Say I have a string with n number of characters, but I want to trim it down to only 10 characters. (Given that at all times the string has greater that 10 characters) I don't know the contents of the string.
How to trim it in such a way?
I know how to trim it after a CERTAIN character
String s = "one.two";
//Removes everything after first '.'
String result = s.substring(0, s.indexOf('.'));
print(result);
But how to remove it after a CERTAIN NUMBER of characters?
All answers (using substring) get the first 10 UTF-16 code units, which is different than the first 10 characters because some characters consist of two code units. It is better to use the characters package:
import 'package:characters/characters.dart';
void main() {
final str = "Hello 😀 World";
print(str.substring(0, 9)); // BAD
print(str.characters.take(9)); // GOOD
}
prints
➜ dart main.dart
Hello 😀
Hello 😀 W
With substring you might even get half a character (which isn't valid):
print(str.substring(0, 7)); // BAD
print(str.characters.take(7)); // GOOD
prints:
Hello �
Hello 😀
The above examples will fail if string's length is less than the trimmed length. The below code will work with both short and long strings:
import 'dart:math';
void main() {
String s1 = 'abcdefghijklmnop';
String s2 = 'abcdef';
var trimmed = s1.substring(0, min(s1.length,10));
print(trimmed);
trimmed = s2.substring(0, min(s2.length,10));
print(trimmed);
}
NOTE:
Dart string routines operate on UTF-16 code units. For most of Latin and Cyrylic languages that is not a problem since all characters will fit into a single code unit. Yet emojis, some Asian, African and Middle-east languages might need 2 code units to encode a single character. E.g. '😊'.length will return 2 although it is a single character string. See characters package.
I think this should work.
String result = s.substring(0, 10);
To trim a String to a certain number of characters. The. code below works perfectly well:
// initialise your string here
String s = 'one.two.three.four.five';
// trim the string by getting the first 10 characters
String trimmedString = s.substring(0, 10);
// print the first ten characters of the string
print(trimmedString);
Output:
one.two.th
i hope this helps
You can do this in multiple ways.
'string'.substr(start, ?length) USE :- 'one.two.three.four.five'.substr(0, 10)'string'.substring(start, ?end) USE :- 'one.two.three.four.five'.substring(0, 10)'string'.slice(start, ?end) USE :- 'one.two.three.four.five'.slice(0, 10)To trim all trailing/right characters by specified characters, use the method:
static String trimLastCharacter(String srcStr, String pattern) {
if (srcStr.length > 0) {
if (srcStr.endsWith(pattern)) {
final v = srcStr.substring(0, srcStr.length - 1 - pattern.length);
return trimLastCharacter(v, pattern);
}
return srcStr;
}
return srcStr;
}
For example, you want to remove all 0 behind the decimals
$123.98760000
then, call it by
trimLastCharacter("$123.98760000", "0")
output:
$123.9876
It's not that hard if you understand how to work with Unicode characters properly. I won't say that this is the right way, but it works.
import 'package:sequence_processor/sequence_processor.dart';
import 'package:unicode/decomposers/canonical.dart';
import 'package:unicode/emoji/emoji.dart';
void main(List<String> args) {
var str = 'hello🇵🇬你们😀😀👨👩👦';
print('"$str"');
while (str.isNotEmpty) {
str = _removeChar(str, 1);
print('"$str"');
}
str = 'I 💗 you! ❤️🔥 ';
print('"$str"');
while (str.isNotEmpty) {
str = _removeChar(str, 1);
print('"$str"');
}
str = 'Amélie';
print('"$str"');
while (str.isNotEmpty) {
str = _removeChar(str, 1);
print('"$str"');
}
str = "Hello 😀 World";
print('"$str"');
while (str.isNotEmpty) {
str = _removeChar(str, 1);
print('"$str"');
}
}
// Should be stored in a static member for performance reasons.
final _processor = () {
final emojis = getUnicodeEmojiList();
final processor = SequenceProcessor<int, Object>();
for (final emoji in emojis) {
processor.addSequence(emoji.codePoints, emoji);
}
const decomposer = CanonicalDecomposer();
final mappingList = decomposer.getMappingList();
for (var i = 0; i < mappingList.length; i++) {
final mapping = mappingList[i];
final sequence = mapping.$2;
if (sequence.length > 1) {
if (!processor.hasSequence(sequence)) {
processor.addSequence(mapping.$2, mapping.$1);
}
}
}
return processor;
}();
String _removeChar(String text, int count) {
if (text.isEmpty) {
return '';
}
final result = _processor.process(text.runes.toList());
if (result.length < count) {
return '';
}
return result
.take(result.length - count)
.map((e) => e.data == null
? String.fromCharCode(e.element!)
: String.fromCharCodes(e.sequence!))
.join();
}
Output:
"hello🇵🇬你们😀😀👨👩👦"
"hello🇵🇬你们😀😀"
"hello🇵🇬你们😀"
"hello🇵🇬你们"
"hello🇵🇬你"
"hello🇵🇬"
"hello"
"hell"
"hel"
"he"
"h"
""
"I 💗 you! ❤️🔥 "
"I 💗 you! ❤️🔥"
"I 💗 you! "
"I 💗 you!"
"I 💗 you"
"I 💗 yo"
"I 💗 y"
"I 💗 "
"I 💗"
"I "
"I"
""
"Amélie"
"Améli"
"Amél"
"Amé"
"Am"
"A"
""
"Hello 😀 World"
"Hello 😀 Worl"
"Hello 😀 Wor"
"Hello 😀 Wo"
"Hello 😀 W"
"Hello 😀 "
"Hello 😀"
"Hello "
"Hello"
"Hell"
"Hel"
"He"
"H"
""
""
