Dart List

Mastering Dart Lists: Comprehensive Guide and Examples

Introduction:

Learn everything you need to know about Dart lists with our comprehensive guide. From basic operations like creating and adding elements to advanced techniques like sorting and filtering, this lesson covers it all. Dive into Dart lists and become proficient in managing collections of data efficiently.

In Dart, a list is an ordered collection of elements that can be of any type, and it can grow dynamically. Here’s a brief overview of working with lists in Dart:

Creating a List 

You can create a list in Dart using the List class constructor or using a list literal, which is denoted by square brackets [].

dart

// Using List class constructor
List<int> numbers = List<int>();

// Using list literal
List<String> names = ['Gogo', 'Adam', 'Elin'];

Adding Elements:

You can add elements to the list using the add() method or by directly accessing the index.

dart

numbers.add(10); // Adds 10 to the end of the list
names[3] = 'Emily'; // Adds 'Emily' at index 3

Accessing Elements:

You can access elements in a list using the index. Indexing starts from 0.

dart

print(names[0]); // Output: Gogo

Iterating Through a List:

You can iterate through a list using loops like for-in or forEach().

dart

for (var name in names) {
print(name);
}

names.forEach((name) => print(name));

Length and Checking for Empty:

You can get the length of a list using the length property and check if a list is empty using the isEmpty property.

dart

print(names.length); // Output: 4
print(names.isEmpty); // Output: false

Updating elements:

You can update elements by assigning a new value to a specific index.

Slicing:

You can create a sublist by using the sublist() method.

Example:

dart

void main() {
List<int> numbers = [1, 2, 3, 4, 5];

// Add an element
numbers.add(6);

// Remove an element
numbers.remove(3);

// Update an element
numbers[0] = 10;

// Print elements
print(numbers); // Output: [10, 2, 4, 5, 6]

// Iterate through the list
for (var number in numbers) {
print(number);
}
}

This is a basic overview of working with lists in Dart. They are quite flexible and can be used in various scenarios to store and manipulate collections of data.

The Methods used with Dart list

Here are some commonly used methods for manipulating Dart lists:

add(E element):

Adds an element to the end of the list.

dart

List<int> numbers = [1, 2, 3];
numbers.add(4); // Adds 4 to the end of the list

addAll(Iterable<E> iterable):

Adds all elements of an iterable to the end of the list.
dart

List<int> numbers = [1, 2, 3];
numbers.addAll([4, 5, 6]); // Adds 4, 5, and 6 to the end of the list

remove(Object? value):

Removes the first occurrence of the specified value from the list.
dart

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

numbers.remove(3); // Removes the value 3 from the list

removeAt(int index):

Removes the element at the specified index from the list.
dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.removeAt(2); // Removes the element at index 2 (value 3) from the list

removeLast():

Removes the last element from the list.
dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.removeLast(); // Removes the last element (value 5) from the list

clear():

Removes all elements from the list.

dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.clear(); // Clears all elements from the list

indexOf(Object? element, [int start = 0]):

Returns the first index of the specified element in the list, starting the search from the optional start index.

dart

List<int> numbers = [1, 2, 3, 4, 5];
print(numbers.indexOf(3)); // Outputs: 2

contains(Object? element):

Checks if the list contains the specified element.

dart

List<int> numbers = [1, 2, 3, 4, 5];
print(numbers.contains(3)); // Outputs: true

forEach(void f(E element)):

Executes the specified function on each element of the list.
dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.forEach((number) => print(number)); // Prints each number in the list

sort([int Function(E a, E b)? compare]):

Sorts the elements of the list according to the specified comparator function.
dart

List<int> numbers = [3, 1, 5, 2, 4];
numbers.sort(); // Sorts the list in ascending order
print(numbers); // Outputs: [1, 2, 3, 4, 5]

insert(int index, E element):

Inserts the given element at the specified index in the list.
dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.insert(2, 10); // Inserts 10 at index 2
print(numbers); // Outputs: [1, 2, 10, 3, 4, 5]

insertAll(int index, Iterable<E> iterable):

Inserts all elements of the iterable at the specified index in the list.

dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.insertAll(2, [10, 11, 12]); // Inserts 10, 11, and 12 starting from index 2
print(numbers); // Outputs: [1, 2, 10, 11, 12, 3, 4, 5]

removeWhere(bool Function(E element) test):

Removes all elements that satisfy the specified condition from the list.
dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.removeWhere((number) => number % 2 == 0); // Removes even numbers
print(numbers); // Outputs: [1, 3, 5]

retainWhere(bool Function(E element) test):

Removes all elements that do not satisfy the specified condition from the list.
dart

List<int> numbers = [1, 2, 3, 4, 5];
numbers.retainWhere((number) => number % 2 == 0); // Retains only even numbers
print(numbers); // Outputs: [2, 4]

sublist(int start, [int? end]):

Returns a new list containing the elements from the start index, inclusive, to the end index, exclusive.

dart

List<int> numbers = [1, 2, 3, 4, 5];
List<int> sublist = numbers.sublist(2, 4); // Creates a sublist containing elements from index 2 to 3
print(sublist); // Outputs: [3, 4]

map<T>(T Function(E) f):

Returns a new list containing the results of applying the specified function to each element of the original list.

dart

List<int> numbers = [1, 2, 3, 4, 5];
List<String> stringNumbers = numbers.map((number) => number.toString()).toList(); // Converts each number to string
print(stringNumbers); // Outputs: ['1', '2', '3', '4', '5']

where(bool Function(E element) test):

Returns a new iterable containing only the elements of the original list that satisfy the specified condition.
dart

List<int> numbers = [1, 2, 3, 4, 5];
List<int> evenNumbers = numbers.where((number) => number % 2 == 0).toList(); // Filters out odd numbers
print(evenNumbers); // Outputs: [2, 4]

These are some additional methods you can use with Dart lists to perform various operations.

compete example for using all these methods

Here’s a comprehensive example demonstrating the usage of the previously mentioned methods with explanations:

dart

void main() {
// Creating a list of numbers
List<int> numbers = [1, 2, 3, 4, 5];
print('Original list: $numbers');

// Add an element
numbers.add(6);
print('After adding 6: $numbers');

// Add multiple elements
numbers.addAll([7, 8, 9]);
print('After adding 7, 8, and 9: $numbers');

// Insert an element at index 2
numbers.insert(2, 10);
print('After inserting 10 at index 2: $numbers');

// Insert multiple elements starting from index 5
numbers.insertAll(5, [11, 12, 13]);
print('After inserting 11, 12, and 13 starting from index 5: $numbers');

// Remove element with value 3
numbers.remove(3);
print('After removing 3: $numbers');

// Remove element at index 4
numbers.removeAt(4);
print('After removing element at index 4: $numbers');

// Remove last element
numbers.removeLast();
print('After removing last element: $numbers');

// Remove even numbers
numbers.removeWhere((number) => number % 2 == 0);
print('After removing even numbers: $numbers');

// Retain only odd numbers
numbers.retainWhere((number) => number % 2 != 0);
print('After retaining odd numbers: $numbers');

// Find index of value 5
print('Index of value 5: ${numbers.indexOf(5)}');

// Check if the list contains value 10
print('Contains 10? ${numbers.contains(10)}');

// Create a sublist containing elements from index 2 to 4
List<int> sublist = numbers.sublist(2, 5);
print('Sublist from index 2 to 4: $sublist');

// Map numbers to strings
List<String> stringNumbers = numbers.map((number) => number.toString()).toList();
print('List of string numbers: $stringNumbers');

// Filter out numbers greater than 5
List<int> filteredNumbers = numbers.where((number) => number > 5).toList();
print('Numbers greater than 5: $filteredNumbers');

// Clear the list
numbers.clear();
print('After clearing the list: $numbers');
}

Explanation:

We start by creating a list of integers numbers.
We then demonstrate various operations on the list:
Adding elements using add() and addAll().
Inserting elements using insert() and insertAll().
Removing elements using remove() and removeAt().
Removing the last element using removeLast().
Removing elements based on a condition using removeWhere().
Retaining elements based on a condition using retainWhere().
Finding the index of an element using indexOf().
Checking if the list contains a specific element using contains().
Creating a sublist using sublist().
Mapping elements to a new list using map().
Filtering elements using where().
Clearing the list using clear().
Each operation is performed on the numbers list, and the list is printed after each operation for demonstration purposes.
This example covers a wide range of list manipulation operations in Dart.

