Dart Programming Language Cheatsheet – A Complete Guide
Dart is a modern, fast, and expressive programming language designed by Google. It is best known today as the core language behind Flutter, enabling developers to build cross-platform applications for Android, iOS, Web, Desktop, and Embedded systems—all from a single codebase. While Dart is easy to pick up, having a quick reference guide or “cheatsheet” helps developers write clean, efficient, and consistent code.
This comprehensive cheatsheet offers everything you need to get started with Dart—covering syntax, variables, data types, functions, classes, async programming, collections, and more. Whether you're a beginner or brushing up on essential concepts, this Dart cheatsheet will act as your go-to quick reference.
1. Introduction to Dart
Dart is an object-oriented, statically typed language with a clean syntax. It supports:
- AOT (Ahead-of-Time) compilation for fast, native apps.
- JIT (Just-in-Time) compilation for fast development cycles with hot reload.
- Sound type system, meaning variable types are known at compile time.
- Asynchronous programming, making it ideal for UI and event-driven apps.
2. Basic Syntax Cheatsheet
2.1 Main Function
Every Dart application starts with the main() method.
void main() {
print("Hello, Dart!");
}
2.2 Comments
Dart supports single, multi-line, and documentation comments:
// Single-line comment
/* Multi-line
comment */
/** Documentation comment */
3. Variables and Data Types
3.1 Declaring Variables
var name = "Dart"; // Type inferred
String language = "Dart";
int age = 10;
double rating = 4.8;
bool isOpen = true;
3.2 Final and Const
final city = "Mumbai"; // Runtime constant
const PI = 3.14; // Compile-time constant
3.3 Nullable and Non-Nullable Types
int a = 10; // Non-nullable
int? b; // Nullable
4. Operators Cheatsheet
4.1 Arithmetic Operators
+ - * / % ~/
4.2 Assignment Operators
= += -= *= /= %=
4.3 Comparison Operators
== != > < >= <=
4.4 Logical Operators
&& || !
4.5 Type Test Operators
is is! as
Example:
if (name is String) {
print("Name is a string");
}
5. Control Flow Statements
5.1 If–Else
if (age > 18) {
print("Adult");
} else {
print("Minor");
}
5.2 Switch Case
switch (day) {
case "Mon":
print("Start of week");
break;
default:
print("Other day");
}
5.3 Loops
For Loop
for (int i = 0; i < 5; i++) {
print(i);
}
While Loop
while (count < 5) {
count++;
}
Do-While Loop
do {
print("Running...");
} while (isRunning);
6. Functions Cheatsheet
6.1 Function Declaration
void greet() {
print("Hello!");
}
6.2 Function With Return Type
int add(int a, int b) {
return a + b;
}
6.3 Arrow Functions
int square(int n) => n * n;
6.4 Optional Parameters
Optional Positional
void info(String name, [String? city]) {}
Named Optional
void details({String? name, int? age}) {}
Named Required
void register({required String email, required String password}) {}
7. Collections Cheatsheet
Dart has powerful collection types.
7.1 Lists
List<int> nums = [1, 2, 3];
nums.add(4);
Constant list:
const fixed = [1, 2, 3];
7.2 Sets
Set<String> fruits = {"Apple", "Banana"};
fruits.add("Mango");
7.3 Maps
Map<String, int> ages = {
"John": 25,
"Rita": 30
};
print(ages["John"]);
7.4 Spread Operator
var list1 = [1, 2];
var list2 = [...list1, 3, 4];
7.5 Null-Aware Spread
List<int>? items;
var newList = [...?items, 10];
8. String Cheatsheet
8.1 Multi-Line Strings
var text = '''
This is a
multi-line string.
''';
8.2 String Interpolation
print("Name: $name, Age: ${age + 1}");
8.3 Common String Methods
lengthtoUpperCase()toLowerCase()contains()trim()split()
Example:
print(name.toUpperCase());
L9. Classes and Objects
9.1 Basic Class
class Person {
String name;
int age;
Person(this.name, this.age);
void show() {
print("$name is $age years old");
}
}
9.2 Named Constructors
class Point {
int x, y;
Point.origin() : x = 0, y = 0;
}
9.3 Inheritance
class Animal {
void speak() => print("Animal sound");
}
class Dog extends Animal {
@override
void speak() => print("Bark!");
}
9.4 Abstract Classes
abstract class Shape {
void draw();
}
9.5 Mixins
mixin Fly {
void fly() => print("Flying!");
}
class Bird with Fly {}
10. Async and Await Cheatsheet
Dart is built with asynchronous programming at its core.
10.1 Future Example
Future<String> fetchData() async {
return "Data loaded";
}
10.2 Using Async/Await
void main() async {
var data = await fetchData();
print(data);
}
10.3 Streams
Stream<int> numbers() async* {
for (int i = 1; i <= 5; i++) {
yield i;
}
}
11. Exception Handling
Try–Catch–Finally
try {
var result = 10 ~/ 0;
} catch (e) {
print("Error: $e");
} finally {
print("Done");
}
12. Important Dart Keywords
Some essential keywords include:
| Keyword | Purpose |
|---|---|
var |
Type inference |
final |
Runtime constant |
const |
Compile-time constant |
late |
Initialize later |
async |
Asynchronous function |
await |
Wait for Future |
yield |
Produce stream values |
enum |
Enum types |
13. Dart Tips and Best Practices
13.1 Prefer final over var
Use final to avoid unintentional reassignment.
13.2 Use Meaningful Variable Names
Improves code readability.
13.3 Use Null-Aware Operators
E.g., ??, ??=, ?.
var value = name ?? "Guest";
13.4 Always Handle Errors
Use try-catch around risky code.
13.5 Write Clean Classes
Keep methods short and maintain encapsulation.
14. Conclusion
This Dart cheatsheet provides a complete reference to help developers quickly recall essential Dart syntax, concepts, and patterns. Whether you're building mobile apps with Flutter or writing standalone Dart programs, having a compact guide like this makes coding smoother and faster. From basic syntax to classes, async programming, and collections, this cheatsheet equips you with the core knowledge needed for everyday Dart development.
If you continue practicing these concepts and writing small programs, mastering Dart becomes not only easier but enjoyable. Use this guide as your handy companion whenever you're working with Dart, and you’ll see your productivity and confidence continue to grow.
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