Dart - 20 - Iterables and Iterators

Iterables and Iterators in Dart Programming

Iterables and iterators are fundamental concepts in Dart that facilitate the traversal and manipulation of collections of data. They provide a way to access and work with elements in lists, sets, and other iterable structures. In this discussion, we’ll explore the significance of iterables and iterators in Dart, understand how they work, and see practical examples of their use.

Understanding Iterables

An iterable in Dart represents a collection of elements that can be iterated or looped through. Common examples of iterables include lists, sets, and maps. Iterables provide a consistent and convenient way to access elements within a collection.

Creating Iterables

In Dart, you often work with built-in iterable collections like lists and sets. These collections can be created using literals or by instantiating objects from their respective classes.

Here’s an example of creating lists and sets in Dart:


// Creating a list
var myList = [1, 2, 3, 4, 5];

// Creating a set
var mySet = {1, 2, 3, 4, 5};

Iterating Over Iterables

To process each element in an iterable, you can use loops. Dart provides various methods for iterating over iterables, including the for-in loop and the forEach method.

Here’s how to iterate over an iterable in Dart:


// Using a for-in loop
for (var element in myList) {
    print(element);
}

// Using the forEach method
mySet.forEach((element) {
    print(element);
});

Understanding Iterators

An iterator in Dart is an object associated with an iterable collection. It keeps track of the current position within the collection and provides methods for retrieving the next element. Iterators allow you to access elements one at a time and traverse through the iterable efficiently.

Obtaining an Iterator

In Dart, you can obtain an iterator for an iterable using the iterator property. This property returns an iterator object that you can use to traverse the elements of the iterable.

Here’s an example of obtaining an iterator for a list in Dart:


var myList = [1, 2, 3, 4, 5];
var myIterator = myList.iterator;

Using an Iterator

Iterators in Dart provide two main methods: moveNext() and current. The moveNext() method advances the iterator to the next element, returning true if there are more elements, or false if the end of the collection is reached. The current property retrieves the current element.

Here’s how to use an iterator in Dart:


var myList = [1, 2, 3, 4, 5];
var myIterator = myList.iterator;

while (myIterator.moveNext()) {
    print(myIterator.current);
}

Iterable and Iterator Combinations

Iterables and iterators often work together. An iterable provides access to an iterator, and you can use the iterator to traverse the elements efficiently. This combination is helpful when dealing with large collections or when you need more control over the iteration process.

Here’s an example of using an iterable with an iterator in Dart:


var myList = [1, 2, 3, 4, 5];
var myIterable = myList;
var myIterator = myIterable.iterator;

while (myIterator.moveNext()) {
    print(myIterator.current);
}

Conclusion

Iterables and iterators are essential concepts in Dart that provide a structured and efficient way to work with collections of data. Whether you’re iterating over lists, sets, or other iterable structures, understanding how to use iterables and iterators effectively is crucial for developing Dart applications. With various methods and techniques, you can efficiently access and manipulate elements within your collections.

Dart – 20 – Iterables and Iterators