex]);
tempIndex++;
}
}
Full Example:
//ref:
//https://www.geeksforgeeks.org/reverse-a-string-without-affecting-special-characters/
import 'package:flutter/material.dart';
class ReverseHebrew extends StatefulWidget {
final String reverseString;
const ReverseHebrew({
Key? key,
required this.reverseString,
}) : super(key: key);
#override
State<StatefulWidget> createState() {
return _ReverseHebrewState();
}
}
class _ReverseHebrewState extends State<ReverseHebrew> {
/*
This list must be manually populated to include all Hebrew characters for this
code to properly work.
*/
final List<String> chars = <String>[
"ב",
"ל",
"ה",
];
String _replaceCharAt(String oldString, int index, String newChar) {
return oldString.substring(0, index) +
newChar +
oldString.substring(index + 1);
}
String _reverse() {
// copy hebrew chars to temp in reverse order
String temp = "";
for (int i = widget.reverseString.length - 1; i >= 0; i--) {
if (chars.contains(widget.reverseString[i])) {
temp += widget.reverseString[i];
}
}
// replace occurrences of Hebrew chars in the original string with
// the reversed values in temp
int tempIndex = 0;
String reveredString = widget.reverseString;
for (int r = 0; r < widget.reverseString.length; r++) {
if (chars.contains(widget.reverseString[r])) {
reveredString = _replaceCharAt(reveredString, r, temp[tempIndex]);
tempIndex++;
}
}
// return reversed string
return reveredString;
}
#override
Widget build(BuildContext context) {
return Text(_reverse());
}
}
void main() {
runApp(
MaterialApp(
home: Scaffold(
body: Center(
child: Column(
children: [
Text("Original: 1234 בלה בלה בלה"),
Text("Reversed:"),
ReverseHebrew(
reverseString: "בלה בלה בלה 1234",
),
],
),
),
),
),
);
}
Ref: Geeks for Geeks Algorithm

Answer 2

Seemingly Hebrew has the range \u0590-\u05fe (according to this nice JavaScript Unicode Regex generator).
So we can use this to find and reverse Hebrew only from any given string.
Here is the perfect working example:
String reverseHebrew(String text) {
text = text.splitMapJoin(
RegExp(r'[\u0590-\u05FF]+'),
onMatch: (m) => m.group(0).split('').reversed.join(),
onNonMatch: (string) => string,
);
// reverse words in string
return text.split(' ').reversed.join(' ');
}