Dart List
last modified April 4, 2025
In Dart, List is an ordered collection of elements. It maintains insertion order and allows duplicate values. Lists are similar to arrays in other languages.
Lists in Dart can be either fixed-length or growable. Growable lists can change size dynamically. Lists are zero-indexed and support various operations.
Creating a List
There are several ways to create a List in Dart. The simplest is using list literals with square brackets.
void main() {
// Using list literal
var fruits = ['apple', 'banana', 'orange'];
print(fruits);
// Using List constructor
var numbers = List<int>.filled(3, 0);
numbers[0] = 1;
numbers[1] = 2;
numbers[2] = 3;
print(numbers);
}
The first example creates a growable list of strings. The second creates a fixed-length list initialized with zeros. We then assign values to each index.
$ dart main.dart [apple, banana, orange] [1, 2, 3]
Accessing List Elements
List elements can be accessed using index notation. Dart provides various methods for safe element access.
void main() {
var colors = ['red', 'green', 'blue', 'yellow'];
// Access by index
print(colors[0]); // red
print(colors[3]); // yellow
// Safe access with elementAt
print(colors.elementAt(2)); // blue
// First and last elements
print('First: ${colors.first}');
print('Last: ${colors.last}');
// Length
print('Length: ${colors.length}');
}
We demonstrate different ways to access list elements. elementAt is safer than [] as it throws RangeError for invalid indices. first and last are convenient.
$ dart main.dart red yellow blue First: red Last: yellow Length: 4
Adding and Removing Elements
Growable lists support dynamic addition and removal of elements. Here are common operations.
void main() {
var numbers = [1, 2, 3];
// Adding elements
numbers.add(4);
numbers.addAll([5, 6]);
numbers.insert(0, 0);
print('After adding: $numbers');
// Removing elements
numbers.remove(6);
numbers.removeAt(0);
numbers.removeLast();
print('After removing: $numbers');
// Clear all
numbers.clear();
print('After clear: $numbers');
}
add appends a single element, while addAll adds multiple. insert places an element at a specific position. Various remove methods delete elements.
$ dart main.dart After adding: [0, 1, 2, 3, 4, 5, 6] After removing: [1, 2, 3, 4] After clear: []
List Iteration
Dart provides multiple ways to iterate through list elements. Here are the most common patterns.
void main() {
var languages = ['Dart', 'Python', 'Java', 'C#'];
// for loop
print('for loop:');
for (var i = 0; i < languages.length; i++) {
print(languages[i]);
}
// for-in loop
print('\nfor-in loop:');
for (var lang in languages) {
print(lang);
}
// forEach
print('\nforEach:');
languages.forEach((lang) => print(lang));
// map
print('\nmap:');
var upper = languages.map((lang) => lang.toUpperCase());
print(upper);
}
The for loop provides index access. for-in is simpler for element access. forEach is functional style. map transforms elements to a new iterable.
$ dart main.dart for loop: Dart Python Java C# for-in loop: Dart Python Java C# forEach: Dart Python Java C# map: (DART, PYTHON, JAVA, C#)
List Manipulation
Dart lists support various manipulation operations like sorting, filtering, and slicing.
void main() {
var numbers = [5, 2, 8, 1, 7, 3, 9, 4, 6];
// Sorting
numbers.sort();
print('Sorted: $numbers');
// Reversing
var reversed = numbers.reversed.toList();
print('Reversed: $reversed');
// Filtering
var even = numbers.where((n) => n % 2 == 0).toList();
print('Even numbers: $even');
// Sublist
var middle = numbers.sublist(2, 5);
print('Middle sublist: $middle');
// Shuffling
numbers.shuffle();
print('Shuffled: $numbers');
}
sort modifies the list in place. reversed returns an iterable that needs toList. where filters elements. sublist extracts a portion. shuffle randomizes order.
$ dart main.dart Sorted: [1, 2, 3, 4, 5, 6, 7, 8, 9] Reversed: [9, 8, 7, 6, 5, 4, 3, 2, 1] Even numbers: [2, 4, 6, 8] Middle sublist: [3, 4, 5] Shuffled: [5, 9, 1, 6, 3, 8, 2, 4, 7]
Spread Operator and Collection If/For
Dart supports spread operator (...) and collection if/for in list literals.
void main() {
var list1 = [1, 2, 3];
var list2 = [4, 5, 6];
// Spread operator
var combined = [...list1, ...list2];
print('Combined: $combined');
// Collection if
var includeZero = true;
var numbers = [if (includeZero) 0, ...list1];
print('With optional zero: $numbers');
// Collection for
var squares = [for (var n in list2) n * n];
print('Squares: $squares');
}
The spread operator expands a list into individual elements. Collection if conditionally includes elements. Collection for transforms elements during list creation.
$ dart main.dart Combined: [1, 2, 3, 4, 5, 6] With optional zero: [0, 1, 2, 3] Squares: [16, 25, 36]
Best Practices
- Type Safety: Always specify list types for better code clarity.
- Growable Lists: Prefer growable lists unless fixed size is needed.
- Immutable Lists: Use List.unmodifiable for read-only lists.
- Performance: Consider LinkedList for frequent insertions/deletions.
Source
This tutorial covered Dart's List with practical examples demonstrating its key features and usage patterns.
Author
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