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In MVP pattern, a Presenter has an interface of View so the presenter can call iview.DoSomething().. What about in MVVM pattern?
According to John Gossman's UML diagram http://blogs.msdn.com/johngossman/archive/2006/04/13/576163.aspx , ViewModel doesn't have an interface of View. So, seems like the ViewModel and View should be communicated via Binding only. (or use attached property or blend behavior or etc).
What do you guys think?
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The ViewModel class is designed to store and manage UI-related data in a lifecycle conscious way. The ViewModel class allows data to survive configuration changes such as screen rotations.
Caution: A ViewModel must never reference a view, Lifecycle, or any class that may hold a reference to the activity context.
The view model is an abstraction of the view exposing public properties and commands. Instead of the controller of the MVC pattern, or the presenter of the MVP pattern, MVVM has a binder, which automates communication between the view and its bound properties in the view model.
What is a proper way to communicate between the ViewModel and the View , Google architecture components give use LiveData in which the view subscribes to the changes and update itself accordingly, but this communication not suitable for single events, for example show message, show progress, hide progress etc.
I agree with John Gossman. The way the ViewModel "talks" to the View is through Bindings only. In fact - the ViewModel shouldn't care about the View at all. It should simply make data available through properties, and it's up to the View to decide what it will dynamically bind to in the ViewModels. If the ViewModel wants to tell the View something this should occur implicit through Bindings.
A similar question was asked an hour ago - here.
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