HI, I try to understant how to send a message directly to a speciciel Target. I got a small SL projet and and a dunmmy class named class1. I register in the class constructor and listenig for all string type message.
public class Class1
{
public Class1()
{
Messenger.Defaut.Register<String>(this, f => { TraiteMessage(f); });
}
public void TraiteMessage(string sMessage)
{
MessageBox.Show("Class1:" + sMessage);
}
}
Now I send the message like this:
Messenger.Defaut.Send<String, Class1>("test message");
The message do not reach the target. When I look into the internal source code of the MVVM light i can see that the test are done like: item.Action.Target.GetType() == messageTargetType but in fact the messageTargetType are set to: MyProejet.Class1 but the item.Action.Target.GetType() return something like: {System.Collections.Generic.Dictionary2System.Type,System.Collections.Generic.List1[SLDuninLib.Messages.Avise+WeakActionAndToken]]} System.Type {System.RuntimeType}
what do i do wrong?
Thanks for your help
Is an instance of Class1 created anywhere? If not, then it never registers to receive any messages.
You can easily test this by putting a breakpoint on the line of code that registers to receive the message in the Class1 constructor.
I tested your code and it works when I have the message registration in another view model, but this is because any view models in the ViewModelLocator are created as soon as the App.xaml is loaded.
When TTarget defined, the message is awared by its type, not instance.
So, your code did not work (as you experienced) because you sent a message with Class1 type but receipient you register was String type, not Class1 type.
So, in this case, several solutions can be considered.
Make Class1 static and handle received message as below:
Messenger.Defaut.Register<Class1>(this, msg => { Class1.TraiteMessage(msg); });
Or, send message in string type same as registered type.
Messenger.Defaut.Send<String, String>("test message");
Or, define a small struct which contains variables you want to transfer between them as below.
public struct SearchTerm
{
public string Category;
public string Keyword;
}
send as below:
Messenger.Default.Send(new SearchTerm{Category = "Q",Keyword = "something"}));
and consume in Class1 as below:
Messenger.Default.Register<SearchTerm>(this,msg => {TraiteMessage(msg.Keyword);});
For me, the last solution is prefered.
Cheers
Related
Maybe I'm missing something really simple out here but gonna ask anyways.....
I am using Xamarin forms (.NET Standard project), MVVMLight, Realm DB and ZXing Barcode Scanner.
I have a realmobject like so...
public class Participant : RealmObject
{
public string FirstName {get; set;}
public string LastName {get; set;}
public string Email {get; set;}
public string RegistrationCode {get; set;}
//More properties skipped out for brevity
}
I have the corresponding viewmodel as follows:
public class ParticipantViewModel
{
Realm RealmInstance
public ParticipantViewModel()
{
RealmInstance = Realms.Realm.GetInstance();
RefreshParticipants();
}
private async Task RefreshParticipants()
{
//I have code here that GETS the list of Participants from an API and saves to the device.
//I am using the above-defined RealmInstance to save to IQueryable<Participant> Participants
}
}
All the above works fine and I have no issues with this. In the same viewmodel, I am also able to fire up the ZXing Scanner and scan a bar code representing a RegistrationCode.
This, in turn, populates the below property (also in the viewmodel) once scanned...
private ZXing.Result result;
public ZXing.Result Result
{
get { return result; }
set { Set(() => Result, ref result, value); }
}
and calls the below method (wired up via the ScanResultCommand) to fetch the participant bearing the scanned RegistrationCode.
private async Task ScanResults()
{
if (Result != null && !String.IsNullOrWhiteSpace(Result.Text))
{
string regCode = Result.Text;
await CloseScanner();
SelectedParticipant = Participants.FirstOrDefault(p => p.RegistrationCode.Equals(regCode, StringComparison.OrdinalIgnoreCase));
if (SelectedParticipant != null)
{
//Show details for the scanned Participant with regCode
}
else
{
//Display not found message
}
}
}
I keep getting the below error....
System.Exception: Realm accessed from incorrect thread.
generated by the line below....
SelectedParticipant = Participants.FirstOrDefault(p => p.RegistrationCode.Equals(regCode, StringComparison.OrdinalIgnoreCase));
I'm not sure how this is an incorrect thread but any ideas on how I can get around to fetching the scanned participant either from the already populated IQueryable or from the Realm representation directly would be greatly appreciated.
