You have already read many articles on “What are extensions in Flutter.”
Here, I am providing you with a list of useful extensions that I use in my projects.
I have categorized all extensions based on types.
BuildContext extensions:
- showSnackbar — Show a snackbar with a message.
import 'package:flutter/material.dart';
extension ShowSnackbar on BuildContext {
void showSnackbar(String message) {
ScaffoldMessenger.of(this).showSnackBar(
SnackBar(
content: Text(message),
),
);
}
}
Usage:
context.showSnackbar("Hello from Snackbar!");
2. navigateToRoute — Navigate to a named route.
import 'package:flutter/material.dart';
extension NavigateToRoute on BuildContext {
void navigateToRoute(String routeName) {
Navigator.of(this).pushNamed(routeName);
}
}
Usage:
context.navigateToRoute("/details");
3. popToRoot — Pop all routes and return to the root route.
import 'package:flutter/material.dart';
extension PopToRoot on BuildContext {
void popToRoot() {
Navigator.of(this).popUntil((route) => route.isFirst);
}
}
Usage:
context.popToRoot();
4. hideKeyboard — Hide the keyboard if it’s currently displayed.
import 'package:flutter/material.dart';
extension HideKeyboard on BuildContext {
void hideKeyboard() {
FocusScope.of(this).unfocus();
}
}
Usage:
context.hideKeyboard();
5. getTheme — Get the current theme data from the Theme widget ancestor.
import 'package:flutter/material.dart';
extension GetTheme on BuildContext {
ThemeData getTheme() {
return Theme.of(this);
}
}
Usage:
ThemeData theme = context.getTheme();
6. getMediaQuery — Access the media query data.
import 'package:flutter/material.dart';
extension GetMediaQuery on BuildContext {
MediaQueryData getMediaQuery() {
return MediaQuery.of(this);
}
}
Usage:
MediaQueryData mediaQuery = context.getMediaQuery();
String extensions:
- isEmail — Check if a string is a valid email address.
extension EmailValidation on String {
bool get isEmail {
final emailRegExp = RegExp(r'^[\w-]+(\.[\w-]+)*@([\w-]+\.)+[a-zA-Z]{2,7}$');
return emailRegExp.hasMatch(this);
}
}
Usage:
String email = "example@email.com";
print(email.isEmail); // true
2. isNumeric — Check if a string represents a numeric value.
extension NumericCheck on String {
bool get isNumeric {
if (this == null) {
return false;
}
return double.tryParse(this) != null;
}
}
Usage:
String number = "123.45";
print(number.isNumeric); // true
3. capitalize — Capitalize the first letter of a string.
extension CapitalizeFirstLetter on String {
String get capitalize {
if (isEmpty) {
return this;
}
return '${this[0].toUpperCase()}${substring(1)}';
}
}
Usage:
String text = "hello world";
print(text.capitalize); // "Hello world"
4. truncate — Truncate a string to a specified length.
extension TruncateString on String {
String truncate(int maxLength) {
return (length > maxLength) ? '${substring(0, maxLength)}...' : this;
}
}
Usage:
String longText = "This is a long text that needs to be truncated.";
print(longText.truncate(20)); // "This is a long text..."
5. containsIgnoreCase — Check if a string contains another string (case-insensitive).
extension ContainsIgnoreCase on String {
bool containsIgnoreCase(String other) {
return this.toLowerCase().contains(other.toLowerCase());
}
}
Usage:
String text = "Hello, Flutter!";
print(text.containsIgnoreCase("flutter")); // true
6. removeWhitespace — Remove all whitespace characters from a string.
extension RemoveWhitespace on String {
String get removeWhitespace {
return replaceAll(RegExp(r'\s+'), '');
}
}
Usage:
String text = " Remove Whitespace ";
print(text.removeWhitespace); // "RemoveWhitespace"
7. isPalindrome — Check if a string is a palindrome.
extension PalindromeCheck on String {
bool get isPalindrome {
String cleanText = this.replaceAll(RegExp(r'[^a-zA-Z0-9]'), '').toLowerCase();
String reversedText = cleanText.split('').reversed.join('');
return cleanText == reversedText;
}
}
Usage:
String palindrome = "A man, a plan, a canal, Panama";
print(palindrome.isPalindrome); // true
8. words — Split a string into a list of words.
