I'm hoping this isn't too dumb a question: I just started using MVVM light (love it so far! ). In the "before time" (ie before the use of MVVML), I had to ui dispatch any code that would hit a property setter that had an INotifyPropertyChanged event raised in it.
I had (incorrectly? ) thought that requirement would disappear when using MVVMlight.
I still have to use it, correct? My experiments tell me a resounding yes.
So, heres the really stupid part - since there is a requirement to initialize the MVVML dispatcherhelper class somewhere, where I assume it saves the UI thread, why not have the RaisePropertyChanged call do the Dispatch automagically? It seems like a common thing to do?
Not a criticism per se, more of a "how come it doesn't work this way" :-)
Edit (copied from from a comment by author)
FWIW, I did this:
public class QViewModelBase : ViewModelBase {
protected override void RaisePropertyChanged(string propertyName) {
DispatcherHelper.CheckBeginInvokeOnUI( () => base.RaisePropertyChanged(propertyName));
}
protected override void RaisePropertyChanged<T>(string propertyName, T oldValue, T newValue, bool broadcast) {
DispatcherHelper.CheckBeginInvokeOnUI( () => base.RaisePropertyChanged<T>(propertyName, oldValue, newValue, broadcast));
}
}
Please refer to my answer here: Thread safe, Silverlight
I highly recommend exactly what you are suggesting.
IMO you don't need to dispatch at all!
Only operations on ObservableCollection need dispatching.
Reference answer: Accessing ViewModel properties from separate thread
Related
Good day!
Wondering if using fireUserEventTriggered/userEventTriggered is netty way to collaborate with callback-oriented external services while processing message in channel handlers?
I mean, if there is some "alien" service with nonblocking(callback mechanic) methods, is this is right way to call ChannelHandlerContext#fireUserEventTriggered(passing some params from callback closure) and then handle it within overloaded ChannelInboundHandler#userEventTriggered for continue communication within original channel where it all started.
Example for illustration
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
externalServiceWithAsyncApi.doAndRegisterCallback(
//some call that will finish later and trigger callback handler
(callbackParam)->
ctx.fireUserEventTriggered(
new ExternalServiceCallbackEvent(callbackParam)
)
);
}
#Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
//seems its for us to handle
if (evt instanceof ExternalServiceCallbackEvent) {
//some processing and answer in the original?
ctx.channel()
.writeAndFlush(...)
.addListener(...);
// let other handlers process
} else {
super.userEventTriggered(ctx, evt);
}
}
Seems example with HeartbeatHandler in "Netty in Action" (in Listing 11.7) is relevant, but this part is a bit ahead from my current point of reading, so decided to ask for a help.
There is very similar question but something did not work for author and no answer Netty, writing to channel from non-Netty thread
UPD
The correct way seems to call NOT
ctx.fireUserEventTriggered(...)
but
ctx.channel().pipeline().fireUserEventTriggered(...)
It's definitely something you could used for that. That said you can also just do the write directly from your callback.
We are evaluating Grid Gain 6.5.5 at the moment as a potential solution for distribution of compute jobs over a grid.
The problem we are facing at the moment is a lack of a suitable asynchronous notification mechanism that will notify the sender asynchronously upon job completion (or future completion).
The prototype architecture is relatively simple and the core issue is presented in the pseudo code below (the full code cannot be published due to an NDA). *** Important - the code represents only the "problem", the possible solution in question is described in the text at the bottom together with the question.
