I'm trying to write a method inside a package I'm currently developing but I got stuck trying to await the same method a second time.
This is the pseudo code for my method:
Future<MyResultClass> ErrorHandlingMethod(Future<MyResultClass> MyMethod) async {
MyResultClass result = await MyMethod;
(if result.failed && result.cause.canBeFixed){
...
...
// Do something that may cause MyMethod to complete successfully
...
...
result = await MyMethod;
}
return result;
}
MyMethod (a DIO request with a bunch of interceptors) completes but the server returns an error code, now in some cases I can fix whatever caused the problem so after doing that I want to make the same call again and return the new result.
The problem is the second time I'm awaiting MyMethod it returns the result I got the first time without making a new DIO request.
The real code is a little more complicated than this but this is the main problem I'm having right now.
Does anyone know how can I force MyMethod to be actually executed again?
Thanks in advance for your help
Related
Hey I need some help here for How to use timeouts in flutter correctly. First of all to explain what the main goal is:
I want to recive data from my Firebase RealTime Database but need to secure this request api call with an time out of 15 sec. So after 15 sec my timeout should throw an exception that will return to the Users frontend the alert for reasons of time out.
So I used the simple way to call timeouts on future functions:
This functions should only check if on some firebase node an ID is existing or not:
Inside this class where I have declared this functions I also have an instance which called : timeoutControl this is a class which contains a duration and some reasons for the exceptions.
Future<bool> isUserCheckedIn(String oid, String maybeCheckedInUserIdentifier, String onGateId) async {
try {
databaseReference = _firebaseDatabase.ref("Boarding").child(oid).child(onGateId);
final snapshot = await databaseReference.get().timeout(Duration(seconds: timeoutControl.durationForTimeOutInSec), onTimeout: () => timeoutControl.onEppTimeoutForTask());
if(snapshot.hasChild(maybeCheckedInUserIdentifier)) {
return true;
}
else {
return false;
}
}
catch (exception) {
return false;
}
}
The TimeOutClass where the instance timeoutControl comes from:
class CustomTimeouts {
int durationForTimeOutInSec = 15; // The seconds for how long to try until we throw an timeout exception
CustomTimeouts();
// TODO: Implement the exception reasons here later ...
onEppTimeoutForUpload() {
throw Exception("Some reason ...");
}
onEppTimeoutForTask() {
throw Exception("Some reason ...");
}
onEppTimeoutForDownload() {
throw Exception("Some reason ...");
}
}
So as you can see for example I tried to use this implementation above. This works fine ... sometimes I need to fight with un explain able things -_-. Let me try to introduce what in somecases are the problem:
Inside the frontend class make this call:
bool isUserCheckedIn = await service.isUserCheckedIn(placeIdentifier, userId, gateId);
Map<String, dynamic> data = {"gateIdActive" : isUserCheckedIn};
/*
The response here is an Custom transaction handler which contains an error or an returned param
etc. so this isn't relevant for you ...
*/
_gateService.updateGate(placeIdentifier, gateId, data).then((response) {
if(response.hasError()) {
setState(() {
EppDialog.showErrorToast(response.getErrorMessage()); // Shows an error message
isSendButtonDiabled = false; /*Reset buttons state*/
});
}
else {
// Create an gate process here ...
createGateEntrys(); // <-- If the closures update was successful we also handle some
// other data inside the RTDB for other reasons here ...
}
});
IMPORTANT to know for you guys is that I am gonna use the returned "boolean" value from this function call to update some other data which will be pushed and uploaded into another RTDB other node location for other reasons. And if this was also successful the application is going on to update some entrys also inside the RTDB -->createGateEntrys()<-- This function is called as the last one and is also marked as an async function and called with its closures context and no await statement.