Thanks
Yes, you're getting a realm instance in the constructor, and then using it from an async task (or thread). You can only access a realm from the thread in which you obtained the reference. Since you're only using a default instance, you should be able to simply obtain a local reference within the function (or thread) where you use it. Try using
Realm LocalInstance = Realms.Realm.GetInstance();
at the top of the function and use that. You'll need to recreate the Participants query to use the same instance as its source too. This will be the case wherever you use async tasks (threads), so either change all to get hold of the default instance on entry or reduce the number of threads that access the realm.
Incidentally I'm surprised you don't get a similar access error from within
RefreshParticipants() - maybe you're not actually accessing data via RealmInstance from there.
I was trying to verify whether my log warning message is written via NUnit mocking. I am getting this error message :
An exception of type 'System.NotSupportedException' occurred in Moq.dll but was not handled in user code
Additional information: Invalid verify on a non-virtual (overridable in VB) member: m => m.LogWarning(String.Format("comments not found for part number :{0}", (Object)0), new[] { "111" })
code:
mockLogger.Verify(m => m.LogWarning($"comments not found for part number :{0}", "111"), Times.Exactly(1));
This is happening because NUnit mocking framework does not support extension methods. A few people on stack overflow have suggested to use Log method instead of level wise methods.
What am I missing?
Firstly, you don't need the $ at the start of the string. That's for string interpolation. The LogWarning message is doing a string.format, hence the {0}
Mock frameworks cannot directly mock static methods. The problem in your case is the LogWarning method - that is the static (extension) method.
The simplest way of overcoming this issue is by using a wrapper class. Here's how I got it, in your case.
Firstly I created an interface
public interface IMyLogWarning
{
void LogWarning(string msg, params object[] args);
}
Then I created a class which implements that interface
public class MyLogWarning<T> : IMyLogWarning where T : class
{
private readonly ILogger _logger;
public MyLogWarning(ILogger<T> logger)
{
// Using constructor for DI
_logger = logger;
}
public void LogWarning(string msg, params object[] args)
{
_logger.LogWarning(msg, args);
}
}
The reason for these two is that I'll use these in my code as well as the unit test.
The constructor in the class is setup so it can be populated using dependency injection, something like this in your ConfigureServices method. Feel free to change this; was a quick stab at it on my part.
services.AddTransient<IMyLogWarning, MyLogWarning<MyViewModel>>();
You can then create a unit test that's roughly like this
[Test]
public void LoggingTest_LogAMessage_ConfirmedLogWasRun()
{
// TODO - add the rest of your test code
// Arrange
var warningMsg = "comments not found for part number :{0}";
var partNumber = "111";
var mockLogger = new Mock<IMyLogWarning>();
// Act
mockLogger.Object.LogWarning(warningMsg, partNumber);
// Assert
mockLogger.Verify(m => m.LogWarning(warningMsg, partNumber), Times.Exactly(1));
}
I have a custom domain class with a single constructor that takes a String, as well as a toString() method. The constructor decodes the input string, performs validations on it and throws IllegalArgumentException if invalid.
I want to bind directly to this field, as described here: http://blog.springsource.org/2009/11/17/spring-3-type-conversion-and-validation/ (see 'Convention Over Configuration' section).
That is working fine & I am displaying the error message resolved by Spring (typeMismatch on barcodeInfo).
I know that I can customize this error message using a messageSource entry, e.g.
typeMismatch.barcodeInfo=Invalid format
However, the error message that I want to display isn't always the same, it depends on the value of the input string. Hence, I want to display the error message that I originally used in the IllegalArgumentException that I threw from the constructor. Is this possible?
I am specifically looking for a solution which will work with Spring WebFlow.
You might want to check BindingErrorProcessor used by WebDataBinder. There you can implement your own custom logic for translating exceptions to validation errors.
Notes:
You should implement your own exception (to be able to distinguish it from IllegalArgumentException thorwn by other components).
You can initialize WebDataBinder with your custom BindingErrorProcessor within your #InitBinder method (or set specific WebBindingInitializer to your handler adapter).
As Pavel mentioned in his answer, you can achieve this by implementing BindingErrorProcessor.
It should look like this:
...
import org.springframework.validation.DefaultBindingErrorProcessor;
...
#Controller
public class YourController {
...
