I have a function in Flex which has three function in it.
public function update():void
{
A(); \\Dispatches a event with Remote Call
B(); \\Dispatches another event with Remote Call
C();
}
I wan't to call C() after both A() and B() have returned from their call and set particular variables. How can i do that?
If you find yourself doing this often (esp. with more than 2 remote calls), you might want to write your own custom class that handles AsyncTokens from remote calls with a final result() function that is invoked when all remote calls end in success.
If not, since ActionScript is single-threaded, you can just use a local variable to track whether both calls have succeeded.
private var resultFromRemoteCallA:Object;
private var resultFromRemoteCallB:Object;
private function handleRemoteCallA(event:ResultEvent):void {
resultFromRemoteCallA = event.result;
C();
}
private function handleRemoteCallB(event:ResultEvent):void {
resultFromRemoteCallB = event.result;
C();
}
private function C():void {
if (resultFromRemoteCallA && resultFromRemoteCallB) {
// do some thing with the results.
}
}
private function update():void {
resultFromRemoteCallA = resultFromRemoteCallB = null;
A(); B();
}
If you expect null values, you might want to use a boolean variable to track the invocation of the result handler instead.
EDIT: since the author indicated that the dispatch happens in another class, another way to do it would be to pass along a responder and attach it to the AsyncToken like so (in the callee):
private function dispatchRemoteCall(resultHandler:Function, faultHandler: Function): void {
var resultToken: AsyncToken = remoteObject.foo('bar'); // remoteObject may or may not have a result/fault handler
resultToken.addResponder(new mx.rpc.Responder(resultHandler, faultHandler));
}
Then, you can pass along listeners to be invoked when the remote call finishes (at which point you can choose to let the dispatching class store the result or handle it in the caller), like so:
private function update(): void {
classA.dispatchRemoteCall(handleRemoteCallA, handleRemoteCallAFault);
}
If you find yourself doing this a lot, you may also want to look into having a framework do global event routing, like Parsley or Spring Actionscript.
Related
I want to override methods for specific commands on the IDatabase to modify the results.
FT.SEARCH should never return duplicate keys but it can when there is some sort of corruption.
I am using another library that calls FT.SEARCH in IDatabase so this part can only be done by changing IDatabase.
I can autogenerate a wrapper and then use this, but it would need to be maintained and updated every time the IDatabase interface changes. It would be unfortunate to need to update the wrapper class even when I didn't need to override the method that changed in IDatabase. Is there another option that would have similar performance that this wrapper does?
Assume I had a class called DatabaseWrapper all methods were virtual and that was in another package example code would look like:
public sealed class MyDatabaseOverrides: DatabaseWrapper
{
private const string RediSearchSearchCommandName = "FT.SEARCH";
public MyDatabaseOverrides(IDatabase wrapped) : base(wrapped)
{
}
public override Task<RedisResult> ExecuteAsync(string command, params object[] args)
{
var resultTask = base.ExecuteAsync(command, args);
if (string.Equals(RediSearchSearchCommandName, command, StringComparison.OrdinalIgnoreCase))
{
return SkipAndLogDuplicateKeys(resultTask);
}
return resultTask;
}
private async Task<RedisResult> SkipAndLogDuplicateKeys(Task<RedisResult> resultTask)
{
// implementation omitted for brevity
return await resultTask;
}
}
In an AIR application, I have a private variable and a setter:
private var _saveResult
public function set saveResult( result:String ):void
{
_saveResult = result;
dispatchEvent( new resultUpdatedEvent( _saveResult ));
}
The first time that I set "saveResult" the event fires. But it will never fire again unless I restart the application.
If I change the setter to:
public function set saveResult( result:String ):void
{
_saveResult = result;
if ( result != null)
{
dispatchEvent( new resultUpdatedEvent( _saveResult ));
}
}
The problem goes away, I can set the variable many times and the event fires every time.
My question:
Am I doing something wrong here? If not, can anyone explain to me whats happening? If so, what SHOULD I be doing?
Thanks!
It looks like you're constructing your event incorrectly. The first parameter of an Event object should always be a string. So in this case you'd want to always use the same string so you could listen for the event. What does your resultUpdatedEvent class look like? You'll want it to look something like this:
package myEvents
{
import flash.events.Event;
public class PropertyChangeEvent extends Event
{
public static const PROPERTY_CHANGE:String = "propertyChange";
public var result:String = "";
// Public constructor.
public function PropertyChangeEvent (type:String,
result:String="") {
// Call the constructor of the superclass.
super(type);
// Set the new property.
this.result= result;
}
// Override the inherited clone() method.
override public function clone():Event {
return new PropertyChangeEvent(type, result);
}
}
}
That way, when you go to dispatch your event, you can construct the event as follows:
new PropertyChangeEvent(PropertyChangeEvent.PROPERTY_CHANGE, result);
That way, you're listening for the event "PropertyChangeEvent.PROPERTY_CHANGE", which never changes. The problem is now your event listener is probably listening for an event represented by the string saved in result, and obviously, this changes after the first time it's set, so there's no way to assign a listener to it.