The Data inside my Firebase RTDB:
"GateCheckIns" / "4mrithabdaofgnL39238nH" (The place identifier) / "NFdxcfadaies45a" (The Gate Identifier)/ "nHz2mhagadzadzgadHjoeua334" : 1 (as top of the key some users id who is checked in)
So on real devices this works always without any problems... But the case of an real device or simulator could not be the reason why I'am faceing with this problem now. Sometimes inside the Simulator this Function returns always false no matter if the currentUsers Identifier is inside the this child nodes or not. Therefore I realized the timeout is always called immediately so right after 1-2 sec because the exception was always one of these I was calling from my CustomTimeouts class and the function which throws the exception inside the .timeout(duration, onTimeout: () => ...) call. I couldn't figure it out because as I said on real devices I was not faceing with this problem.
Hope I was able to explain the problem it's a little bit complicated I know but for me is important that someone could explain me for what should I pay attention to if I am useing timeouts in this style etc.
( This is my first question here on StackOverFlow :) )
I'm on the way to evaluate Dart for a German company by porting various Java programs to Dart and compare and analyze the results. In the browser Dart wins hands down. For server software performance seemed to be a serious isssue (see this question of me) but that got mostly defused.
Now I'm in the area of porting some "simple" command-line tools where I did not expect any serious problems at all but there is at least one. Some of the tools do make HTTP requests to collect some data and the stand-alone Dart virtual machine only supports them in an asynchronous fashion. Looking through all I could find it does not seem to be possible to use any asynchronous call in a mostly synchronous software.
I understand that I could restructure the available synchronous software into an asynchronous one. But this would transform a well-designed piece of software into something less readable and more difficult to debug and maintain. For some software pieces this just does not make sense.
My question: Is there an (overlooked by me) way to embed an asynchronous call into a synchronously called method?
I imagine that it would not be to difficult to provide a system call, usable only from within the main thread, which just transfers the execution to the whole list of queued asynchronous function calls (without having to end the main thread first) and as soon as the last one got executed returns and continues the main thread.
Something which might look like this:
var synchFunction() {
var result;
asyncFunction().then(() { result = ...; });
resync(); // the system call to move to and wait out all async execution
return result;
}
Having such a method would simplify the lib APIs as well. Most "sync" calls could be removed because the re-synchronisation call would do the job. It seems to be such a logical idea that I still think it somehow exists and I have missed it. Or is there a serious reason why that would not work?
After thinking about the received answer from lm (see below) for two days I still do not understand why the encapsulation of an asynchronous Dart call into a synchronous one should not be possible. It is done in the "normal" synchronous programing world all the time. Usually you can wait for a resynchronization by either getting a "Done" from the asynchronous routine or if something fails continue after a timeout.
With that in mind my first proposal could be enhanced like that:
var synchFunction() {
var result;
asyncFunction()
.then(() { result = ...; })
.whenComplete(() { continueResync() }); // the "Done" message
resync(timeout); // waiting with a timeout as maximum limit
// Either we arrive here with the [result] filled in or a with a [TimeoutException].
return result;
}
The resync() does the same that would normally happen after ending the main method of an isolate, it starts executing the queued asynchronous functions (or waits for events to make them executable). As soon as it encounters a continueResync() call a flag is set which stops this asynchronous execution and resync() returns to the main thread. If no continueResync() call is encountered during the given timeout period it too aborts the asynchronous execution and leaves resync() with a TimeoutException.
For some groups of software which benefit from straight synchronous programing (not the client software and not the server software) such a feature would solve lots of problems for the programer who has to deal with asynchrounous-only libraries.
I believe that I have also found a solution for the main argument in lm's argumentation below. Therefore my question still stands with respect to this "enhanced" solution which I proposed: Is there anything which really makes it impossible to implement that in Dart?
The only time that you can wrap an async method in a synchronous one is when you don't need to get a return value.