The ways to create Dart list

Let’s go through the step-by-step process of creating Dart lists with examples:

Step 1: Creating an Empty List

You can create an empty list using the List constructor or a list literal.

Example:

dart

// Using List constructor
List<int> numbers = List<int>();

// Using list literal
List<String> names = [];

Step 2: Initializing a List with Elements

You can initialize a list with elements using a list literal.

Example:

dart

List<int> numbers = [1, 2, 3, 4, 5];
List<String> names = ['Alice', 'Bob', 'Charlie'];

Step 3: Adding Elements to the List

You can add elements to the list using the add() method or by directly accessing the index.

Example:

dart

List<int> numbers = [];
numbers.add(10); // Adds 10 to the end of the list
numbers.add(20); // Adds 20 to the end of the list

List<String> names = ['Alice', 'Bob', 'Charlie'];
names[3] = 'David'; // Adds 'David' at index 3

Step 4: Concatenating Lists

You can concatenate lists using the addAll() method.

Example:

dart

List<int> numbers = [1, 2, 3];
numbers.addAll([4, 5, 6]); // Adds 4, 5, and 6 to the end of the list

Step 5: Creating a List with a Fixed Size

You can create a list with a fixed size using the List constructor with a specific length.

Example:

dart

List<int> fixedLengthList = List<int>(5); // Creates a list with a fixed size of 5

Step 6: Creating a List from an Iterable

You can create a list from an iterable using the toList() method.

Example:

dart

Set<int> uniqueNumbers = {1, 2, 3, 4, 5};
List<int> numberList = uniqueNumbers.toList(); // Creates a list from the set

Step 7: Generating a List with a Given Length

You can generate a list with a given length using the generate() method.

Example:

dart

List<int> squares = List.generate(5, (index) => (index + 1) * (index + 1)); // Generates squares of numbers from 1 to 5

These are the steps to create Dart lists along with examples illustrating each step. Lists in Dart are flexible and can be initialized, modified, and manipulated in various ways to suit your needs.

Example about ways to create dart list 

let’s create a complete example demonstrating different ways to create Dart lists along with explanations for each method:

dart

void main() {
// Step 1: Creating an Empty List
List<int> emptyList = List<int>();
print('Step 1: Creating an Empty List: $emptyList');

// Step 2: Initializing a List with Elements using a list literal
List<int> numbers = [1, 2, 3, 4, 5];
print('Step 2: Initializing a List with Elements: $numbers');

// Step 3: Adding Elements to the List
List<String> names = [];
names.add('Alice');
names.add('Bob');
names.add('Charlie');
print('Step 3: Adding Elements to the List: $names');

// Step 4: Concatenating Lists using addAll()
List<int> evenNumbers = [2, 4, 6];
List<int> oddNumbers = [1, 3, 5];
evenNumbers.addAll(oddNumbers);
print('Step 4: Concatenating Lists: $evenNumbers');

// Step 5: Creating a List with a Fixed Size
List<int> fixedLengthList = List<int>.filled(3, 0); // Creates a list with a fixed size of 3 and initializes with zeros
print('Step 5: Creating a List with a Fixed Size: $fixedLengthList');

// Step 6: Creating a List from an Iterable
Set<int> uniqueNumbers = {1, 2, 3, 4, 5};
List<int> numberList = uniqueNumbers.toList();
print('Step 6: Creating a List from an Iterable: $numberList');

// Step 7: Generating a List with a Given Length using generate()
List<int> squares = List<int>.generate(5, (index) => (index + 1) * (index + 1)); // Generates squares of numbers from 1 to 5
print('Step 7: Generating a List with a Given Length: $squares');
}

Explanation:

Creating an Empty List: We create an empty list using the List constructor without any elements inside it.

Initializing a List with Elements: We initialize a list with elements using a list literal, which directly contains the elements.

Adding Elements to the List: We create an empty list and add elements to it using the add() method.

Concatenating Lists using addAll(): We concatenate two lists by adding all elements of one list to another using the addAll() method.

