Iterables are a fundamental concept in Dart programming, offering a powerful way to work with collections of data. They provide a lazy evaluation mechanism, allowing for efficient manipulation of sequences.

What are Iterables?

An iterable is an object that can be iterated over, meaning you can traverse its elements one by one. In Dart, the Iterable class is the base class for all iterable collections.

Key Features of Iterables

Lazy evaluation: Elements are computed only when needed
Memory efficiency: Ideal for large or infinite sequences
Chaining operations: Combine multiple operations without creating intermediate collections

Creating Iterables

Dart provides several ways to create iterables:


// From a List
Iterable<int> numbers = [1, 2, 3, 4, 5];

// Using a generator function
Iterable<int> evenNumbers = Iterable.generate(5, (index) => index * 2);

// From a Set
Set<String> fruits = {'apple', 'banana', 'orange'};
Iterable<String> fruitIterable = fruits;

Common Iterable Operations

Dart's Iterable class provides numerous methods for manipulating collections:


Iterable<int> numbers = [1, 2, 3, 4, 5];

// Filtering
var evenNumbers = numbers.where((n) => n % 2 == 0);

// Mapping
var squared = numbers.map((n) => n * n);

// Reducing
var sum = numbers.reduce((value, element) => value + element);

// Checking conditions
bool allPositive = numbers.every((n) => n > 0);
bool anyEven = numbers.any((n) => n % 2 == 0);

Iterables vs Lists

While Dart Lists are also iterable, there are key differences:

Iterables	Lists
Lazy evaluation	Eager evaluation
No random access	Random access (indexing)
Potentially infinite	Fixed size

Best Practices

Use iterables for large or infinite sequences to conserve memory
Chain operations for better readability and performance
Convert to a list only when necessary, using toList()

Related Concepts

To further enhance your understanding of Dart collections, explore these related topics:

Mastering iterables in Dart will significantly improve your ability to work with collections efficiently, leading to more performant and readable code.