For example if you want to disable the save button, save results to the server asynchronously and re-enable the save button when the job is done you can write it like this:
Future<bool> save() async {
// save changes async here
return true;
}
void saveClicked() {
saveButton.enabled = false;
save()
.then((success) => window.alert(success ? 'Saved' : 'Failed'))
.catchError((e) => window.alert(e))
.whenComplete(() { saveButton.enabled = true; });
}
Note that the saveClicked method is fully synchronous, but executes the save method asynchronously.
Note that if you make saveClicked async, not only do you have to call it using the async pattern, but the entire method body will run asynchronously so the save button will not be disabled when the function returns.
For completeness the async version of saveClicked looks like this:
Future<Null> saveClicked() async {
saveButton.enabled = false;
try {
bool success = await save();
window.alert(success ? 'Saved' : 'Failed');
}
catch (e) {
window.alert(e);
}
finally {
saveButton.enabled = true;
}
}
Yes, this is way late, but I think this is a cool feature new people should know about.
There is a way, but the Dart docs warn against it (and it's somehow "experimental", although the implications aren't really discussed).
The waitFor command.
You basically pass in an asynchronous function that returns a Future, an optional timeout parameter, and the waitFor function will return the result.
For example:
final int number = waitFor<int>(someAsyncThatReturnsInt);
The resync function cannot be implemented in Dart's current execution model.
Asynchronous execution is contagious. A synchronous function must return before any other asynchronous events can execute, so there is no way to synchronously wait for asynchronous execution.
Execution in Dart is single-threaded and event based. There is no way for the resync function to block without it also blocking all other execution in the same isolate, so the pending async operations will never happen.
To block the synchronous execution, and continue executing something else, you need to preserve the entire call stack up to that point, and reinstate it later when the synchronous operations have completed. If you have that functionality, then there are probably better ways to do things than Future and Stream :)
Also, waiting for "all async execution" isn't well-defined in an event based system. There might be a broadcast Stream emitting events coming in from the network, a periodic timer, or a receive port getting data from another isolate, or some other source of events that you can't wait for because they come from outside the isolate, or event the process. When the current isolate shuts down, it might send a final shut-down message to another isolate, so effectively the "async execution" isn't over until the isolate dies.
Using the async/await syntax, you won't get synchronous operation, but it will be easier to code the similar asynchronous operation:
function() async {
var result = await asyncFunction();
return result;
}
It won't wait for async operations that aren't reflected in the Future returned by asyncFunction, but that's the job of asyncFunction to not complete until its operations are complete.
Dart is inherently async. Trying to avoid asynchronity won't work out.
There are sync versions of some API calls for example in dart:io and in some situations it might seem simpler to use them instead but because there aren't sync versions for all methods/functions you can't avoid async entirely.
With the recent introduction of the async/await feature programming async become much simpler and the code looks almost like sync code (but it isn't).
If a call went async it stays async. As far as I know there is nothing you can do about it.
import 'package:synchronized_lite/synchronized_lite.dart';
import 'dart:async';
// Using Lock as a mixin to further mimic Java-style synchronized blocks
class SomeActivity with Lock {
bool _started = false;
Future<bool> start() async {
// It's correct to return a Future returned by synchronized()
return synchronized(() async {
if(_started)
return false;
// perform the start operation
await Future.delayed(Duration(seconds: 1));
print("Started");
_started = true;
return true;
});
}
Future<void> stop() async {
// It's also correct to await a synchronized() call before returning
// It's incorrect to neither await a synchronized() call nor return its Future.
await synchronized(() async {
if(!_started)
return;
// perform the stop operation`enter code here`
await Future.delayed(Duration(seconds: 1));
print("Stopped");
_started = false;
});
}
}
// Prints:
// Started
// Stopped
main() async {
var a = SomeActivity();
print("Hello");
a.start();
a.start();
a.stop();
await a.stop();
}
/*Since the Await statement can be used in only asynchronous methods. Then we do two methods.I thinking first we call the async method and then we constantly query the null result for the non-async method. Then we get a synchronized model. In this way, we will wait for the answer in the non-async method. Such a method comes to my mind. But as far as I can see, there is no escape from the async working model in flutter dart language. Need to get used to it.It may be unprofessional, but I wanted to share the solution that came to my mind. hope it helps.