For more information about how events work in AS3: http://livedocs.adobe.com/flex/3/html/help.html?content=events_02.html
Per the comments...
There was no event dispatcher problem.
I misdiagnosed the problem, the REAL problem was that if you have a [Bindable] property and you use a setter, and you set it for the current value, flex will ignore it. SO, you have several choices:
1) give the getter and setter different names. Seems like a "bad idea" but it does fix the problem.
2) remove [Bindable] from either the class (my problem) or the property. If the class does not implement IEventDispatcher, you will need to do so. You can simply "extends Sprite" to see it work, but that seems like a "bad idea" as a solution, so I implemented IEventDispatcher per the example at the end of this page: http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/events/IEventDispatcher.html
3) I am sure that there is a way to get around this bug, but I don't actually NEED the class to be [Bindable] so I did not find a work around.
Web service calls are asynchronous in flex, but I wanted to wrap a web service call in a class to provide synchronous encapsulation. Something like the below - the user could call getMyMethodResult and get the result returned by the web service. I expected the thread that recieved the soap response would populate the variable _result and mean that getMyMethod would, after a time, find _result is not longer null. But it doesn't! Can anyone explain why this does not work?
public class myClass
{
private var _result:Object;
public function myClass()
{
//create a web service object
...
// Add listener
_service.addMyMethodListener(myMethodListener);
}
public function getMyMethodResult()
{
_service.myMethod();
while (_result == null)
{
// count a variable or something (unimportant)
}
return _result;
}
private function myMethodListener(event:Event):void
{
_result = event.result;
}
}
There's is absolutely no support for that. The event loop runs between frames and as long as you block the execution with your (infinite) loop, your myMethodListener function will not be called. Anyway, this would be a terrible idea since the absence of threading in the Flash Player will cause your UI to freeze while you wait for your service to return. You should just drop that idea.
I'm testing some event dispatch code in a Flex app, using FlexUnit's addAsync method for testing that events are dispatched. Great so far, I can ensure that at least one event was fired. However, I want to be a bit more detailed; I want to ensure that exactly the set of events I'm expecting are dispatched. Is there a useful test pattern (or, even, different test framework -- I'm flexible!) to accomplish this?
I tried this code, but it doesn't seem to get invoked the second time:
protected function expectResultPropertyChange(event: Event, numberOfEvents: int = 1): void {
trace("Got event " + event + " on " + event.target + " with " + numberOfEvents + " traces left...");
assertTrue(event.type == ResponseChangedEvent.RESPONSE_CHANGED);
if (numberOfEvents > 1) {
event.target.addEventListener(ResponseChangedEvent.RESPONSE_CHANGED, addAsync(expectResultPropertyChange, 1000, numberOfEvents - 1));
}
}
public function testSomething(): void {
requiredQuestion.addEventListener(ResponseChangedEvent.RESPONSE_CHANGED, addAsync(expectResultPropertyChange, 1000, 2));
requiredQuestion.responseSelected("1", true);
requiredQuestion.responseSelected("2", true);
}
In response to the comment...
What if the event is dispatched
directly? responseSelected doesn't
trigger an asynchronous event on a
composite object, it simply dispatched
the RESPONSE_CHANGED event itself
directly. I'm not seeing how this
approach can be mocked using your
method. Mind you, I'm fuzzy on the
mock testing practice as-is, so I'm
probably missing a simple solution
here.
..in that case you don't need to use a mock or addAsync. Something like this will do:
public function testSomething(): void
{
var requiredQuestion : RequiredQuestion = new RequiredQuestion();
var callCount : int = 0;
requiredQuestion.addEventListener(ResponseChangedEvent.RESPONSE_CHANGED, function(event : ResponseChangedEvent)
{
callCount++;
});
requiredQuestion.responseSelected("1", true);
requiredQuestion.responseSelected("2", true);
assertEquals(2, callCount);
}
This is going to be a high level example of how a similar problem could be solved using a mocked out object of whatever it is that's doing the asynchronous call. Obviously i can't see your code so i can't give you a precise example.
So, as i said in the comment, you can mock out a dependency in a class to fake asynchronous calls so that they become synchronous. Take the below class
public class RequiredQuestion extends EventDispatcher
{
private var someAsynchronousObject : IAsynchronousObject;
public function RequiredQuestion(someAsynchronousObject : IAsynchronousObject = null)
{
someAsynchronousObject = someAsynchronousObject || new AsynchronousObject();
someAsynchronousObject.addEventListener(Event.COMPLETE, asyncCallComplete);
}
public function responseSelected(id : String, flag : Boolean) : void
{
//Will asynchronously fire the Event.COMPLETE event
someAsynchronousObject.startAsynchrounsCall();
}
protected function asyncCallComplete(event : Event) : void
{
dispatchEvent(new ResponseChangedEvent(ResponseChangedEvent.RESPONSE_CHANGED));
}
}
So by default you are using the concrete class that you want to use unless someAsynchronousObjec is injected into the class via the constructor. AsycnhronousObject probably has it's own unit tests or it's in an external class so you don't really want, or need to be testing its functionality. What you can now do is create a mock object that implements IAsynchronousObject that can be used to fake its behavior. Using the ASMock framework the test could look something like this:
public function testSomething(): void
{
var mockIAsycnhronousObject : IAsynchronousObject =
IAsynchronousObject(mockRepository.createStrict( IAsynchronousObject));
SetupResult.forEventDispatcher(mockIAsycnhronousObject);
SetupResult.forCall(mockIAsycnhronousObject.startAsynchronousCall())
.dispatchEvent(new Event(Event.COMPLETE)); // all calls to the startAsynchronousCall method and dispatch the complete event everytime it's called.
