Dart Collections

📦 Dart Collections Overview

Dart collections are data structures that store multiple values. The main types are Lists, Sets, and Maps, each serving different purposes for organizing and accessing data efficiently.


// Basic collections in Dart
List<String> fruits = ['apple', 'banana', 'orange'];
Set<int> numbers = {1, 2, 3, 4, 5};
Map<String, int> ages = {'Alice': 25, 'Bob': 30};

Types of Collections

📋

Lists

Ordered collection with duplicates

List<String> colors = ['red', 'blue', 'red'];

🎯

Sets

Unique elements, no duplicates

Set<int> uniqueNumbers = {1, 2, 3, 2}; // {1, 2, 3}

🗝️

Maps

Key-value pairs for data lookup

Map<String, int> scores = {'Alice': 95, 'Bob': 87};

🔄

Iterables

Base for all collection types

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

🔹 Creating Collections

Different ways to create and initialize collections:

void main() {
  // Lists - ordered, allow duplicates
  List<String> fruits = ['apple', 'banana', 'apple'];
  var numbers = [1, 2, 3, 4, 5];
  
  // Sets - unique elements only
  Set<String> uniqueFruits = {'apple', 'banana', 'orange'};
  var uniqueNumbers = {1, 2, 3, 2}; // Duplicate 2 is ignored
  
  // Maps - key-value pairs
  Map<String, int> studentGrades = {'Alice': 95, 'Bob': 87};
  var capitals = {'USA': 'Washington', 'France': 'Paris'};
  
  print('Fruits: $fruits');
  print('Unique numbers: $uniqueNumbers');
  print('Grades: $studentGrades');
}

Output:

Fruits: [apple, banana, apple]

Unique numbers: {1, 2, 3}

Grades: {Alice: 95, Bob: 87}

🔹 Common Collection Operations

Basic operations you can perform on collections:

void main() {
  List<int> numbers = [1, 2, 3];
  
  // Adding elements
  numbers.add(4);
  numbers.addAll([5, 6]);
  
  // Accessing elements
  print('First: ${numbers.first}');
  print('Last: ${numbers.last}');
  print('Length: ${numbers.length}');
  
  // Checking contents
  print('Contains 3: ${numbers.contains(3)}');
  print('Is empty: ${numbers.isEmpty}');
  
  // Removing elements
  numbers.remove(6);
  print('After removing 6: $numbers');
}

Output:

First: 1

Last: 6

Length: 6

Contains 3: true

Is empty: false

After removing 6: [1, 2, 3, 4, 5]

🔹 Collection Methods

Useful methods for processing collections:

void main() {
  List<int> numbers = [1, 2, 3, 4, 5];
  
  // Transform elements
  var doubled = numbers.map((n) => n * 2).toList();
  print('Doubled: $doubled');
  
  // Filter elements
  var evenNumbers = numbers.where((n) => n % 2 == 0).toList();
  print('Even numbers: $evenNumbers');
  
  // Reduce to single value
  var sum = numbers.reduce((a, b) => a + b);
  print('Sum: $sum');
  
  // Check conditions
  var hasEven = numbers.any((n) => n % 2 == 0);
  var allPositive = numbers.every((n) => n > 0);
  print('Has even: $hasEven, All positive: $allPositive');
}

Output:

Doubled: [2, 4, 6, 8, 10]

Even numbers: [2, 4]

Sum: 15

Has even: true, All positive: true