Dart Programming - Map

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The Map object is a simple key/value pair. Keys and values in a map may be of any type. A Map is a dynamic collection. In other words, Maps can grow and shrink at runtime.

Maps can be declared in two ways −

• Using Map Literals
• Using a Map constructor

Declaring a Map using Map Literals

To declare a map using map literals, you need to enclose the key-value pairs within a pair of curly brackets "{ }".

Here is its syntax −

 var identifier = { key1:value1, key2:value2 [,..,key_n:value_n] } 

Declaring a Map using a Map Constructor

To declare a Map using a Map constructor, we have two steps. First, declare the map and second, initialize the map.

The syntax to declare a map is as follows −

 var identifier = new Map() 

Now, use the following syntax to initialize the map −

 map_name[key] = value 

Example: Map Literal

 void main() { var details = {'Usrname':'tom','Password':'pass@123'}; print(details); } 

It will produce the following output −

 {Usrname: tom, Password: pass@123} 

Example: Adding Values to Map Literals at Runtime

 void main() { var details = {'Usrname':'tom','Password':'pass@123'}; details['Uid'] = 'U1oo1'; print(details); } 

It will produce the following output −

 {Usrname: tom, Password: pass@123, Uid: U1oo1} 

Example: Map Constructor

 void main() { var details = new Map(); details['Usrname'] = 'admin'; details['Password'] = 'admin@123'; print(details); } 

It will produce the following output −

 {Usrname: admin, Password: admin@123} 

Note − A map value can be any object including NULL.

Map Properties

The Map class in the dart:core package defines the following properties −

Map - Functions

Following are the commonly used functions for manipulating Maps in Dart.