//will be used as an entry point to the grid for each client that will submit jobs to the grid
public class GridClient{
//client node for submission that will be reused
private static Grid gNode = GridGain.start("config xml file goes here");
//provides the functionality of submitting multiple jobs to the grid for calculation
public int sendJobs2Grid(GridJob[] jobs){
Collection<GridCallable<GridJobOutput>> calls = new ArrayList<>();
for (final GridJob job : jobs) {
calls.add(new GridCallable<GridJobOutput>() {
#Override public GridJobOutput call() throws Exception {
GridJobOutput result = job.process();
return result;
}
});
}
GridFuture<Collection<GridJobOutput>> fut = this.gNode.compute().call(calls);
fut.listenAsync(new GridInClosure<GridFuture<Collection<GridJobOutput>>>(){
#Override public void apply(GridFuture<Collection<GridJobOutput>> jobsOutputCollection) {
Collection<GridJobOutput> jobsOutput;
try {
jobsOutput = jobsOutputCollection.get();
for(GridJobOutput currResult: jobsOutput){
//do something with the current job output BUT CANNOT call jobFinished(GridJobOutput out) method
//of sendJobs2Grid class here
}
} catch (GridException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
return calls.size();
}
//This function should be invoked asynchronously when the GridFuture is
//will invoke some processing/aggregation of the result for each submitted job
public void jobFinished(GridJobOutput out) {}
}
}
//represents a job type that is to be submitted to the grid
public class GridJob{
public GridJobOutput process(){}
}
Description:
The idea is that a GridClient instance will be used to in order to submit a list/array of jobs to the grid, notify the sender how many jobs were submitted and when the jobs are finished (asynchronously) is will perform some processing of the results. For the results processing part the "GridClient.jobFinished(GridJobOutput out)" method should be invoked.
Now getting to question at hand, we are aware of the GridInClosure interface that can be used with "GridFuture.listenAsync(GridInClosure> lsnr)"
in order to register a future listener.
The problem (if my understanding is correct) is that it is a good and pretty straightforward solution in case the result of the future is to be "processed" by code that is within the scope of the given GridInClosure. In our case we need to use the "GridClient.jobFinished(GridJobOutput out)" which is out of the scope.
Due to the fact that GridInClosure has a single argument R and it has to be of the same type as of GridFuture result it seems impossible to use this approach in a straightforward manner.
If I got it right till now then in order to use "GridFuture.listenAsync(..)" aproach the following has to be done:
GridClient will have to implement an interface granting access to the "jobFinished(..)" method let's name it GridJobFinishedListener.
GridJob will have to be "wrapped" in new class in order to have an additional property of GridJobFinishedListener type.
GridJobOutput will have to be "wrapped" in new class in order to have an addtional property of GridJobFinishedListener type.
When the GridJob will be done in addition to the "standard" result GridJobOutput will contain the corresponding GridJobFinishedListener reference.
Given the above modifications now GridInClosure can be used now and in the apply(GridJobOutput) method it will be possible to call the GridClient.jobFinished(GridJobOutput out) method through the GridJobFinishedListener interface.
So if till now I got it all right it seems a bit clumsy work around so I hope I have missed something and there is a much better way to handle this relatively simple case of asynchronous call back.
Looking forward to any helpful feedback, thanks a lot in advance.
Your code looks correct and I don't see any problems in calling jobFinished method from the future listener closure. You declared it as an anonymous class which always has a reference to the external class (GridClient in your case), therefore you have access to all variables and methods of GridClient instance.
I am working on a Silverlight application using V3 SP1 of MVVM Light Toolkit.
My application is fully French/English. All UI elements (buttons, labels, etc.) and all the data (models). I need dynamic language switching and this is fully implemented and works with anything coming from a resource file. What I am struggling with is the ViewModels.
The Models have language specific prperties (DescriptionEn, DescriptionFr) and an additional property call LocalizedDescription which uses the current culture to return call the language specific property.
When the language changes (via a button click) I raise and broadcast (via the Messenger) a property changed event.
In each of my ViewModels, I register to receive the property changed message for the language swap.
I want to notify all the properties of the ViewModel that something has changed.
From: http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.propertychanged.aspx
The PropertyChanged event can indicate all properties on the object have changed by using either null or String.Empty as the property name in the PropertyChangedEventArgs.
However, since the toolkit abstracts the raising of the changed event with RaisePropertyChanged(...) I cannot get this to work. I have also examined the source of the tookit and discovered that RaisePropertyChanged calls VerifyPropertyName(..) which in turn returns an error is the property does not belong to the ViewModel. I also noticed that the VerifyPropertyName method is attributed with Conditional("DEBUG"), but even if I choose the Release configuration, the ArgumentException("Property not found") is still raised.
