Flutter Nested Object (Basics)

Question

Below is an attempted nested object.

class AppColors {
  static const light = {
    final backgroundSolid = const Color.fromRGBO(255, 255, 255, 1);
    final backgroundPrimary = const Color.fromRGBO(255, 255, 255, 0.84);
  },
  static const dark = {
      final backgroundSolid = const Color.fromRGBO(0, 0, 0, 1);
      final backgroundPrimary = const Color.fromRGBO(0, 0, 2550 0.84);
  }
}

The error is on the use of final on the first line item. What is the correct way of creating nested objects?

Hmm, do you come from JS, in which you nest object using {}?, that is equivalent to the Set data structure in Dart. Also what API/design do you want to achieve by nesting these values? Don't mind the downvote and please do ask away any doubt that you have. That's what SO is for. — croxx5f
– croxx5f, Commented Oct 22, 2021 at 15:33
Yes I would have found this very straightforward in JS. The purpose is that I can use this class as an effective data set of colors whereby I can call colors relative to theme data. Updated the question to show more detail. — Walrus
– Walrus, Commented Oct 23, 2021 at 10:24

croxx5f · Accepted Answer · 2021-10-24 20:20:12Z

1

Dart is a pretty flexible language, there is not really a correct way

You could certainly implement it using Maps, but you would lose the autocomplete and safety that a class has:

class AppColors {
//These are maps, note the `:` to separate key and values
  static const light = {
  'backgroundSolid' : const Color.fromRGBO(255, 255, 255, 1);
   'backgroundPrimary' : const Color.fromRGBO(255, 255, 255, 0.84);
};
static const dark = {
 'backgroundSolid' : const Color.fromRGBO(0, 0, 0, 1);
'backgroundPrimary' : const Color.fromRGBO(0, 0, 2550 0.84);
};
}

void main()
{
final  backgroundLight=AppColors.light['backgroundPrimary'];

}

However this is how I would code it. This way you have a class holding the attributes you need, if more are added, the dart analyzer will make you refactor the factory constructors to add/delete new fields. And the access to the properties feels quite clean too.

class AppColors {
  final Color backgroundSolid;
  final Color backgroundPrimary;

  AppColors({required this.backgroundSolid, required this.backgroundPrimary});

  factory AppColors.light()=>
      AppColors(backgroundSolid: const Color.fromRGBO(255, 255, 255, 1),
          backgroundPrimary: const Color.fromRGBO(255, 255, 255, 0.84));
  factory AppColors.dark()=>
      AppColors(backgroundSolid: const Color.fromRGBO(0, 0, 0, 1),
          backgroundPrimary: const Color.fromRGBO(0, 0, 0, 0.84));

}

void main()
{
final  backgroundLight=AppColors.light().backgroundPrimary;

}

answered Oct 24, 2021 at 20:20

croxx5f

5,8182 gold badges21 silver badges40 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Walrus Over a year ago

I implemented almost exactly this earlier today. The only difference is that I placed that I turned it around so that backgroundSolid came first and light or dark were placed in a map. This allowed me to avoid ternary operators in the main app and pass the themeMode (ie. light or dark) to App Colors. So in app I have AppColors.backgroundSolid[themeMode] where theme mode is light or dark. Thanks very much for your help, R

croxx5f Over a year ago

Glad you figured it out, and sorry for the late response.

Collectives™ on Stack Overflow

Flutter Nested Object (Basics)

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related