CODEWITHSUNDEEP
flutterdartdart-async
maddy
maddy

Reputation: 4111

async await not working as expected, it must return me future result

My code with Future & Then works perfectly. see below:

/*main is the entry point of code*/
void main() {

var futureObject = getPostFromServer();
printPost(futureObject);

}
getPostFromServer(){

var duration = Duration(seconds : 5);
var computation = (){
return "You will get it in future" ;
};

var futureObject = Future.delayed(duration, computation);
return futureObject;

}
printPost(var futureObject){
futureObject.then(
(actualString){
print(actualString);
}

);
}
/*
OUTPUT
You will get it in future
*/

However, when I am trying the same with async & wait I am not able to get the same output. 

    Instance of '_Future<dynamic>'

Why not I am able to get future value?

/*main is the entry point of code*/
void main() {

var futureObject = getPostFromServer();
printPost(futureObject);

}
getPostFromServer() async {

var duration = Duration(seconds : 5);
var computation = (){
return "You will get it in future" ;
};

var futureObject = await Future.delayed(duration, computation);
return futureObject;

}
printPost(var futureObject){
print(futureObject);
}
/*
OUTPUT
start
Instance of '_Future<dynamic>'
end    */

Thanks

Upvotes: 0

Views: 1091

Answers (1)

Abhilash Chandran
Abhilash Chandran

Reputation: 7509

When you mark a method with async, dart will return you a Future implicitly. So if you want to use the result of this method you have to again await the result.

Below I have awaited the future and then printed it in an async method. So my rule of thumb is always await and do your functionality as you would in a sequential program. If you return a value from an async function you are telling dart that method will take time execute so wrap it in a future and return the results.

In your example getPostFromServer() acts as a mini server in you client side code and printPost() acts as sub client who should wait and then read the results. async and await are equally important in both server and client side. Only diference would be how we use it. :)

void main() {

var futureObject = getPostFromServer();
printPost(futureObject);

}
getPostFromServer() async {

var duration = Duration(seconds : 5);
var computation = (){
return "You will get it in future" ;
};

var futureObject = await Future.delayed(duration, computation);
return futureObject;

}
printPost(var futureObject) async {
 print(await futureObject);
}

Same code in dartpad:

https://dartpad.dartlang.org/59610dc768e232ac5a8e724f7fe0eee6

Upvotes: 1

Related Questions