Does anyone know of a way to get this to work using the toolkit aside from manually calling RaisePropertyChanged for every property of the ViewModel?
Follow-up:
Based on the comment from Simon, I attempted to create my own class that extends ViewModelBase. I looked at the source on CodePlex and decided to create a single method called RaiseAllPropertyChanged(). It would simply be a copy of the RaisePropertyChanged(string propertyName) but without the parameter and without the call to VerifyPropertyName(...). I cannot get it to work. Here is what I have.
public class ViewModelBaseExtended : ViewModelBase
{
protected void RaiseAllPropertyChanged()
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(String.Empty));
}
}
}
But I get a compiler error: The event 'GalaSoft.MvvmLight.ViewModelBase.PropertyChanged' can only appear on the left hand side of += or -=. This is a copy of the code that is used in the ViewModelBase.
Can someone offer some advice as to how to get this to work?
Solution:
I copied all the code from ViewModelBase into a new class. I then added the method RaisePropertyChanged() mentioned above which instantiates the PropertyChangedEventArgs class with String.Empty. This is now the new subclass for my ViewModels.
Thanks again to Simon for leading the way!
In case you're reading this in 2016, you can use ObservableObject and notify that all of the properties have changed by doing:
RaisePropertyChanged(string.Empty);
Unfortunately this is not possible with the current code-base of MVVMLight
In the short term your have 2 options:
User your own custom base class. And by custom base class I mean "Do not inherit from the MVVMLight class".
Download and compile MVVMLight in Release mode. This will force the "VerifyPropertyName" method to be excluded. Of course then you don't get the value of property name checks.
I am sure Laurent Bugnion will have this fixed soon.
A lighter solution to this problem would have been to override RaisePropertyChanged(string propertyName) in your class :
protected override void RaisePropertyChanged(string propertyName)
{
if (propertyName != null)
{
base.RaisePropertyChanged(propertyName);
}
else
{
var handler = PropertyChangedHandler;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(null));
}
}
}
I am trying to dispatch a custom event from one flex module to another.
The code which dispatch the event is as below
Application.application.Destination.child.dispatchEvent(
new AlgoEvent(AlgoEvent.GETFROMPARENT_LOCAL_EVENT));
here AlgoEvent is a custom event
on the other side the module which catches and handles the event has this code:
public function sendParametersToChild(e:AlgoEvent):void
{
//some codes
}
but when the statement Application.application.Destination.child.dispatchEvent(new AlgoEvent(AlgoEvent.GETFROMPARENT_LOCAL_EVENT)); is executed the debugger give the following run time exception:
TypeError: Error #1034: Type Coercion failed: cannot convert resources.events::AlgoEvent#4182239 to resources.events.AlgoEvent.
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\core\UIComponent.as:9298]
at components::Destination/sendTimeToChild()[E:\FlexProjects\MyApp\src\components\Destination.mxml:99]
at components::Destination/updateParameters()[E:\FlexProjects\MyApp\src\components\Destination.mxml:206]
at components::Destination/__CreateBasketButton_click()[E:\FlexProjects\MyApp\src\components\Destination.mxml:558]
I am not able to identify what is going wrong here.
Please help to solve this problem
This is my Event class
public class AlgoEvent extends Event
{
public static const GETFROMPARENT_LOCAL_EVENT:String = "getfromparent_local";
private var eventType:String;
public function AlgoEvent(eventType:String, bubbles:Boolean=false, cancelable:Boolean=false)
{
super(eventType,bubbles,cancelable);
this.eventType=eventType;
}
}
While debugging am getting error in this funcion of UIComponent class
override public function dispatchEvent(event:Event):Boolean
{
if (dispatchEventHook != null)
dispatchEventHook(event, this);
return super.dispatchEvent(event);
}
Excaxtly this line gives the error: dispatchEventHook(event, this);
Import the AlgoEvent class in the main application and create a reference to it.
