Clicky crisp viewmodel code#
Now, let’s look a simple code example that uses the above event. Public class ItemSelectedEvent : CompositePresentationEvent If you for example were to define a class for an event that passes an instance of the Item class shown below between a publisher and subscriber, it could be implemented something like this: Prism comes with a .CompositePresentationEvent class that inherits from this one, where the TPayload type parameter specifies the type of argument that will be passed to the subscribers. An event object is a class that inherits from the abstract .EventBase class.
To be able to pass an event from a publisher to a subscriber using Prism’s event aggregator, the first thing you need to do is to define the actual type of the event to be passed. TEventType GetEvent() where TEventType : EventBase, new() An instance of an event object of type TEventType. Prism – the official guidance for building composite XAML based applications from the Microsoft Patterns and Practices Team – for example ships with a .EventAggregator class that implements the following interface: Publishers call publication methods of the event aggregator class to notify subscribers while subscribers call subscription methods to receive notifications.Īlthough you can implement your own event aggregator class, there is often little reason do to so as most MVVM frameworks out there has an event aggregator or message bus built in. The responsibility of this class is simply to aggregate events. In order to implement this pattern, which is also sometimes referred to as the message bus pattern, both the publishers and the subscribers need a reference to a class that represents the event aggregator. The subscriber observes the event aggregator instead of the publisher and the publisher knows only about the event aggregator and not about the subscribers. It could potentially also lead to memory leaks if a publisher of an event lives longer than a subscriber and you forget to, or don’t know when to, unsubscribe from an event.īy introducing an event aggregator in between the publishers and subscribers, you can remove this tight coupling. However, using this approach will result in a tight coupling between publishers and subscribers that makes the application harder to maintain. NET events or by keeping a direct reference to each subscriber from each publisher class and simply call a method on the subscriber class from the publisher class once you want to publish some information. If you are developing a composite user interface that contains several parts that need to be synchronized with each other, you need to be able to communicate between these different parts of your application.
Clicky crisp viewmodel windows#
Make the property names of your data match the property names of your viewmodel.Using the event aggregator pattern to communicate between view models Posted: Febru| Author: Magnus Montin | Filed under: MVVM | Tags: MVVM, Prism, Silverlight, Windows Store Apps, WPF, XAML | 13 Comments Write your viewmodels in such a way that they initialize themselves from a parameter object (i.e. Here is a better approach to viewmodel building. Some kind of loop is necessary to turn the plain objects in the data array into FoodVM instances. That means the one FoodVM is lost - and the items in data do not become FoodVMs on their own. but a few moments later you overwrite that with a simple JS object, data. The next mistake is that you initialize your FoodsList property with a single FoodVM. var self = this īecause of this you were attaching all the observables and the clickCounterAdd function to whatever self happened to be in the global scope, not to your viewmodel. Your first mistake is forgetting to define self in your FoodVM. This.FoodsList = ko.observableArray() Ĭould you please tell me where is my mistake?
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