Creating a List with a Fixed Size: We create a list with a fixed size using the List.filled() constructor and initialize all elements with a default value.

Creating a List from an Iterable: We convert a set of unique numbers into a list using the toList() method.

Generating a List with a Given Length using generate(): We generate a list of squares of numbers from 1 to 5 using the generate() method.

These examples demonstrate various ways to create Dart lists and illustrate their flexibility in terms of initialization and population with data.

Another example

Here’s another example demonstrating different ways to create Dart lists with a focus on generating lists:

dart

void main() {
// Step 1: Generating a List with a Given Length using List.generate()
List<int> squares = List<int>.generate(5, (index) => (index + 1) * (index + 1));
print('Step 1: Generating a List with a Given Length: $squares');

// Step 2: Generating a List of Even Numbers using List.generate()
List<int> evenNumbers = List<int>.generate(5, (index) => (index + 1) * 2);
print('Step 2: Generating a List of Even Numbers: $evenNumbers');

// Step 3: Generating a List with a Given Length using List.generate() and a custom function
List<String> names = List<String>.generate(3, (index) => 'Name ${index + 1}');
print('Step 3: Generating a List with a Given Length using a custom function: $names');

// Step 4: Generating a List of Fibonacci Sequence
List<int> fibonacci = [1, 1];
for (int i = 2; i < 10; i++) {
fibonacci.add(fibonacci[i - 1] + fibonacci[i - 2]);
}
print('Step 4: Generating a List of Fibonacci Sequence: $fibonacci');

// Step 5: Generating a List with a Pattern using List.generate()
List<int> patternList = List<int>.generate(5, (index) => index % 2 == 0 ? index : index * 2);
print('Step 5: Generating a List with a Pattern: $patternList');
}

Explanation:

Generating a List with a Given Length using List.generate(): We generate a list of squares of numbers from 1 to 5 using the generate() method. We specify the length of the list and provide a function to generate each element based on its index.

Generating a List of Even Numbers using List.generate(): Similarly, we generate a list of even numbers by multiplying the index by 2 in the generating function.

Generating a List with a Given Length using List.generate() and a custom function: We generate a list of names using a custom function inside the generate() method. The function generates names based on the index.

Generating a List of Fibonacci Sequence: We manually generate a list of Fibonacci numbers by adding the last two numbers to generate the next number in the sequence.

Generating a List with a Pattern using List.generate(): We generate a list where even indices contain the index value itself, and odd indices contain double the index value using a conditional expression inside the generating function.

These examples showcase various ways to generate lists in Dart, whether it’s based on mathematical sequences, custom functions, or specific patterns.

An application about Dart list 

Let’s create a simple Dart application that demonstrates various operations on lists, such as adding elements, removing elements, and searching for elements. I’ll provide explanations along with each part of the code.

dart

import 'dart:io'; // Importing the 'dart:io' library for input

void main() {
List<String> todoList = []; // Creating an empty list to store todo items

// Adding initial todo items
todoList.addAll(['Buy groceries', 'Clean the house', 'Finish homework']);

print('Welcome to the Todo List App!');

// Main loop of the application
while (true) {
print('\nYour Todo List:');
if (todoList.isEmpty) {
print('No items in the list.');
} else {
for (int i = 0; i < todoList.length; i++) {
print('${i + 1}. ${todoList[i]}');
}
}

// Displaying menu options
print('\nMenu:');
print('1. Add todo item');
print('2. Remove todo item');
print('3. Search for todo item');
print('4. Exit');

// Getting input for menu choice
stdout.write('Enter your choice: ');
String choice = stdin.readLineSync() ?? '';
print('');

switch (choice) {
case '1':
addTodoItem(todoList);
break;
case '2':
removeTodoItem(todoList);
break;
case '3':
searchTodoItem(todoList);
break;
case '4':
print('Exiting the Todo List App.');
return;
default:
print('Invalid choice. Please enter a number from 1 to 4.');
}
}
}

// Function to add a todo item to the list
void addTodoItem(List<String> todoList) {
stdout.write('Enter todo item: ');
String newItem = stdin.readLineSync() ?? '';
todoList.add(newItem);
print('Todo item added: $newItem');
}

