Xamarin: MVVMCross info

Question

Adapting the MVVMCross framework in Xamarin crossplatform application development, we have PCL (containing Model and View Model) and View (for each platform) as in here.

a) Where does the Xamarin.mobile (for gaining single set of API access) reside? I think inside the PCL. But, i see different binaries for Xamarin.mobile (eg: Android and IOS), do we put all the Xamarin.mobile library inside the PCL? They all have the same name, won't there be any conflict?

b) Where do we keep codes like accessing bluetooth (not available in Xamarin.mobile)? Using MVVMCross decouples the view and business logic, so do all the codes for creating view items after an event has occured (btn click), reside in the view?

c) Where can we use the conditional compilation adapting MVVMCross? I guess in the Model, but is it only used for file access or can it also be used to show view items (toast message on Android) according to the target platform, by placing it on the PCL?

(Excuses if inappropriate, just gathered some information on MVVMCross and Xamarin.mobile and had some reasonings/confusions in mind)

Thank You!

Regards, Saurav

Answer 1

a) Where does the Xamarin.mobile (for gaining single set of API access) reside? I think inside the PCL. But, i see different binaries for Xamarin.mobile (eg: Android and IOS), do we put all the Xamarin.mobile library inside the PCL? They all have the same name, won't there be any conflict?

Xamarin.Mobile is not portable code - it can't be called directly from PCLs.

For many Xamarin.Mobile functions (and many, many functions which Xamarin.Mobile does not cover) then MvvmCross provides Plugins - you can see some of that in https://www.nuget.org/packages?q=mvvmcross

For the remaining few methods that X.M has but we haven't already included - e.g. contacts lookup - then you can either:

• access the Xamarin.Mobile functions by writing a portable interface (a facade) through which to access them
• write a new plugin to implement them

For more on plugins:

• see N=8 - adding the location plugin - from the N+1 videos in http://mvvmcross.wordpress.com/
• for writing a plugin see https://speakerdeck.com/cirrious/plugins-in-mvvmcross

b) Where do we keep codes like accessing bluetooth (not available in Xamarin.mobile)?

Generally this is done the same way as above. For example, for Bluetooth take a look at the Sphero example:

• http://blog.xamarin.com/xamarin-developer-showdown-winning-entries-showcase-xamarin-mobile/
• https://github.com/slodge/BallControl/tree/master/Cirrious.Sphero.WorkBench/Plugins/Sphero

Using MVVMCross decouples the view and business logic, so do all the codes for creating view items after an event has occured (btn click), reside in the view?

Yes - if it's a 'view concern', then it belongs in the view (this is the same as any Mvvm code)

c) Where can we use the conditional compilation adapting MVVMCross?

I try not to use 'conditional compilation' including #if and partial classes. Sometimes I'll use it in plugin platform-specific modules, but generally I try to use inheritance or abstraction instead - the reason for this is because I use tools like 'refactoring' and 'unit tests' a lot and conditional compilation simply does not work with these.

For more on the benefits (and disadvantages) of using PCLs rather than file-linking and other project-based techniques, see What is the advantage of using portable class libraries instead of using "Add as Link"?