Stock resultStockQueryByBarcodeAsync;
bool waitStockQueryByBarcodeAsyncCompleted = false;
Stock WaitStockQueryByBarcodeAsync(String barcode, int timeOut) {
CallStockQueryByBarcodeAsync(barcode);
var startTime = new DateTime.now();
while (!waitStockQueryByBarcodeAsyncCompleted) {
Duration difference = DateTime.now().difference(startTime);
if (difference.inMilliseconds > timeOut) {
throw TimeoutException("Timeout Exceeded");
}
//we must scope time. Because it can be enter endless loop.
}
return resultStockQueryByBarcodeAsync;
}
void CallStockQueryByBarcodeAsync(String barcode) async {
waitStockQueryByBarcodeAsyncCompleted = false;
resultStockQueryByBarcodeAsync = null;
var stock = await StockQueryByBarcodeAsync(barcode);/*your target async method*/
waitStockQueryByBarcodeAsyncCompleted = true;
resultStockQueryByBarcodeAsync = stock;
}
In my case, I had to initialize the database connection from constructor. I am pretty new in Flutter and I don't know what are the best practices right now. But, here is what I did.
class Storage {
late Database database;
Storage() {
getConnection().then((value) => database = value);
}
Future<Database> getConnection() async {
return await openDatabase('ims.db');
}
}
All I have done, is used the callback method to assign the value when the value is available.
Here's a solution based on staggering the start of the async function with start times at least 1 second apart, when calls come in almost simultaneously.
Steps:
Use the lastKnownTime to calculate the delta, where the initial value is 0
Once the delta is not some huge number, you know it's a duplicate call.
class StartConversationState extends State<StartConversationStatefulWidget> {
#override
Widget build(BuildContext context) {
_delayPush(); // this is the call that gets triggered multiple times
}
int lastKnownTime = 0;
int delayMillis = 3000;
_delayPush() async {
delayMillis += 1500;
await new Future.delayed(Duration(milliseconds: delayMillis));
int millisSinceEpoch = new DateTime.now().millisecondsSinceEpoch;
int delta = millisSinceEpoch - lastKnownTime;
// if delta is less than 10 seconds, means it was a subsequent interval
if (delta < 10000) {
print('_delayPush() , SKIPPING DUPLICATE CALL');
return;
}
// here is the logic you don't want to duplicate
// eg, insert DB record and navigate to next screen
}
I am very confused about this. I request you to clarify the concept.
Consider the following scenarios:
Case 1:
int number = 0;
void calculate() {
number = number + 2;
print(number);
}
I know this works just fine. "2" will be printed on the terminal.
But why shouldn't I use async-await here, like this:
int number = 0;
void calculate() async {
void addition() async {
number = number + 2;
}
await addition();
print(number);
}
This seems logical to me, since print(number) should wait for number = number + 2 to finish. Why isn't this necessary? How does dart know which operation to execute first?
How is it ensured that print(number) isn't executed before number = number + 2 and "0" is printed on the terminal?
Does the sequence in which we write these operations in the function matter?
Case 2:
Consider the case where I am interacting with SQFLite database and values fetched depend on each other.
Note: number1, number2, number3 will still have values before the following function is called.
void getValues() async {
void calculate1() {
number1 = await db.getNumber1(10);
}
void calculate2() {
number2 = await db.getNumber2(number1);
}
await calculate1().then((_) async {
await calculate2().then((_) async {
number3 = await db.getNumber3(number2);
});
});
}
I have a lot of these types of functions in my app and I am doing this everywhere.
I am kind of paranoid, thinking if old values of number1and number2 are taken as a parameter in getNumber2() and getNumber3() respectively, then I'll be doomed.
async/await are just syntax sugar for the underlying Future framework. 95% of the time, they will suffice, and are preferred by the style guide.