// Function to remove a todo item from the list
void removeTodoItem(List<String> todoList) {
if (todoList.isEmpty) {
print('No items in the list to remove.');
return;
}

stdout.write('Enter index of item to remove: ');
int index = int.tryParse(stdin.readLineSync() ?? '') ?? -1;

if (index >= 1 && index <= todoList.length) {
String removedItem = todoList.removeAt(index - 1);
print('Todo item removed: $removedItem');
} else {
print('Invalid index. Please enter a number between 1 and ${todoList.length}.');
}
}

// Function to search for a todo item in the list
void searchTodoItem(List<String> todoList) {
stdout.write('Enter todo item to search: ');
String searchTerm = stdin.readLineSync() ?? '';

int index = todoList.indexWhere((item) => item.toLowerCase().contains(searchTerm.toLowerCase()));

if (index != -1) {
print('Todo item found at index ${index + 1}: ${todoList[index]}');
} else {
print('Todo item not found.');
}
}

Explanation:

We start by importing the dart:io library to handle input/output operations.
We define a main() function where we initialize an empty list called todoList to store todo items.
Inside the main() function, we add some initial todo items to the list.
We then enter a loop that displays the todo list and a menu of options to the .
The can choose from options to add a todo item, remove a todo item, search for a todo item, or exit the application.
Depending on the ‘s choice, we call different functions (addTodoItem, removeTodoItem, searchTodoItem) to perform the corresponding operation.
Each function interacts with the todoList and performs the required operation.
We handle edge cases such as invalid input or an empty list appropriately.
The program continues to loop until the chooses to exit the application.

Quiz about Dart lists:

Here’s a quiz about Dart lists with 15 questions, each followed by an explanation:

1-What is a Dart list?

Explanation: A Dart list is an ordered collection of elements that can be of any type and can dynamically grow or shrink in size.

2-How do you create an empty list in Dart?

Explanation: You can create an empty list in Dart using the List constructor or a list literal with empty square brackets [].

3-What method is used to add elements to a Dart list?

Explanation: You can use the add() method to add elements to a Dart list. For example, myList.add(element).

4-How do you access an element in a Dart list by its index?

Explanation: You can access an element in a Dart list by using its index. Indexing starts from 0, so the first element is at index 0, the second element at index 1, and so on.

5-Which method is used to remove the last element from a Dart list?

Explanation: The removeLast() method is used to remove the last element from a Dart list.

6-How can you check if a Dart list contains a specific element?

Explanation: You can use the contains() method to check if a Dart list contains a specific element. It returns true if the element is found and false otherwise.

7-What method is used to create a sublist from a Dart list?

Explanation: The sublist() method is used to create a sublist from a Dart list. It takes two arguments: the start index (inclusive) and the end index (exclusive).

8-How do you iterate through a Dart list using a loop?

Explanation: You can iterate through a Dart list using a for loop or a forEach() method.

9-Which method is used to sort the elements of a Dart list?

Explanation: The sort() method is used to sort the elements of a Dart list. By default, it sorts the elements in ascending order.

10-What does the addAll() method do in Dart?

Explanation: The addAll() method is used to add all elements from another iterable to a Dart list.

11-How do you clear all elements from a Dart list?

Explanation: You can use the clear() method to remove all elements from a Dart list, leaving it empty.

12-Which method is used to find the index of the first occurrence of a specific element in a Dart list?

Explanation: The indexOf() method is used to find the index of the first occurrence of a specific element in a Dart list.

13-What does the removeWhere() method do in Dart?

Explanation: The removeWhere() method removes all elements from a Dart list that satisfy a specified condition.

14-How can you create a list with a fixed size in Dart?

Explanation: You can create a list with a fixed size in Dart using the List constructor with a specific length. For example, List<int> fixedList = List<int>(5);.

15-What method is used to create a new list by applying a function to each element of an existing list?

Explanation: The map() method is used to create a new list by applying a function to each element of an existing list.

multichoice quiz with explanation

Here’s a multiple-choice quiz about Dart lists, each followed by an explanation of the correct answer:

1-What is a Dart list?

A) An unordered collection of elements.
B) A fixed-size collection of elements.
C) An ordered collection of elements.
D) A collection of unique elements.
Correct Answer: C) An ordered collection of elements.

