Question 77427 in Flutter Question posted in
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How to add a map into List of maps? – Flutter

Let’s say i have this List of maps :

List values = [
  {
    'icon': FontAwesomeIcons.book,
    'title': 'A',
    'books': [
      {'author': 'Max', 'age': 30},
      {'author': 'Dani', 'age': 45}
    ]
  },
  {
    'icon': FontAwesomeIcons.book,
    'title': 'B',
    'books': [],
  }
];

How to check if this book exists to where the title ‘A’ {'author': 'Steve', 'age': 28}, and if it doesn’t exists how to add it.

Edit:

The result i want to reach is :

List values = [
      {
        'icon': FontAwesomeIcons.book,
        'title': 'A',
        'books': [
          {'author': 'Max', 'age': 30},
          {'author': 'Dani', 'age': 45},
          {'author': 'Steve', 'age': 28} 
        ]
      },
      {
        'icon': FontAwesomeIcons.book,
        'title': 'B',
        'books': [],
      }
    ];
Tags:

3

Answers


  1. 0

    You can use .firstWhere to find item, like

    final result = values.firstWhere(
  (element) => element["title"] == "A",
  orElse: () => null,
);

print(result);

if (result == null) {
  values.add({
    'icon': FontAwesomeIcons.book,
    'title': 'A',
    'books': [
      {'author': 'Max', 'age': 30},
      {'author': 'Dani', 'age': 45}
    ]
  });
}

print(values);
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  2. 0 
      
// Check by title
  final bookExcists = values.any((book) => book['title'] == 'A');
  
  if(!bookExcists){
  values.add({
    'icon': FontAwesomeIcons.book,
    'title': 'A',
    'books': [
      {'author': 'Max', 'age': 30},
      {'author': 'Dani', 'age': 45}
    ]
  });
  }
  
  print(values);
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  3. 0

    I strongly recommend using Data Models. it will make your work easier.

    class DataModel {
  String? title;
  List<Books>? books;

  DataModel({this.title, this.books});

  DataModel.fromJson(Map<String, dynamic> json) {
    title = json['title'];
    if (json['books'] != null) {
      books = <Books>[];
      json['books'].forEach((v) {
        books!.add(new Books.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['title'] = this.title;
    if (this.books != null) {
      data['books'] = this.books!.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class Books {
  String? author;
  int? age;

  Books({this.author, this.age});

  Books.fromJson(Map<String, dynamic> json) {
    author = json['author'];
    age = json['age'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['author'] = this.author;
    data['age'] = this.age;
    return data;
  }
}

    When using this model, you can easily convert and edit your data:

    List<DataModel> list = [];
  for(final item in values){
    list.add(DataModel.fromJson(item));
  }
  
  final bookExcists = list.any((book) => book.title == 'A');
  
  if(bookExcists){
    list.firstWhere((book) => book.title == 'A').books?.add(Books.fromJson({'author': 'Steve', 'age': 28}));
  }
  
  
  for(final item in list){
    print(item.toJson());
  }
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