import resources.events.AlgoEvent;
private var dummyEvent: AlgoEvent;
Some explanations for this could be found here: Module domains
If your custom event doesn't carry any special event properties you could workaround your problem by using the standard Event class.
dispatchEvent(new Event(AlgoEvent.GETFROMPARENT_LOCAL_EVENT));
I had the same problem when dispatching, solved overriding two functions:
override public function clone():Event
{
return new AlgoEvent(type, bubbles, cancelable);
}
override public function toString():String
{
return formatToString("AlgoEvent","type"","bubbles","cancelable","eventPhase");
}
hope it helps out :)
Mr. splash suggested a solution which worked fro me:
Try to make the Custum Event (Algo Event in my case) class known to the main application.
I.e import it in the main application and create a variable of it..
And it works for a main reason>>when we try to communicate betwwen the modules using event dispatching what happens is :the modules are loaded at the run time but the classes like event classes are linked to the modules at the run time..
But the Event class is compiled before the modules are loaded..
application defines a Custum Event Class at compile time, and the module defines its own Custum Event Class when it is published. Then when the application is run, the Custum Event Class dispatched in the application doesn't match the one in the module
swf.
For the problem which is causing this error one can check the link:
http://www.kirupa.com/forum/showthread.php?t=320390
and also
http://www.jeffdepascale.com/index.php/flash/custom-events-in-loaded-swf-files/
Mate framework takes care of all this.
It gives you a global event bus, for all modules in your app.
http://mate.asfusion.com/
Try to override the clone() method in your customized Event,AlgoEvent.
Add the following code to your AlgoEvent.as class and try:
override public function clone():Event{
return new AlgoEvent(eventType,bubbles,cancelable);
}
HTH.
Your custom Event class should look like this:
public class AlgoEvent extends Event
{
public static const GETFROMPARENT_LOCAL_EVENT:String = "getfromparent_local";
public function AlgoEvent(type:String, bubbles:Boolean=false, cancelable:Boolean=false)
{
super(type, bubbles, cancelable);
};
override public function clone():AlgoEvent
{
return new AlgoEvent(type, bubbles, cancelable);
};
};
You should use the Event's inherited type property instead of creating a new one.
Also, the UIComponent has it's own dispatchEvent method, so you don't have to create your own - only if it works differently to the inherited one.
Regards,
Rob
Okay, it must be said that what you're doing, from an architectural standpoint, is wrong. Calling Application.application is bad for so many reason, especially if you're then starting to go down the display tree. The second any of the children changes, your build is now broke, and you won't know that until runtime because it's a module.
What you need is an application framework. A way to increase complexity without decreasing maintainability. There are many out there, but my personal favorite is Parsley. I've used it on many very large projects with much success. The problem you're trying to solve right now, dispatching one event where the other module listens for it, is extremely trivial (can be done in about 3 lines of code).
I recommend you look it over as well as my presentation on an introduction to parsley.
Since there is no ErrorProvider class in .NETCF, how can I implement similar functionality (not necessarily exactly like ErrorProvider)?
I am using all the regular databinding constructs to bind controls to a datatable, using the DataRow.RowError property and DataRow.SetColumnError method, but I can't find events on any of DataTable, BindingManagerBase, etc. that I can hook into to receive any sort of notification.
Am I stuck calling a method to manually iterate through all the controls on my form and change some look/feel of the bound control?
Thanks,
MrB
The ErrorProvider class seems pretty basic - actually, a little too basic. If you have Red Gate Reflector, I would recommend disassembling the class and looking at it. Otherwise, create a Dictionary<Control, String>.
Here is a quick idea on creating your own provider:
Dictionary<Control, String> ErrorSet = new Dictionary<Control, String>();
public void SetError(Control control, String message)
{
// code for adding error information
ErrorSet.Add(control, message);
}
public String GetError(Control control)
{
// code for retrieving error information
return ErrorSet[control];
}
public String Clear()
{
// code for clearing all errors
}
I don't have R-G reflector here or I would provide more sample methods. But this ought to provide some sort of sample to work from.