One exception is that you may have multiple futures that you want to wait until all are complete in parallel. In that case, you'll need to use Future.wait([future1, future2, future3]), which cannot be expressed using await.
Dart is executed line by line. So when the function is called calculation will be done first then it will be printed. So you will always get 2 printed
You can see it like there is one main thread in general which is the UI thread. Any operations you are writing in this thread will be performed line by line and after completely executing one line it will move to next line.
Now suppose you have something which you know that it will take time to be computed or fully executed with either a result or error. If you will write this in the main UI thread (synchronous thread) that means you're stopping the UI of the app, which in turn makes the app to crash(Application Not Responding Error) as the operating system feels that the app has frozen but as you know this is happening because of the compute you are running in the UI thread which is taking time and the UI is waiting for it to be completely executed.
So to overcome this issue we use Asynchronous methods to compute the time taking computations like getting some data from a database which will return a value or error in "future". The main UI thread doesn't waits for the asynchronous threads. If you don't have anything to show to the user until any asynchronous task is completed you place the loading indicators for the time being.
Hope this helps!
I'm on the way to evaluate Dart for a German company by porting various Java programs to Dart and compare and analyze the results. In the browser Dart wins hands down. For server software performance seemed to be a serious isssue (see this question of me) but that got mostly defused.
Now I'm in the area of porting some "simple" command-line tools where I did not expect any serious problems at all but there is at least one. Some of the tools do make HTTP requests to collect some data and the stand-alone Dart virtual machine only supports them in an asynchronous fashion. Looking through all I could find it does not seem to be possible to use any asynchronous call in a mostly synchronous software.
I understand that I could restructure the available synchronous software into an asynchronous one. But this would transform a well-designed piece of software into something less readable and more difficult to debug and maintain. For some software pieces this just does not make sense.
My question: Is there an (overlooked by me) way to embed an asynchronous call into a synchronously called method?
I imagine that it would not be to difficult to provide a system call, usable only from within the main thread, which just transfers the execution to the whole list of queued asynchronous function calls (without having to end the main thread first) and as soon as the last one got executed returns and continues the main thread.
Something which might look like this:
var synchFunction() {
var result;
asyncFunction().then(() { result = ...; });
resync(); // the system call to move to and wait out all async execution
return result;
}
Having such a method would simplify the lib APIs as well. Most "sync" calls could be removed because the re-synchronisation call would do the job. It seems to be such a logical idea that I still think it somehow exists and I have missed it. Or is there a serious reason why that would not work?
After thinking about the received answer from lm (see below) for two days I still do not understand why the encapsulation of an asynchronous Dart call into a synchronous one should not be possible. It is done in the "normal" synchronous programing world all the time. Usually you can wait for a resynchronization by either getting a "Done" from the asynchronous routine or if something fails continue after a timeout.
With that in mind my first proposal could be enhanced like that:
var synchFunction() {
var result;
asyncFunction()
.then(() { result = ...; })
.whenComplete(() { continueResync() }); // the "Done" message
resync(timeout); // waiting with a timeout as maximum limit
// Either we arrive here with the [result] filled in or a with a [TimeoutException].
return result;
}
The resync() does the same that would normally happen after ending the main method of an isolate, it starts executing the queued asynchronous functions (or waits for events to make them executable). As soon as it encounters a continueResync() call a flag is set which stops this asynchronous execution and resync() returns to the main thread. If no continueResync() call is encountered during the given timeout period it too aborts the asynchronous execution and leaves resync() with a TimeoutException.
For some groups of software which benefit from straight synchronous programing (not the client software and not the server software) such a feature would solve lots of problems for the programer who has to deal with asynchrounous-only libraries.
I believe that I have also found a solution for the main argument in lm's argumentation below. Therefore my question still stands with respect to this "enhanced" solution which I proposed: Is there anything which really makes it impossible to implement that in Dart?
