Alternatives on passing parameters from ViewModel to ViewModel in MvvmCross

Question

We are at the preparation on porting a huge windows mobile app to Xamarin and we are using MvvmCross to help us with the Mvvm.

The application is huge, where workflows live between several pages. So there is a need to pass states/objects between pages. As those states can be big, it does not make sense to serialise them between navigation calls.

My question is: what are any proven or used alternatives to pass objects between view models? Is there some session manager?

Note: we are starting with Android, so maybe there is also good an Android only solution.

Hint: I posted this question on Programmers as well, not sure what's the better platform for this: https://softwareengineering.stackexchange.com/questions/285219/alternatives-on-passing-parameters-from-viewmodel-to-viewmodel-in-mvvmcross

Answer 1

A couple of options I use are:

1) Persist state to a SQLite database and pass an identifier from ViewModel to ViewModel. This is simple and ensures that the state remains even between app restarts.

2) Another option, which is useful in a wizard-like setting is to use a Cache service. I simply created an interface to add and remove entries in a cache by key. I treat it like a standard MvvmCross service and use IoC to inject into my view models. At the start of the process, create a GUID to use as your key, add your state to the cache. Simply pass the key to the next view model, where it can retrieve the state from cache.