3.Dart Basic Syntax

                                          Basic  Syntax  in Dart

Dart is a modern, object-oriented language with a simple and clean syntax. Here are some basic syntax elements of Dart to get you started:

1. Entry Point

Every Dart program starts with the main function:

void main() {
  print('Hello, World!');
}

2. Variables

Variables can be declared using var, final, or const

void main() {
  var name = 'Alice';
  final age = 30; // Cannot be changed
  const pi = 3.14; // Compile-time constant
  
  print('Name: $name, Age: $age, PI: $pi');
}

Runtime Initialization: final variables are initialized at runtime. This means you can use runtime values to set them.

Compile-time Constant: A const variable is a compile-time constant. This means the value must be known and fixed at compile-time.

class CoffeeShop {
  // const is used for values that are known and fixed at compile-time
  static const int openingYear = 2020;

  // final is used for instance variables that are initialized once in the constructor
  final String name;
  final String size;
  final double price;

  // Constructor for initializing final variables
  CoffeeShop(this.name, this.size, this.price);

  void printCoffeeDetails() {
    print("Coffee: $name, Size: $size, Price: \$${price.toStringAsFixed(2)}, Opened in: $openingYear");
  }
}

void main() {
  // Creating instances of CoffeeShop class
  var coffee1 = CoffeeShop("Latte", "Medium", 3.50);
  var coffee2 = CoffeeShop("Espresso", "Small", 2.00);

  // Printing coffee details
  coffee1.printCoffeeDetails();
  coffee2.printCoffeeDetails();
}

3. Data Types

Dart supports various data types:

void main() {
int integer = 10;
double decimal = 10.5;
String text = 'Hello';
bool isTrue = true;
print('$integer, $decimal, $text, $isTrue');
}

4. Strings

Strings can be created using single or double quotes:

void main() {
 String singleQuote = 'Hello';
 String doubleQuote = "World";
 String combined = '$singleQuote $doubleQuote';
 print(combined);
}

5. Lists

Lists are ordered collections of items:

void main() {
  List<int> numbers = [1, 2, 3, 4, 5];
  print(numbers);
  print(numbers[0]); // Access first element
}

6. Maps

Maps are key-value pairs:

void main() {
  Map<String, int> ages = {
    'Alice': 25,
    'Bob': 30,
  };
 
  print(ages);
  print(ages['Alice']); // Access value by key
}

7. Functions

Functions can be declared with or without return types:

void main() {
  greet();
  print('Sum: ${add(5, 3)}');
}

void greet() {
  print('Hello!');
}

int add(int a, int b) {
  return a + b;
}

8. Control Flow Statements

If-Else

void main() {
  int number = 18;
  
  if (number > 0) {
    print('Positive');
  } else {
    print('Non-positive');
  }
}

Loops

For Loop

void main() {
  for (int i = 0; i < 5; i++) {
    print(i);
  }
}

While Loop

void main() {
  int i = 0;
  while (i < 5) {
    print(i);
    i++;
  }
}

Switch Case

void main() {
  int number = 2;
  
  switch (number) {
    case 1:
      print('One');
      break;
    case 2:
      print('Two');
      break;
    default:
      print('Other');
  }
}

9. Classes

Dart is an object-oriented language with classes and objects

void main() {
  var person = Person('Alice', 30);
  person.greet();
}

class Person {
  String name;
  int age;
  
  Person(this.name, this.age);
  
  void greet() {
    print('Hello, my name is $name and I am $age years old.');
  }
}

10. Async and Await

Dart has robust support for asynchronous programming:

import 'dart:async';

void main() async {
  print('Start');
  await fetchData();
  print('End');
}

Future<void> fetchData() async {
  await Future.delayed(Duration(seconds: 2));
  print('Data fetched');
}

These are the fundamental syntax elements to help you get started with Dart. Dart’s syntax is designed to be easy to read and write, making it a great choice for both beginners and experienced developers.