Question 109368 in Json Question posted in
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Json – How can I define a Map using another Map in Flutter?

I have a Map like following:

  final Map<String, dynamic> question = {
    'rating': {
      'added': false,
    }
  };

And I want to use it inside another Map like below:

  final Map<String, dynamic> book = {
    'detail': {
      'questions': [
        question // here I need to have a list of the above Map
      ]
    }
  };

But it doesn’t work. How can I use another Map‘s definition inside a Map I am gonna define as it’s parent?

Tags:

3

Answers


  1. 0

    try to put the spread operator "…" like this:

       final Map<String, dynamic> book = {
'detail': {
  'questions': [...{question}] // here I need to have a list of the above Map
  
}};

    [EDIT]
    try this instead,it should work fine now :

     late final Map<String, dynamic> book = {
'detail': {
  'questions': [...{question}] // here I need to have a list of the above Map   
}};
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  2. 0

    The instance member ‘question’ can’t be accessed in an initializer.
    Try replacing the reference to the instance member with a different
    expression

    Use it like this:

    class _MyHomePageState extends State<MyHomePage> {
  late final Map<String, dynamic> question;
  late final Map<String, dynamic> book;

  @override
  void initState() {
    super.initState();
    question = {
      'rating': {
        'added': false,
      }
    };
    book = {
      'detail': {
        'questions': [question, question, question, question]
      }
    };
  }
...
}
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  3. 0

    I tried your code and it works just fine, but as mentioned by @Soliev, it is recommended to use classes instead of plain maps.
    Here is an example of how you can use your code with classes.
    This is a very simple example, but later on, you can research data classes, toJson, and FromJson methods, and add them to your classes if needed.

    class Question {
  final Rating rating;
  Question({
    required this.rating,
  });
}

class Rating {
  final bool added;
  Rating({
    required this.added,
  });
}

class BookDetail {
  final List<Question> questions;
  BookDetail({
    required this.questions,
  });
}

class Book {
  final BookDetail detail;
  //You can add more fields 
  //final String name
  //final String author
  Book({
    required this.detail,
  });
}
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