How to perform Async await in the below code - flutter

Question

I need clarifications about how to solve the below code using async and await and future API in dart.
void main()
{
print("Program starts");
printdart(1);
print("Program finishes");
}
printdart(int temp)
{
int i;
for(i=temp;i<=1000;i++)
{
print("dart");
if(i%10==0)
{
printangular(i+1);
break;
}
}
}
printangular(int temp)
{
int i;
for(i=temp;i<=1000;i++)
{
print("angular");
if(i%10==0)
{
printdart(i+1);
break;
}
}
}
How to implement async and await in dart

Answer 1

I think you need to study more how Dart deals with Threads. I can't explain everything here, but basically Dart runs only one Thread, so all your code will just block that Thread, async awit won't help you.
Dart also have Isolates, that can run in multiple threads, but since they are very isolated, it's not easy to pass and get data from them.
Async/await works best with network requests and file access, because they block once activated, so the Thread can just ignore them for now and go back there when there's a new value. Your code in the other hand doesn't block, so you can't await for it.
There's one way though, you need to refractor your code so it will yield values, and you can async await them. In this case you need to read about Async Generators and see how they work so you can reformat your code accordingly.

Answer 2

In the code you provided, there is no waiting for the code to do some heavy process.
Below is a modified version of your code. Here, the code will wait for some time before it is called again. In the meantime rest of the code is executed.
import 'dart:async';
void main() {
print("Program starts");
printdart();
printangular();
print("Program finishes");
}
printdart() async {
int i;
for (i = 1; i <= 4; i++) {
print("dart");
await Future.delayed(const Duration(seconds: 2));
}
}
printangular() async {
int i;
for (i = 1; i <= 4; i++) {
print("angular");
await Future.delayed(const Duration(seconds: 1));
}
}
To answer your question:
async: a keyword to tell the compiler that the function will take some time to complete but in the meantime, go back and run the next part of the program and come back when this function is done.
await: this allows waiting for the process to complete before jumping to immediate next line.