To replace a substring within a string in Dart, you can use the replaceAll() method which takes two arguments: the substring to replace and the replacement string. Below are some examples:
Example 1:
String originalString = "Hello, world!";
String newString = originalString.replaceAll("world", "Dart");
print(newString); // Hello, Dart!
In the above example, we use the replaceAll() method to replace the substring "world" with "Dart" in the original string.
Example 2:
String originalString = "The quick brown fox jumps over the lazy dog.";
String newString = originalString.replaceAll("the", "A");
print(newString); // A quick brown fox jumps over A lazy dog.
In this example, we replace all occurrences of the substring "the" with the string "A" in the original string.
Example 3:
String originalString = "1243678";
String newString = originalString.replaceAll('6', '9');
print(newString); // 1243978
In this example, we use the replaceAll() method to replace the substring "6" with "9" in the original string.
Thus, using the replaceAll() method, you can easily replace substrings within strings in Dart.