Dart Cheat Sheet
Dart Cheat Sheet 1. Basic Syntax Comments // Single-line comment /* Multi-line comment */ /// Documentation comment Variables and Data Types // Type inference var name = 'Bob'; Object obj = 'Bob'; dynamic dyn = 'Bob'; // Explicit typing String name = 'Bob'; int age = 30; double height = 1.75; bool isStudent = true; List<int> numbers = [1, 2, 3]; Map<String, int> scores = {'Bob': 90, 'Alice': 95}; Constants const pi = 3.14; final currentTime = DateTime.now(); Operators // Arithmetic: +, -, *, /, ~/ (integer division), % // Increment/decrement: ++, -- // Equality and relational: ==, !=, >, <, >=, <= // Logical: &&, ||, ! // Cascade: .. // Null-aware: ??, ?. Type Casting int x = 1; double y = x.toDouble(); String s = x.toString(); 2. Control Structures Conditional Statements if (condition) { // code } else if (otherCondition) { // code } else { // code } switch (variable) { case value1: // code break; case value2: case value3: // code break; default: // code } Loops for (var i = 0; i < 5; i++) { // code } while (condition) { // code } do { // code } while (condition); for (var item in iterable) { // code } iterable.forEach((item) { // code }); 3. Functions Function Declaration and Definition int add(int a, int b) { return a + b; } // Arrow function int multiply(int a, int b) => a * b; Parameters and Return Values // Optional positional parameters String greet(String name, [String? greeting]) { greeting ??= 'Hello'; return '$greeting, $name!'; } // Named parameters void printPerson({required String name, int? age}) { print('Name: $name, Age: ${age ?? "Unknown"}'); } Anonymous Functions / Lambdas var list = ['apple', 'banana', 'cherry']; list.forEach((item) => print(item)); 4. Data Structures Lists var fruits = ['apple', 'banana', 'cherry']; fruits.add('date'); var firstFruit = fruits[0]; Maps var scores = {'Alice': 90, 'Bob': 85}; scores['Charlie'] = 95; var aliceScore = scores['Alice']; Sets var uniqueNumbers = {1, 2, 3, 4, 5}; uniqueNumbers.add(6); 5. Object-Oriented Programming Classes and Objects class Person { String name; int age; Person(this.name, this.age); void sayHello() { print('Hello, I am $name'); } } var person = Person('Alice', 30); person.sayHello(); Inheritance class Student extends Person { String school; Student(String name, int age, this.school) : super(name, age); } Interfaces and Abstract Classes abstract class Shape { double getArea(); } class Circle implements Shape { double radius; Circle(this.radius); @override double getArea() => 3.14 * radius * radius; } 6. Exception Handling try { // code that might throw an exception } on SpecificException catch (e) { // handle specific exception } catch (e) { // handle any exception } finally { // always executed } 7. File I/O import 'dart:io'; // Reading File file = File('example.txt'); String contents = await file.readAsString(); // Writing await file.writeAsString('Hello, Dart!'); // Working with directories Directory dir = Directory('path/to/directory'); await for (var entity in dir.list()) { print(entity.path); } 8. Modules and Packages // Importing import 'dart:math'; import 'package:http/http.dart' as http; // Exporting export 'src/my_module.dart'; 9. Standard Library dart:core: Built-in types, collections, and other core functionality dart:async: Asynchronous programming dart:math: Mathematical constants and functions dart:io: I/O for non-web applications dart:convert: Encoders and decoders for JSON and UTF-8 10. Asynchronous Programming Future<String> fetchData() async { // Simulating network request await Future.delayed(Duration(seconds: 2)); return 'Data'; } void main() async { var data = await fetchData(); print(data); } 11. Memory Management Dart uses automatic garbage collection 12. Important Language-Specific Features Null safety Futures and Streams for asynchronous programming Mixins for reusing code in multiple class hierarchies 13. Best Practices and Style Guide Use lowerCamelCase for variables and functions Use UpperCamelCase for classes and types Use underscores for libraries and file names Prefer using const for compile-time constants 14. Useful Resources Official Documentation: https://dart.dev/guides DartPad (Online Editor): https://dartpad.dev/ Pub.dev (Package repository): https://pub.dev/ Flutter (UI framework using Dart): https://flutter.dev/