mockRepository.replayAll();
var requiredQuestion : RequiredQuestion = new RequiredQuestion(mockIAsycnhronousObject);
var callCount : int = 0;
requiredQuestion.addEventListener(ResponseChangedEvent.RESPONSE_CHANGED, function(event : ResponseChangedEvent)
{
callCount++;
});
requiredQuestion.responseSelected("1", true);
requiredQuestion.responseSelected("2", true);
assertEquals(2, callCount);
mockRepository.verifyAll();
}
This is just one example of how mocking can help you unit tests. There's a whole wealth of info out there on mocking although it is still very new to ActionScript (released in December). ASMock is based on the .net Rhino mocks so searching for Rhino mocks should throw up a lot more results if you need help.
Definitely a different way of thinking but once you get into it you tend to wonder how you got by in unit testing without them.
I bumped into an additional question that I needed in regards to this: Using an IEnumerable<T> as a delegate return type
From the above solution, the following was suggested:
class Example
{
//the delegate declaration
public delegate IEnumerable<T> GetGridDataSource<T>();
//the generic method used to call the method
public void someMethod<T>(GetGridDataSource<T> method)
{
method();
}
//a method to pass to "someMethod<T>"
private IEnumerable<string> methodBeingCalled()
{
return Enumerable.Empty<string>();
}
//our main program look
static void Main(string[] args)
{
//create a new instance of our example
var myObject = new Example();
//invoke the method passing the method
myObject.someMethod<string>(myObject.methodBeingCalled);
}
}
Notice that in someMethod, the delegate "method()" is called. Is there anyway to set a class-level delegate that is called later on?
I.e:
class Example {
//the delegate declaration
public delegate IEnumerable<T> GetGridDataSource<T>();
//this fails because T is never provided
private GetGridDataSource<T> getDS;
//the generic method used to call the method
public void someMethod<T>(GetGridDataSource<T> method)
{
getDS = method;
}
public void anotherMethod() {
getDS();
}
}
Depending on what you are trying to achieve and where you have flexibility in your design, there are a number of options. I've tried to cover the ones that I feel most probably relate to what you want to do.
Multiple values of T in a single instance of a non-generic class
This is basically what you seem to want. However, because of the generic nature of the method call, you'll need a class level variable that can support any possible value of T, and you will need to know T when you store a value for the delegate.
Therefore, you can either use a Dictionary<Type, object> or you could use a nested type that encapsulates the class-level variable and the method, and then use a List<WrapperType<T>> instead.
You would then need to look up the appropriate delegate based on the required type.
class Example {
//the delegate declaration
public delegate IEnumerable<T> GetGridDataSource<T>();
//this works because T is provided
private Dictionary<Type, object> getDSMap;
//the generic method used to call the method
public void someMethod<T>(GetGridDataSource<T> method)
{
getDSMap[typeof(T)] = method;
}
//note, this call needs to know the type of T
public void anotherMethod<T>() {
object getDSObj = null;
if (this.getDSMap.TryGetValue(typeof(T), out getDSObj))
{
GetGridDataSource<T> getDS = getDSObj as GetGridDataSource<T>;
if (getDS != null)
getDS();
}
}
Single value of T in a single instance of a non-generic class
In this case, you could store the delegate instance in a non-typed delegate and then cast it to the appropriate type when you need it and you know the value of T. Of course, you'd need to know T when you first create the delegate, which negates the need for a generic method or delegate in the first place.
Multiple values of T in multiple instances of a generic class
Here you can make your parent class generic and supply T up front. This then makes the example you have work correctly as the type of T is known from the start.
class Example<T> {
//the delegate declaration
public delegate IEnumerable<T> GetGridDataSource<T>();
//this works because T is provided
private GetGridDataSource<T> getDS;
//the generic method used to call the method
public void someMethod<T>(GetGridDataSource<T> method)
{
getDS = method;
}
public void anotherMethod() {
if (getDS != null)
getDS();
}
}
You either need to make the type generic as well, or use plain Delegate and cast back to the right type when you need to invoke it. You can't just use T outside a generic context - the compiler will think you're trying to refer to a normal type called T.
To put it another way - if you're going to try to use the same type T in two different places, you're going to need to know what T is somewhere in the type... and if the type isn't generic, where is that information going to live?