#InitBinder
public void initBinder(WebDataBinder binder) {
binder.setBindingErrorProcessor(new DefaultBindingErrorProcessor() {
#Override
public void processPropertyAccessException(
PropertyAccessException ex, BindingResult bindingResult) {
if (ex.getPropertyName().equals("fieldInQuestion")) {
Throwable cause = ex.getMostSpecificCause();
FieldError fieldError;
fieldError = new FieldError(
bindingResult.getObjectName(),
"fieldInQuestion",
cause.getMessage());
bindingResult.addError(fieldError);
} else {
super.processPropertyAccessException(ex, bindingResult);
}
}
});
}
}
I am trying to have a baseclass and register default interception using unity. I am also registering each derived type before resolving, but its not working. I would expect the BaseMethod to be intercepted here but it is not.
public class AbstractResponse
{
private string name;
public virtual void BaseMethod()
{
Console.WriteLine("Base");
}
}
public class DocumentResponse:AbstractResponse
{
public virtual void Test()
{
Console.WriteLine("In Test Method");
}
}
var container = new UnityContainer(); container.AddNewExtension<Interception>();
container.RegisterType<AbstractResponse>(
new DefaultInterceptor<VirtualMethodInterceptor>(),
new DefaultInterceptionBehavior<TraceBehavior>()).
RegisterType<AbstractResponse,DocumentResponse>();
container.Resolve<DocumentResponse>().BaseMethod();
You've just gone a little wrong on your registration code - you are actually calling RegisterType twice in your code sample, and the second registration is overwriting the first one. Switch it to something like this and it will work fine: -
container.RegisterType<AbstractResponse, DocumentResponse>(
new DefaultInterceptor<VirtualMethodInterceptor>(),
new DefaultInterceptionBehavior<TraceBehaviour>());
So this says "Register AbstractResponse and map it to DocumentResponse. Then, using the VirtualMethodInterceptor, apply the TraceBehaviour."
You can always see if the interception is active by seeing the type that is returned on Resolve - if it's the (in this case) AbstractResponse then it hasn't worked; if you get back some funky Unity-generated type name then it's working.
I'm pretty new to MVVM light world, and after searches I can't find what I want to do.
My WP7 application contains a pivot, each pivot item content is View1 and viewmodel is VM1.
When loading my application, I'd like to create every pivot item with the same view and view model but with different parameter.
example :
PivotItem 1 -> send param "car" to the view model
PivotItem 2 -> send param "truck" to the view model, etc.
Google told me to use messaging but if I send 2 messages from my MainViewModel, both PivotItem1 and PivotItem2 ViewModel will receive these messages.
Am I wrong with this approach ?
Is there another solution to succeed ?
Thank you in advance for your answer.
PS : be indulgent, english is not my native language, don't hesitate to ask for further information.
Regards,
Aymeric Lagier
To seperate the messages use the second constructor signature whereby you can pass a token. This token can be anything but I generally use an enum to store all my message types within the system.
Create a static class in a common library and reference this in all projects where you need to send or receive messages.
The following code hopefully shows this approach, notice I am sending a string as a value within the message but this can be anything, even a complex object such as one of your business objects.
namespace MyProject.Common
{
public static class AppMessages
{
enum MessageTypes
{
ViewmodelA,
ViewmodelB
}
public static class ViewModelAUpdate
{
public static void Send(string value)
{
Messenger.Default.Send(value, MessageTypes.ViewmodelA);
}
public static void Register(object recipient, Action<string> action)
{
Messenger.Default.Register(recipient, MessageTypes.ViewmodelA, action);
}
}
public static class ViewModelBUpdate
{
public static void Send(string value)
{
Messenger.Default.Send(value, MessageTypes.ViewmodelB);
}
public static void Register(object recipient, Action<string> action)
{
Messenger.Default.Register(recipient, MessageTypes.ViewmodelB, action);
}
}
}
}
How about using a method to set the message you want to receive. (this could be done as a parameter in the constructor or a property as well)
public void RegisterForAppMessage(AppMessages.MessageTypes messageType)
{
switch (messageType)
{
case AppMessages.MessageTypes.PivotViewItem1Message:
AppMessages.PivotViewItem1Message.Register(this,DoSomethingWhenIRecievePivotViewItem1Messages)
break;
case AppMessages.MessageTypes.PivotViewItem2Message:
AppMessages.PivotViewItem2Message.Register(this,DoSomethingWhenIRecievePivotViewItem2Messages)
break;
}
}
private void DoSomethingWhenIRecievePivotViewItem2Messages(string obj)
{
// TODO: Implement this method
throw new NotImplementedException();
}
private void DoSomethingWhenIRecievePivotViewItem1Messages(string obj)
{
// TODO: Implement this method
throw new NotImplementedException();
}
Messaging sounds a bit heavy for this purpose. Could you simply inject a parameter into your ViewModel. If you already have MVVMLight you also have support for SimpleIOC. Maybe let the view locate its ViewModel when the view is resolved and there decide which parameter to use on the view model?
You can see an example of it here