Flutter/Dart: get and set with private variables

Question

if I read that setters and getters have to be explicity developed in Dart only when you want to do something more than only retrieve those values. But if I have private variables, like:

Class User {
  User _user;
  String _password;
}

How can I access to those private variables? Even if I implement the set password like

 set password(String value) => _password = value;

It will of course give me an "error".

Solution 1

If you want public getter/setter what's the point of having private variable for that?

Just make it a public variable and be done.

If you insist having a private variable with public access, then you still need to add the getter and setter.

Solution 2

Private variable is import due to some reasons, If you conditionally set or get your Class property values then setter and getter is important on private variables. Example given below:

   class User {

       int _id;
       String _firstName;
       String _password;

      int get id => _id;

      set id(int value) {
        _id = value;
      }

      String get firstName => _firstName;

      set firstName(String value) {
        if(value.length > 7)
           _firstName = value;
      }

      String get password => _password;

      set password(String value) {
         if(some condition against this value like password)
            _password = value;
      }
   }

Note: you can set condition in getter like setter that I have given in above example.

Comments

[Afinas EM]

You should have to use the getter as well. In the android studio, you can simply generate these on right-clicking the code and taking the generate method (alt + insert).

[Günter Zöchbauer]

No worries. Once you know it many things might look stupid in hindsight :D

[Rémi Rousselet]

It has some uses! RenderBoxes use it a lot for things like markNeedsLayout/markNeedsPaint

[Günter Zöchbauer]

@RémiRousselet not sure what you mean. markNeedsLayout and markNeedsPaint are methods github.com/flutter/flutter/blob/…, github.com/flutter/flutter/blob/…

[Rémi Rousselet]

Renderobjects has private variable with public getter/setter where the setter call these markNeedsLayout/Paint

[Rémi Rousselet]

Example: github.com/flutter/flutter/blob/…

[Günter Zöchbauer]

I don't see how this is related to the question. Of course if you want to do additional work when a property is changed, you need a setter. That's the main purpose they exist. But there is no need to use a getter/setter if all they do is returning or updating the private property. Instead just make the property public.

[PhillipJacobs]

LOL wait. How is it useless ? In getters and setters you can perform operations on the value before setting it. Same with getter. No ?