Basic Concept of Asynchronous programming

Concept of Asynchronous Code

A Simple Synchronous Code :

void main() {
  
  // Synchronous Code 
  print("test1");
  
  
  
  for (int i = 0; i < 5; i++) {
    print('hello ${i + 1}');
  }
  
  
 
  
  testfunction();
  
  print("test3");
  
  
}


 void testfunction(){
    
   print("test2");
    
  }

Dart is Single Threaded Note: There is a concept called "isolates" in dart which you can use to emulate multithreading

Couple of asynchronous processes :

• Fetching data over a network

• Writing to a database

• Reading data from a file

Event Loop

Futures & Callbacks

"Callbacks" are special types of functions which gets executed when the asynchronous process is done Note: Callbacks are not only used in asynchronous process , they are used in functional programming too .

First Tab

void main() {
  // Futures

  print(" Start fetching images");

  getData();

  print("Loading Images");
}

void getData() {
  //callback

  Future.delayed(Duration(seconds: 5), () {
    // Logic
    print(" Image Fetched !!!!!");
  });
}

Second Tab

import "dart:html";

void main() {
  // Futures

  print("A");

  var result =
      HttpRequest.getString('https://jsonplaceholder.typicode.com/todos/1');

  print(result);

  print("B");
}

Three state of Future

All future start with an uncompleted state . After the asynchronous process is done it either resolves into "Completed with Data" or "Completed with Error"

Future