extension WordsSplitter on String {
List<String> get words {
return split(RegExp(r'\s+'));
}
}
Usage:
String text = "Split this text into words";
print(text.words); // ["Split", "this", "text", "into", "words"]
9. replaceAllIgnoreCase — Replace all occurrences of a substring (case-insensitive).
extension ReplaceAllIgnoreCase on String {
String replaceAllIgnoreCase(String from, String to) {
return replaceAll(RegExp(from, caseSensitive: false), to);
}
}
Usage:
String text = "Hello, world! Hello, Flutter!";
print(text.replaceAllIgnoreCase("hello", "hi")); // "Hi, world! Hi, Flutter!"
10. isAlphanumeric — Check if a string contains only alphanumeric characters.
extension AlphanumericCheck on String {
bool get isAlphanumeric {
return RegExp(r'^[a-zA-Z0-9]+$').hasMatch(this);
}
}
Usage:
String alphanumeric = "Hello123";
print(alphanumeric.isAlphanumeric); // true
Int extensions:
- isPrime — Check if an integer is a prime number.
extension PrimeCheck on int {
bool get isPrime {
if (this <= 1) return false;
if (this <= 3) return true;
if (this % 2 == 0 || this % 3 == 0) return false;
int i = 5;
while (i * i <= this) {
if (this % i == 0 || this % (i + 2) == 0) return false;
i += 6;
}
return true;
}
}
Usage:
int number = 17;
print(number.isPrime); // true
2. factorial — Calculate the factorial of an integer.
extension Factorial on int {
int get factorial {
if (this == 0) return 1;
int result = 1;
for (int i = 1; i <= this; i++) {
result *= i;
}
return result;
}
}
Usage:
int n = 5;
print(n.factorial); // 120
3. toBinary and toHex — Convert an integer to a binary or hexadecimal string.
extension IntToBinaryHex on int {
String get toBinary => this.toRadixString(2);
String get toHex => this.toRadixString(16);
}
Usage:
int number = 42;
print(number.toBinary); // "101010"
print(number.toHex); // "2a"
4. divisors — Get a list of divisors of an integer.
extension Divisors on int {
List<int> get divisors {
List<int> result = [];
for (int i = 1; i <= this; i++) {
if (this % i == 0) {
result.add(i);
}
}
return result;
}
}
Usage:
int number = 12;
print(number.divisors); // [1, 2, 3, 4, 6, 12]
5. isPerfect — Check if an integer is a perfect number.
extension PerfectNumberCheck on int {
bool get isPerfect {
List<int> divisors = this.divisors;
int sum = divisors.fold(0, (a, b) => a + b) - this;
return sum == this;
}
}
Usage:
int perfectNumber = 28;
print(perfectNumber.isPerfect); // true
6. isPowerOfTwo — Check if an integer is a power of two.
extension PowerOfTwoCheck on int {
bool get isPowerOfTwo {
return (this != 0) && ((this & (this - 1)) == 0);
}
}
Usage :
int number = 16;
print(number.isPowerOfTwo); // true
7. nearestPowerOfTwo — Find the nearest power of two greater than or equal to the integer.
extension NearestPowerOfTwo on int {
int get nearestPowerOfTwo {
int result = 1;
while (result < this) {
result *= 2;
}
return result;
}
}
Usage:
int number = 12;
print(number.nearestPowerOfTwo); // 16
8. toOrdinal — Convert an integer to its ordinal form (e.g., 1st, 2nd, 3rd).
extension ToOrdinal on int {
String get toOrdinal {
if (this % 100 >= 11 && this % 100 <= 13) {
return '${this}th';
}
switch (this % 10) {
case 1:
return '${this}st';
case 2:
return '${this}nd';
case 3:
return '${this}rd';
default:
return '${this}th';
}
}
}
Usage:
int number = 23;
print(number.toOrdinal); // "23rd"
9. digitsSum — Calculate the sum of the digits of an integer.
extension DigitsSum on int {
int get digitsSum {
int sum = 0;
int number = this.abs();
while (number > 0) {
sum += number % 10;
number ~/= 10;
}
return sum;
}
}
Usage:
int number = 12345;
print(number.digitsSum); // 15
10. toWords — Convert an integer to its word representation.
