CODEWITHSUNDEEP
stringdartflutter
Anuran Barman
Anuran Barman

Reputation: 1676

How to replace only one character in a string in Dart?

I am trying to replace only one character in a string dart but can not find any efficient way of doing that. As string is not array in Dart I can't access the character directly by index and there is no function coming in-built which can do that. What is the efficient way of doing that?

Currently I am doing that like below:

List<String> bedStatus = currentBedStatus.split("");
   bedStatus[index]='1';
   String bedStatusFinal="";
   for(int i=0;i<bedStatus.length;i++){
      bedStatusFinal+=bedStatus[i];
   }
}

index is an int and currentBedStatus is the string I am trying to manipulate.

Upvotes: 40

Views: 53654

Answers (9)

Erlend
Erlend

Reputation: 1969

You can use String.replaceRange to replace a single character of a string given a start and end index.

The method declaration looks like this:

String replaceRange(int start, int? end, String replacement)

So given the string "hello" and you'd want to replace "e" with "a", call:

"hello".replaceRange(1, 2, "a")

So 1 is the index at "e" and 2 is the index after that and the result is "hallo".

You could make a function to replace a single character like this:

String replaceCharAt(String text, int index, String replacement) {
  return text.replaceRange(index, index + 1, replacement);
}

Upvotes: 3

Cornel
Cornel

Reputation: 188

You can also use substrings and not worry about chars. Create substrings from string and use indices.

String ourString = "OK_AY"; // original string - length of 5
String oldChar = "_"; // the character we wanna find and replace - as type string - in this case, an underscore
String newChar = "X" // the char we wanna replace underscore with
int index = ourString.indexOf(oldChar, 0); // find the index in string where our char exists (may not exist)

//some logic here to return or skip next code if char wasn't found

//oldChar found at index 0 (beginning of string)
if (index == 0) {
    ourString = newChar + ourString.substring(index+1, ourString.length);
}

//oldChar found at index 4 (end of string)
else if (index == str.length-1) {
      ourString = ourString.substring(0, index) + newChar;
}

//oldChar found anywhere else between
else {
      ourString = ourString.substring(0, index) + newChar + ourString.substring(index+1, ourString.length);
}

//done, ourString is now updated "OKXAY"

Upvotes: 0

Andre Haueisen
Andre Haueisen

Reputation: 518

Here is what you can do

  final singleChar = 'a';
  final characters = yourString.characters.toList();
  characters[index] = singleChar;
  yourString = characters.join('');

Here is how it would look like in a String extension method

  String replaceCharAt({required String char, required int index}) {
    final chars = characters.toList();
    chars[index] = char;
    return chars.join('');
  }

Upvotes: 1

game420
game420

Reputation: 51

with this line you can replace the $ symbol with a blank space ''

'${double.parse (_priced.toString (). replaceAll (' \ $ ',' ')) ?? '\ $ 0.00'}' 

String x = _with.price.toString (). ReplaceAll ('\ $', '')) ?? '\ $ 0.00',

Upvotes: 5

patrick wilfried Kamelan
patrick wilfried Kamelan

Reputation: 71

You can just use this in build function to do it.

s.replaceRange(start, end, newString)

Upvotes: 3

Sixtus Agbo
Sixtus Agbo

Reputation: 19

You can use this function, just modified Dinesh's answer

      String _replaceCharAt(
          {required String character,
          required int index,
          required String oldString}) {
        if (oldString.isEmpty) {
          return character;
        } else if (index == oldString.length) {
          return oldString.substring(0, index) + character;
        } else if (index > oldString.length) {
          throw RangeError('index value is out of range');
        }
    
        return oldString.substring(0, index) +
            character +
            oldString.substring(index + 1);
      }

Upvotes: 0

Youssef Elmoumen
Youssef Elmoumen

Reputation: 553

You can use replaceAll().

String string = 'string';
final letter='i';
final newLetter='a';
string = string.replaceAll(letter, newLetter);  // strang

Upvotes: 23

Suragch
Suragch

Reputation: 511626

You can use replaceFirst().

final myString = 'hello hello';
final replaced = myString.replaceFirst(RegExp('e'), '*');  // h*llo hello

Or if you don't want to replace the first one you can use a start index:

final myString = 'hello hello';
final startIndex = 2;
final replaced = myString.replaceFirst(RegExp('e'), '*', startIndex);  // hello h*llo

Upvotes: 23

Dinesh Balasubramanian
Dinesh Balasubramanian

Reputation: 21728

Replace at particular index:

As String in dart is immutable refer, we cannot edit something like 

stringInstance.setCharAt(index, newChar)

Efficient way to meet the requirement would be:

String hello = "hello";
String hEllo = hello.substring(0, 1) + "E" + hello.substring(2);
print(hEllo); // prints hEllo

Moving into a function:

String replaceCharAt(String oldString, int index, String newChar) {
  return oldString.substring(0, index) + newChar + oldString.substring(index + 1);
}
replaceCharAt("hello", 1, "E") //usage

Note: index in the above function is zero based.

Upvotes: 31

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