How to replace unicode escape character in Dart - dart

Question

I need to clean up a string that has an escape character but couldn't do so.
Here is my test code:
test('Replace unicode escape character', () {
String originalText = 'Jeremiah 52:1\\u201334';
String replacedText = originalText.replaceAll(r'\\', r'\');
expect(replacedText, 'Jeremiah 52:1\u201334');
});
It fails with an error:
Expected: 'Jeremiah 52:1–34'
Actual: 'Jeremiah 52:1\\u201334'
Which: is different.
Expected: ... miah 52:1–34
Actual: ... miah 52:1\\u201334

Answer 1

Unicode characters and escape characters aren't stored the way you write them when you wrote the string -- they are converted to their own values. This is evident when you run the following code:
print('\\u2013'.length); // Prints: 6
print('\u2013'.length); // Prints: 1
Here, what happened was: the first stored the following characters: '\', 'u', '2', '0', '1', and '3' -- while the latter stored '–' only.
Hence, your attempt to change the first by replacing two slashes \\ with one slashes \ wouldn't work, as the compiler isn't converting your unicode escape characters any longer.
That doesn't mean that you won't be able to convert your unicode codes into unicode characters though. You could use the following code:
final String str = 'Jeremiah 52:1\\u2013340';
final Pattern unicodePattern = new RegExp(r'\\u([0-9A-Fa-f]{4})');
final String newStr = str.replaceAllMapped(unicodePattern, (Match unicodeMatch) {
final int hexCode = int.parse(unicodeMatch.group(1), radix: 16);
final unicode = String.fromCharCode(hexCode);
return unicode;
});
print('Old string: $str');
print('New string: $newStr');