使用 Dart 中的 get 设置修剪 @required 变量

Question

I am trying to pass a few basic strings to a User Model and then on set the strings are trimmed, but my issue is if I make the passed variables to User @required and using the usual way of using set and get give me the error " Named optional parameters can't start with an underscore"

class User {
  String id;
  String lastName;
  String email;


  String _firstName;
  String get firstName => _firstName;
  set firstName(String name) => _firstName = name.trim();


  User({@required this.id, 
        @required this._firstName, // Error thrown here
        @required this.lastName, 
        @required this.email});
}

If I do the following I get static analysis errors on the set and get variables saying The declaration '_firstName' isn't referenced. Try removing the declaration of '_firstName' The declaration '_firstName' isn't referenced. Try removing the declaration of '_firstName'

class User {
  String id;
  String lastName;
  String email;


  String firstName;
  String get _firstName => firstName; // Static analysis error here
  set _firstName(String name) => _firstName = name.trim(); // Static analysis error here


  User({@required this.id, 
        @required this.firstName, 
        @required this.lastName, 
        @required this.email});
}

Am I using get and set wrong? Is there a better way to do this?

Answer 1

EDIT: In my opinion, in your case, there is no need to use getters and setters (see documentation :

class User {
  String id;
  String lastName;
  String email;
  String firstName;

  User({
    @required this.id,
    @required this.firstName,
    @required this.lastName,
    @required this.email,
  }) {
    firstName = firstName.trim();
  }
}

Usage:

final user = User(
    id: '1',
    firstName: 'John',
    lastName: 'Doe',
    email: 'john@doe.com',
);
// set firstName :
user.firstName = 'Jane';
// get firstName :
print(user.firstName);

Answer 2

With getters and setters you expose a way to either get/set a value to local/private object.

Something like,

String get firstname => _firstName;

set firstName => _firstName = name.trim();

From the code you've shown, if all you're trying to do, is return a trimmed value, you can do that with only getter. Your code in that case might look as follows.

class User {
  String id;
  String email;
  final String name;


  String get firstName => name.trim();
  String get lastName => name.trimLeft(); //some other calculation


  User({@required this.id, 
        @required this.name, 
        @required this.email});
}