Dart Cheat Sheet

Variables & Types

final label = age >= 18 ? 'adult' : 'minor';: Conditional expression
switch (n) { 1 || 2 => 'low', >= 3 && <= 9 => 'mid', _ => 'high' }: Switch expression with patterns
for (var i = 0; i < 5; i++) { }: Counting loop
for (final item in items) { }: For-in loop
while (cond) { } / do { } while (cond);: While loops

final nums = [1, 2, 3];: List
final ages = {'ada': 36};: Map
final tags = {'dart', 'flutter'};: Set
nums.map((n) => n * 2).where((n) => n > 2).toList(): Transform and filter
[...a, if (show) 4, for (final x in b) x * 2]: Spread, collection if and for

int square(int n) => n * n;: Arrow function
void greet({required String name, String greeting = 'Hi'}): Named parameters
String join(String a, [String? b]): Optional positional parameter
final double = (int n) => n * 2;: Anonymous function
extension on String { String get shout => '${toUpperCase()}!'; }: Extension

class Point { final int x, y; const Point(this.x, this.y); }: Class with a constant constructor
Point.origin() : x = 0, y = 0;: Named constructor with initializer list
class Dog extends Animal with Swimmer implements Pet: Inherit, mix in, implement
enum Size { small, medium, large }: Enum
sealed class Shape {} / final class Circle extends Shape {}: Sealed hierarchy for exhaustive switch
final (lat, lng) = (51.5, -0.1);: Record and destructuring

Future<String> load() async { ... }: Async function
final data = await load();: Wait for a future
await Future.wait([a(), b()]): Run futures concurrently
await for (final v in stream) { }: Consume a stream
try { ... } on FormatException catch (e) { ... } finally { ... }: Handle exceptions