The only time that you can wrap an async method in a synchronous one is when you don't need to get a return value.
For example if you want to disable the save button, save results to the server asynchronously and re-enable the save button when the job is done you can write it like this:
Future<bool> save() async {
// save changes async here
return true;
}
void saveClicked() {
saveButton.enabled = false;
save()
.then((success) => window.alert(success ? 'Saved' : 'Failed'))
.catchError((e) => window.alert(e))
.whenComplete(() { saveButton.enabled = true; });
}
Note that the saveClicked method is fully synchronous, but executes the save method asynchronously.
Note that if you make saveClicked async, not only do you have to call it using the async pattern, but the entire method body will run asynchronously so the save button will not be disabled when the function returns.
For completeness the async version of saveClicked looks like this:
Future<Null> saveClicked() async {
saveButton.enabled = false;
try {
bool success = await save();
window.alert(success ? 'Saved' : 'Failed');
}
catch (e) {
window.alert(e);
}
finally {
saveButton.enabled = true;
}
}
Yes, this is way late, but I think this is a cool feature new people should know about.
There is a way, but the Dart docs warn against it (and it's somehow "experimental", although the implications aren't really discussed).
The waitFor command.
You basically pass in an asynchronous function that returns a Future, an optional timeout parameter, and the waitFor function will return the result.
For example:
final int number = waitFor<int>(someAsyncThatReturnsInt);
The resync function cannot be implemented in Dart's current execution model.
Asynchronous execution is contagious. A synchronous function must return before any other asynchronous events can execute, so there is no way to synchronously wait for asynchronous execution.
Execution in Dart is single-threaded and event based. There is no way for the resync function to block without it also blocking all other execution in the same isolate, so the pending async operations will never happen.
To block the synchronous execution, and continue executing something else, you need to preserve the entire call stack up to that point, and reinstate it later when the synchronous operations have completed. If you have that functionality, then there are probably better ways to do things than Future and Stream :)
Also, waiting for "all async execution" isn't well-defined in an event based system. There might be a broadcast Stream emitting events coming in from the network, a periodic timer, or a receive port getting data from another isolate, or some other source of events that you can't wait for because they come from outside the isolate, or event the process. When the current isolate shuts down, it might send a final shut-down message to another isolate, so effectively the "async execution" isn't over until the isolate dies.
Using the async/await syntax, you won't get synchronous operation, but it will be easier to code the similar asynchronous operation:
function() async {
var result = await asyncFunction();
return result;
}
It won't wait for async operations that aren't reflected in the Future returned by asyncFunction, but that's the job of asyncFunction to not complete until its operations are complete.
Dart is inherently async. Trying to avoid asynchronity won't work out.
There are sync versions of some API calls for example in dart:io and in some situations it might seem simpler to use them instead but because there aren't sync versions for all methods/functions you can't avoid async entirely.
With the recent introduction of the async/await feature programming async become much simpler and the code looks almost like sync code (but it isn't).
If a call went async it stays async. As far as I know there is nothing you can do about it.
import 'package:synchronized_lite/synchronized_lite.dart';
import 'dart:async';
// Using Lock as a mixin to further mimic Java-style synchronized blocks
class SomeActivity with Lock {
bool _started = false;
Future<bool> start() async {
// It's correct to return a Future returned by synchronized()
return synchronized(() async {
if(_started)
return false;
// perform the start operation
await Future.delayed(Duration(seconds: 1));
print("Started");
_started = true;
return true;
});
}
Future<void> stop() async {
// It's also correct to await a synchronized() call before returning
// It's incorrect to neither await a synchronized() call nor return its Future.
await synchronized(() async {
if(!_started)
return;
// perform the stop operation`enter code here`
await Future.delayed(Duration(seconds: 1));
print("Stopped");
_started = false;
});
}
}
// Prints:
// Started
// Stopped
main() async {
var a = SomeActivity();
print("Hello");
a.start();
a.start();
a.stop();
await a.stop();
}
/*Since the Await statement can be used in only asynchronous methods. Then we do two methods.I thinking first we call the async method and then we constantly query the null result for the non-async method. Then we get a synchronized model. In this way, we will wait for the answer in the non-async method. Such a method comes to my mind. But as far as I can see, there is no escape from the async working model in flutter dart language. Need to get used to it.It may be unprofessional, but I wanted to share the solution that came to my mind. hope it helps.
