isValidUsername method

bool isValidUsername()

Checks whether the string is a valid username.

Validation Rules:

  • Must be at least 3 characters long.
  • Can only contain letters (A-Z, a-z), numbers (0-9), and underscores (_)
  • Spaces or special characters are NOT allowed.

Returns:

  • true if the username is valid.
  • false if the username is invalid.

Example Usage:

String username1 = "user_123";
bool isValid1 = username1.isValidUsername(); // true

String username2 = "ab";
bool isValid2 = username2.isValidUsername(); // false (too short)

String username3 = "user@name";
bool isValid3 = username3.isValidUsername(); // false (contains @ symbol)

String username4 = "User_Name_99";
bool isValid4 = username4.isValidUsername(); // true

Edge Cases:

  • Usernames shorter than 3 characters are invalid.
  • Usernames with spaces or special characters (e.g., @, #, $, %) are invalid.
  • Usernames with only numbers are valid, e.g., "12345".

Implementation

bool isValidUsername() {
  return RegExp(r'^[a-zA-Z0-9_]{3,}$').hasMatch(this);
}