extension IntToWords on int {
String get toWords {
final List<String> units = [
'', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'
];
final List<String> teens = [
'ten', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'
];
final List<String> tens = [
'', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'
];
String convertToWords(int number) {
if (number < 10) {
return units[number];
} else if (number < 20) {
return teens[number - 10];
} else if (number < 100) {
return '${tens[number ~/ 10]} ${units[number % 10]}'.trim();
} else if (number < 1000) {
return '${units[number ~/ 100]} hundred ${convertToWords(number % 100)}'.trim();
}
return 'Number out of range';
}
return convertToWords(this);
}
}
Usage:
int number = 123;
print(number.toWords); // "one hundred twenty three"
List extensions:
- groupBy — Group a list of objects by a specified key.
extension GroupBy<T, K> on List<T> {
Map<K, List<T>> groupBy(K Function(T) keySelector) {
final result = <K, List<T>>{};
for (var item in this) {
final key = keySelector(item);
result[key] ??= [];
result[key].add(item);
}
return result;
}
}
Usage:
class Person {
final String name;
final int age;
Person(this.name, this.age);
}
List<Person> people = [Person('Alice', 25), Person('Bob', 30), Person('Alice', 28)];
final grouped = people.groupBy((person) => person.name);
print(grouped);
// Output: {Alice: [Person{name: Alice, age: 25}, Person{name: Alice, age: 28}], Bob: [Person{name: Bob, age: 30}]}
2. average — Calculate the average of a list of numeric values.
extension AverageList<T extends num> on List<T> {
double get average {
if (isEmpty) return null;
final sum = this.fold(0, (a, b) => a + b);
return sum / length;
}
}
Usage:
List<double> values = [1.0, 2.5, 3.0, 4.5];
double avg = values.average;
print(avg); // 2.75
3. rotate — Rotate the elements of a list to the right by a specified number of positions.
extension RotateList<T> on List<T> {
List<T> rotate(int positions) {
final n = this.length;
final List<T> result = List<T>.filled(n, null, growable: false);
for (var i = 0; i < n; i++) {
result[(i + positions) % n] = this[i];
}
return result;
}
}
Usage:
List<int> numbers = [1, 2, 3, 4, 5];
List<int> rotated = numbers.rotate(2);
print(rotated); // [4, 5, 1, 2, 3] (rotated 2 positions to the right)
4. distinctBy — Remove duplicates from a list based on a specified key.
extension DistinctBy<T, K> on List<T> {
List<T> distinctBy(K Function(T) keySelector) {
final Set<K> seenKeys = {};
final List<T> result = [];
for (var item in this) {
final key = keySelector(item);
if (!seenKeys.contains(key)) {
seenKeys.add(key);
result.add(item);
}
}
return result;
}
}
Usage:
class Fruit {
final String name;
final String color;
Fruit(this.name, this.color);
}
List<Fruit> fruits = [Fruit('Apple', 'Red'), Fruit('Banana', 'Yellow'), Fruit('Apple', 'Green')];
final distinctFruits = fruits.distinctBy((fruit) => fruit.name);
print(distinctFruits);
// Output: [Fruit{name: Apple, color: Red}, Fruit{name: Banana, color: Yellow}]
5. interleave — Interleave the elements of two lists.
extension InterleaveLists<T> on List<T> {
List<T> interleave(List<T> other) {
final List<T> result = [];
final minLength = math.min(this.length, other.length);
for (var i = 0; i < minLength; i++) {
result.add(this[i]);
result.add(other[i]);
}
result.addAll(this.sublist(minLength));
result.addAll(other.sublist(minLength));
return result;
}
}
Usage:
List<int> list1 = [1, 3, 5];
List<int> list2 = [2, 4, 6];
List<int> interleaved = list1.interleave(list2);
print(interleaved); // [1, 2, 3, 4, 5, 6]
6. flatten — Flatten a list of lists into a single list.
extension FlattenLists<T> on List<List<T>> {
List<T> flatten() {
return this.fold([], (result, list) => result..addAll(list));
}
}
Usage:
List<List<int>> nestedList = [[1, 2], [3, 4], [5, 6]];
List<int> flatList = nestedList.flatten();
print(flatList); // [1, 2, 3, 4, 5, 6]
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