What is the best way to trim a trailing character in Dart? - dart

Question

In Dart the trim(), trimLeft() and trimRight() string methods do not take a parameter to specify unwanted non-whitespace characters.
What is the best way to trim a specific character from the ends of a string in Dart?
I am using this for now, but it feels hard to remember and not very generic:
final trailing = RegExp(r"/+$");
final trimmed = "test///".replaceAll(trailing, "");
assert(trimmed == "test");

Answer 1

There is no specific functionality to trim non-whitespace from the end of a string.
Your RegExp based approach is reasonable, but can be dangerous when the character you want to remove is meaningful in a RegExp.
I'd just make my own function:
String removeTrailing(String pattern, String from) {
if (pattern.isEmpty) return from;
var i = from.length;
while (from.startsWith(pattern, i - pattern.length)) i -= pattern.length;
return from.substring(0, i);
}
Then you can use it as:
final trimmed = removeTrailing("/", "test///")
assert(trimmed == "test");
The corresponding trimLeading function would be:
String trimLeading(String pattern, String from) {
if (pattern.isEmpty) return from;
var i = 0;
while (from.startsWith(pattern, i)) i += pattern.length;
return from.substring(i);
}

Answer 2

Since the existing answer by lrn has a lot of problems - including infinite loop scenarios - I thought I'd post my version.
String trimLeft(String from, String pattern){
if( (from??'').isEmpty || (pattern??'').isEmpty || pattern.length>from.length ) return from;
while( from.startsWith(pattern) ){
from = from.substring(pattern.length);
}
return from;
}
String trimRight(String from, String pattern){
if( (from??'').isEmpty || (pattern??'').isEmpty || pattern.length>from.length ) return from;
while( from.endsWith(pattern) ){
from = from.substring(0, from.length-pattern.length);
}
return from;
}
String trim(String from, String pattern){
return trimLeft(trimRight(from, pattern), pattern);
}

Answer 3

To trim all trailing/right characters by specified characters, use the method:
class StringUtil {
static String trimLastCharacters(String srcStr, String pattern) {
if (srcStr.length > 0) {
if (srcStr.endsWith(pattern)) {
final v = srcStr.substring(0, srcStr.length - 1 - pattern.length);
return trimLastCharacters(v, pattern);
}
return srcStr;
}
return srcStr;
}
}
For example, you want to remove all 0 behind the decimals
$23.67890000
then, invoke the method
StringUtil.trimLastCharacters("$23.67890000", "0")
finally, got the output:
$23.6789