Stock resultStockQueryByBarcodeAsync;
bool waitStockQueryByBarcodeAsyncCompleted = false;
Stock WaitStockQueryByBarcodeAsync(String barcode, int timeOut) {
CallStockQueryByBarcodeAsync(barcode);
var startTime = new DateTime.now();
while (!waitStockQueryByBarcodeAsyncCompleted) {
Duration difference = DateTime.now().difference(startTime);
if (difference.inMilliseconds > timeOut) {
throw TimeoutException("Timeout Exceeded");
}
//we must scope time. Because it can be enter endless loop.
}
return resultStockQueryByBarcodeAsync;
}
void CallStockQueryByBarcodeAsync(String barcode) async {
waitStockQueryByBarcodeAsyncCompleted = false;
resultStockQueryByBarcodeAsync = null;
var stock = await StockQueryByBarcodeAsync(barcode);/*your target async method*/
waitStockQueryByBarcodeAsyncCompleted = true;
resultStockQueryByBarcodeAsync = stock;
}
In my case, I had to initialize the database connection from constructor. I am pretty new in Flutter and I don't know what are the best practices right now. But, here is what I did.
class Storage {
late Database database;
Storage() {
getConnection().then((value) => database = value);
}
Future<Database> getConnection() async {
return await openDatabase('ims.db');
}
}
All I have done, is used the callback method to assign the value when the value is available.
Here's a solution based on staggering the start of the async function with start times at least 1 second apart, when calls come in almost simultaneously.
Steps:
Use the lastKnownTime to calculate the delta, where the initial value is 0
Once the delta is not some huge number, you know it's a duplicate call.
class StartConversationState extends State<StartConversationStatefulWidget> {
#override
Widget build(BuildContext context) {
_delayPush(); // this is the call that gets triggered multiple times
}
int lastKnownTime = 0;
int delayMillis = 3000;
_delayPush() async {
delayMillis += 1500;
await new Future.delayed(Duration(milliseconds: delayMillis));
int millisSinceEpoch = new DateTime.now().millisecondsSinceEpoch;
int delta = millisSinceEpoch - lastKnownTime;
// if delta is less than 10 seconds, means it was a subsequent interval
if (delta < 10000) {
print('_delayPush() , SKIPPING DUPLICATE CALL');
return;
}
// here is the logic you don't want to duplicate
// eg, insert DB record and navigate to next screen
}
I tried to validate 2 conditions inside eventually block... something like this
eventually(timeout(Span(26, Seconds)), interval(Span(2, Seconds))) {
response = executeSomeFunction
response should be = (true)
if (response) {
something = responseResult.get
something should be >= (10)
}
}
What am looking for is eventually should satisfy both the conditions. That is first it should check if response is true and then when response is true, it should validate the condition inside if loop.
I tried executing this but am getting error message
ambiguous reference to overloaded definition" referencing to line
"response should be = (true)"
Am not sure what I am trying to do is even possible inside eventually or not.
The problem is that you write
response should be = (true)
But actually you want to write:
response shouldBe true
In your case you make assignment of response should be: ResultOfBeWordForAny[Boolean] to the value true. Not clear what conversion here you expect.
P.S. Also write response = executeSomeFunction outside of eventually block, otherwise it could be executed multiple times.
P.P.S Moreover you don't need eventual call if you test result of your function, it's anyway in the scope. eventually isn't the best practice and used when function have some async side-effects you would like to test.