Dart| Flutter How to: Create an Empty Map

Dart| Flutter How to: Create an Empty Map

This tutorial shows multiple ways to create an empty Map in Dart or Flutter

An empty Map is a Map data structure that lacks a key and value pair of elements, and a Map has a length of zero.

In Flutter, an API or service method may return an empty Map instead of a null to improve null safety handling.

How to create an Empty Map in Flutter or dart?

An empty Map can be created in multiple ways.

  • using type and brackets

You can create a variable for any class using type and brackets() in dart

  Map map = Map();
  print(map.length); //0
  print(map.runtimeType); //JsLinkedHashMap<dynamic, dynamic>

or you can use the new keyword to create a variable for the map

  Map map = new Map();
  print(map.length); //0
  print(map.runtimeType); //JsLinkedHashMap<dynamic, dynamic>

The above codes create an empty map and return Map. length as zero(0)

It is an empty map without type safety and the default type is Map<dynamic, dynamic>.

How do you create a typed Map?

  Map<String,String> map = Map<String,String>();
  print(map.length); //0
  print(map.runtimeType); //JsLinkedHashMap<String, String>
  • using empty literal syntax

Create a variable and assign the with empty literal using [] syntax.

  Map map = {};
  print(map.length); //0
  print(map.runtimeType); //JsLinkedHashMap<dynamic, dynamic>
}

To create a typed version of the empty literal syntax This creates an empty array typed map without elements.

  Map<int,String> map = <int,String>{};
  print(map.length); //0
  print(map.runtimeType); //JsLinkedHashMap<int, String>

or you can also use empty literal without type, but the variable type is typed.

  Map<int,String> map = {};
  print(map.length); //0
  print(map.runtimeType); //JsLinkedHashMap<dynamic, dynamic>

How to Create an Empty Map of objects in a flutter

The fourth way is, Create an Empty Object Map

Here is an example code for multiple ways to create a Map of objects create a class of employees and create a Map empty object using var emps = <int, Employee>[];

class Employee {
  final int id;
  final String name;
  final int salary;
  final DateTime joinDate;

  Employee(this.id, this.name, this.salary, this.joinDate);
}

void main() {
  Map<int, Employee> emps1 = new Map<int, Employee>();
  print(emps1.length); //0
  print(emps1.runtimeType); //JsLinkedHashMap<dynamic, dynamic>

  Map<int, Employee> emps2 = <int, Employee>{};
  print(emps2.length); //0
  print(emps2.runtimeType); //JsLinkedHashMap<int, Employee>

  Map<int, Employee> emps3 = {};
  print(emps3.length); //0
  print(emps3.runtimeType); //JsLinkedHashMap<int, Employee>
}

Conclusion

This tutorial explains multiple ways to create an empty Map with int, string, and objects.