Dart| Flutter How to: String replace method

The string is an immutable class. There is no method such as setCharAt() with an index like in java.

We can do multiple ways to replace a character or substring in a String

String replace a letter using substring in dart example

This example, Replaces the one the character with a new character in a given string.

str.substring(0, 2) returns the substring with the start and end index. str.substring(3): returns the substring start index to the remaining string

Here is an example to replace a letter from a string of characters

void main() {
  var str = "welcome john";
  print(str); //welcome john

  str = str.substring(0, 2) + "L" + str.substring(3);
  print(str);//weLcome john

}

Output:

welcome john
weLcome john

String replace a letter using replaceAll in dart example

This example uses the String replaceAll method replaces the substring

String replaceAll(Pattern from, String replace)

from string is a pattern that replaces the replace string.

It returns the new string

Here is an example

void main() {
  var str = "welcome john";
  print(str); //welcome john

  str = str.replaceAll("j", "k");

  print(str); //welcome kohn
}

Output:

welcome john
welcome kohn

String replaces a substring with replaceFirst

It is using replaceFirst with a regular expression

void main() {
  var str = "welcome john";
  print(str); //welcome john

  str = str.replaceFirst(RegExp('h'), "n");

  print(str); //welcome jonn
}

Output:

welcome john
welcome jonn

Conclusion

Learn multiple ways to replace a letter or character or substring in a string