Dart - Generics

In Dart, by default collections are heterogeneous. However, by the use of generics, we can make a collection to hold homogeneous values. The use of Generics makes the use of a single compulsory data type to be held inside the collection. Such collections are called type-safe collections. By the use of generics, type safety is ensured in the Dart language.

Syntax:

Collection_name <data_type> identifier= new Collection_name<data_type> 

We can use List, Set, Map, and Queue generics to implement type safety in Dart.

Generic List

In Dart, a List is simply an ordered group of objects. A list is simply an implementation of an array.

Example:

main() {  
  List<int> listEx = [];  
  listEx.add(341);  
  listEx.add(1);  
  listEx.add(23);  
   
  // iterating across list listEx  
  for (int element in listEx) {  
     print(element);  
  }  
}

Output:

341
1
23

 Generic Set

In Dart, a Set represents a collection of objects in which each object can exist only once.

Example:

main() {  
  Set <int> SetEx = new Set <int>();  
  SetEx.add(12);  
  SetEx.add(3);  
  SetEx.add(4); 
  
  // Already added once, hence wont be added
  SetEx.add(3);  
   
  // iterating across Set SetEx  
  for (int element in SetEx) {  
     print(element);  
  }  
}

Output:

12
3
4

Generic Map

In Dart, Map is a dynamic collection of the key, value pairs.

Example:

main() {  
  
  // Creating a Map with Name and ids of students
  Map <String,int> mp={'Ankur':1,'Arnav':002,'Shivam':003};  
  print('Map :${mp}');  
}

Output:

Map :{Ankur: 1, Arnav: 2, Shivam: 3}

Generic Queue

A queue is a collection that is used when the data is to be inserted in a FIFO (First in first out) manner. In Dart, a queue can be manipulated at both ends, i.e. at the start as well as the end of the queue.

Example:

import 'dart:collection';  

main() {  
  Queue<int> q = new Queue<int>();    
  
  // Inserting at end of the queue
  q.addLast(1);  
  
  // Inserting at end of the queue
  q.addLast(2);  
  
  // Inserting at start of the queue
  q.addFirst(3);
  
  // Inserting at end of the queue  
  q.addLast(4);  
  
  // Current Queue order is 3 1 2 4.
  // Removing the first element(3) of the queue  
  q.removeFirst();  
  
  // Iterating over the queue
  for(int element in q){  
     print(element);  
  }  
}

Output:

1
2
4