Dart Programming - Collection

Dart, unlike other programming languages, doesn’t support arrays. Dart collections can be used to replicate data structures like an array. The dart:core library and other classes enable Collection support in Dart scripts.

Dart collections can be basically classified as −

Sr.No	Dart collection & Description
1	List A List is simply an ordered group of objects. The dart:core library provides the List class that enables creation and manipulation of lists. Fixed Length List − The list’s length cannot change at run-time. Growable List − The list’s length can change at run-time.
2	Set Set represents a collection of objects in which each object can occur only once. The dart:core library provides the Set class to implement the same.
3	Maps 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. The Map class in the dart:core library provides support for the same.
4	Queue A Queue is a collection that can be manipulated at both ends. Queues are useful when you want to build a first-in, first-out collection. Simply put, a queue inserts data from one end and deletes from another end. The values are removed / read in the order of their insertion.

Iterating Collections

The Iterator class from the dart:core library enables easy collection traversal. Every collection has an iterator property. This property returns an iterator that points to the objects in the collection.

Example

The following example illustrates traversing a collection using an iterator object.

Live Demo

import 'dart:collection'; 
void main() { 
   Queue numQ = new Queue(); 
   numQ.addAll([100,200,300]);  
   Iterator i= numQ.iterator; 
   
   while(i.moveNext()) { 
      print(i.current); 
   } 
}

The moveNext() function returns a Boolean value indicating whether there is a subsequent entry. The current property of the iterator object returns the value of the object that the iterator currently points to.

This program should produce the following output −

100 
200 
300