Explanation: A Dart list is an ordered collection of elements where each element has a specific position, known as its index. This means the elements are stored in a sequence and can be accessed by their index.

2-How do you create an empty list in Dart?

A) List.empty()
B) List()
C) []
D) List.empty[]
Correct Answer: C) []

Explanation: In Dart, you can create an empty list using a list literal, which is denoted by square brackets [].

3-Which method is used to add elements to the end of a Dart list?

A) insert()
B) add()
C) push()
D) append()
Correct Answer: B) add()

Explanation: The add() method is used to add elements to the end of a Dart list. It appends the element to the end of the list.

4-How do you access the first element of a Dart list?

A) list[0]
B) list.first
C) list.getElement(0)
D) list.get(0)
Correct Answer: A) list[0]

Explanation: In Dart, you can access the elements of a list by their index. Since indexing starts from 0, list[0] gives you the first element.

5-What does the removeLast() method do in Dart?

A) Removes the last element from the list.
B) Removes the first element from the list.
C) Removes all occurrences of a specific element from the list.
D) Removes all elements from the list.
Correct Answer: A) Removes the last element from the list.

Explanation: The removeLast() method removes the last element from a Dart list and returns it. If the list is empty, it throws a StateError.

6-How can you check if a Dart list is empty?

A) list.isEmpty()
B) list.size() == 0
C) list.length == 0
D) list.empty()
Correct Answer: A) list.isEmpty()

Explanation: In Dart, you can check if a list is empty using the isEmpty() property. It returns true if the list contains no elements, otherwise false.

7-What method is used to sort the elements of a Dart list?

A) sort()
B) sorted()
C) order()
D) arrange()
Correct Answer: A) sort()

Explanation: The sort() method is used to sort the elements of a Dart list. By default, it sorts the elements in ascending order.

8-Which method is used to create a sublist from a Dart list?

A) sublist()
B) slice()
C) range()
D) subset()
Correct Answer: A) sublist()

Explanation: The sublist() method is used to create a sublist from a Dart list. It takes two arguments: the start index (inclusive) and the end index (exclusive).

9-How do you iterate through a Dart list using a loop?

A) for (var item in list)
B) forEach()
C) for (int i = 0; i < list.length; i++)
D) All of the above
Correct Answer: D) All of the above

Explanation: You can iterate through a Dart list using a for-in loop, a forEach() method, or a traditional for loop.

10-What does the addAll() method do in Dart?

A) Adds a single element to the list.
B) Adds all elements from another iterable to the list.
C) Removes all elements from the list.
D) Replaces all elements in the list with a new element.
Correct Answer: B) Adds all elements from another iterable to the list.

Explanation: The addAll() method adds all elements from another iterable to a Dart list.

11-Which method is used to remove the first occurrence of a specific element from a Dart list?

A) remove()
B) delete()
C) discard()
D) eliminate()
Correct Answer: A) remove()

Explanation: The remove() method removes the first occurrence of a specific element from a Dart list.

12-What does the removeWhere() method do in Dart?

A) Removes all elements from the list.
B) Removes the last element from the list.
C) Removes all occurrences of a specific element from the list.
D) Removes all elements that satisfy a specified condition from the list.
Correct Answer: D) Removes all elements that satisfy a specified condition from the list.

Explanation: The removeWhere() method removes all elements from a Dart list that satisfy a specified condition.

13-How can you create a list with a fixed size in Dart?

A) List.fixedSize()
B) List(length)
C) List.ofSize()
D) List(length)
Correct Answer: D) List(length)

Explanation: You can create a list with a fixed size in Dart using the List constructor with a specific length. For example, List<int> fixedList = List<int>(5);.

14-What method is used to create a new list by applying a function to each element of an existing list?

A) map()
B) apply()
C) transform()
D) convert()
Correct Answer: A) map()

Explanation: The map() method is used to create a new list by applying a function to each element of an existing list.

15-What method is used to check if a Dart list contains a specific element?

A) hasElement()
B) contains()
C) isPresent()
D) has()
Correct Answer: B) contains()

Explanation: The contains() method is used to check if a Dart list contains a specific element.