FreshMvvm.Maui

If you're looking for .NET MAUI version of FreshMvvm, aka FreshMvvm.Maui then please visit: https://github.com/XAM-Consulting/FreshMvvm.Maui

FreshMvvm for Xamarin.Forms

FreshMvvm is a super light Mvvm Framework designed specifically for Xamarin.Forms. It's designed to be Easy, Simple and Flexible.

How does it compare to other options?

• It's super light and super simple
• It's specifically designed for Xamarin.Forms
• Designed to be easy to learn and develop (great when you are not ready for RxUI)
• Uses a Convention over Configuration

Features

• PageModel to PageModel Navigation
• Automatic wiring of BindingContext
• Automatic wiring of Page events (eg. appearing)
• Basic methods (with values) on PageModel (init, reverseinit)
• Built in IOC Container
• PageModel Constructor Injection
• Basic methods available in Model, like Alert
• Built in Navigation types for SimpleNavigation, Tabbed and MasterDetail

Note ~~Different to standard naming conventions, FreshMvvm uses Page and PageModel instead of View and ViewModel, this is inline with Xamarin.Forms using Pages~~ Now we can use both the ViewModel naming conventions.

The Story

I (Michael Ridland) was part-way into a Xamarin Traditional application when Xamarin.Forms was released. I wanted to move the project onto Xamarin.Forms but on that project I was using MvvmCross. At that time MvvmCross had no support for Xamarin.Forms, so I had the option of 1) adapting MvvmCross, 2) finding an alternative or 3) rolling my own Mvvm. The best part about MvvmCross was it's two-way databinding to the native iOS/Android controls but since Xamarin.Forms already had the Databinding builtin, that wasn't useful and the size with MvvmCross was an overhead when I didn't require it. I also wasn't able to find an alternative that I could easily move to. So that I could keep it simple and flexible, I ended up rolling my own Mvvm.

It's grown up from this post on rolling your own Mvvm for Xamarin.Forms. I try hard to keep the simplicity of rolling your own Mvvm for Xamarin.Forms.

It was never a plan to create a framework but after presenting my Mvvm solution at a few events, I found many people wanted it and seemed to be really interested in it. Also considering I've been using this Framework in all my projects from the start of Xamarin.Forms I know that it works, so I created FreshMvvm and that's how it was born.

Conventions

This Framework, while simple, is also powerful and uses a Convention over Configuration style.

Note ~~Different to standard naming conventions, FreshMvvm uses Page and PageModel instead of View and ViewModel, this is inline with Xamarin.Forms using Pages~~ Now we can use both the ViewModel naming conventions.

• A Page must have a corresponding PageModel, with naming important so a QuotePageModel must have a QuotePage The BindingContext on the page will be automatically set with the Model
• A PageModel can have a Init method that takes a object
• A PageModel can have a ReverseInit method that also take a object and is called when a model is poped with a object
• PageModel can have dependancies automatically injected into the Constructor

Navigation

The Primary form of Navigation in FreshMvvm is PageModel to PageModel, this essentially means our views have no idea of Navigation.

So to Navigate between PageModels use:

await CoreMethods.PushPageModel<QuotePageModel>(); // Pushes navigation stack
await CoreMethods.PushPageModel<QuotePageModel>(null, true); // Pushes a Modal
await CoreMethods.PushPageModel<QuotePageModel> (pm => pm.Quote = "Quote 23") // Pushes Navigation Stack and initializes the property 'Quote' with  value 'Quote 23'

The engine for Navigation in FreshMvvm is done via a simple interface, with methods for Push and Pop. Essentially these methods can control the Navigation of the application in any way they like.

public interface IFreshNavigationService
{
	Task PushPage(Page page, FreshBasePageModel model, bool modal = false);
	Task PopPage(bool modal = false);
}

Within the PushPage and PopPage you can do any type of navigation that you like, this can be anything from a simple navigation to a advanced nested navigation.

The Framework contains some built in Navigation containers for the different types of Navigation.

Basic Navigation - Built In

var page = FreshPageModelResolver.ResolvePageModel<MainMenuPageModel> ();
var basicNavContainer = new FreshNavigationContainer (page);
MainPage = basicNavContainer;

Master Detail - Built In

var masterDetailNav = new FreshMasterDetailNavigationContainer ();
masterDetailNav.Init ("Menu");
masterDetailNav.AddPage<ContactListPageModel> ("Contacts", null);
masterDetailNav.AddPage<QuoteListPageModel> ("Pages", null);
MainPage = masterDetailNav;

Tabbed Navigation - Built In

var tabbedNavigation = new FreshTabbedNavigationContainer ();
tabbedNavigation.AddTab<ContactListPageModel> ("Contacts", null);
tabbedNavigation.AddTab<QuoteListPageModel> ("Pages", null);
MainPage = tabbedNavigation;

Implementing Custom Navigation

It's possible to setup any type of Navigation by implementing IFreshNavigationService.There's a sample of this in Sample Application named CustomImplementedNav.cs.

Sample Apps

• Basic Navigation Sample
• Tabbed Navigation Sample
• MasterDetail Navigation Sample
• Tabbed Navigation with MasterDetail Popover Sample (This is called the CustomImplementedNav in the Sample App)

Inversion of Control (IOC)

So that you don't need to include your own IOC container, FreshMvvm comes with a IOC container built in. It's using TinyIOC underneith, but with different naming to avoid conflicts.

To Register services in the container use Register:

FreshIOC.Container.Register<IDatabaseService, DatabaseService>();

To obtain a service use Resolve:

FreshIOC.Container.Resolve<IDatabaseService>();

*This is also what drives constructor injection.

IOC Container Lifetime Registration Options

We now support a fluent API for setting the object lifetime of object inside the IOC Container.

// By default we register concrete types as 
// multi-instance, and interfaces as singletons
FreshIOC.Container.Register<MyConcreteType>(); // Multi-instance
FreshIOC.Container.Register<IMyInterface, MyConcreteType>(); // Singleton 

// Fluent API allows us to change that behaviour
FreshIOC.Container.Register<MyConcreteType>().AsSingleton(); // Singleton
FreshIOC.Container.Register<IMyInterface, MyConcreteType>().AsMultiInstance(); // Multi-instance

As you can see below the IFreshIOC interface methods return the IRegisterOptions interface.

public interface IFreshIOC
{
    object Resolve(Type resolveType);
    IRegisterOptions Register<RegisterType>(RegisterType instance) where RegisterType : class;
    IRegisterOptions Register<RegisterType>(RegisterType instance, string name) where RegisterType : class;
    ResolveType Resolve<ResolveType>() where ResolveType : class;
    ResolveType Resolve<ResolveType>(string name) where ResolveType : class;
    IRegisterOptions Register<RegisterType, RegisterImplementation> ()
        where RegisterType : class
        where RegisterImplementation : class, RegisterType;
}

The interface that's returned from the register methods is IRegisterOptions.

public interface IRegisterOptions
{
    IRegisterOptions AsSingleton();
    IRegisterOptions AsMultiInstance();
    IRegisterOptions WithWeakReference();
    IRegisterOptions WithStrongReference();
    IRegisterOptions UsingConstructor<RegisterType>(Expression<Func<RegisterType>> constructor);
}

PageModel - Constructor Injection

When PageModels are pushed services that are in the IOC container can be pushed into the Constructor.

FreshIOC.Container.Register<IDatabaseService, DatabaseService>();

PageModel Important Methods

/// <summary>
/// The previous page model, that's automatically filled, on push
/// </summary>
public FreshBasePageModel PreviousPageModel { get; set; }

/// <summary>
/// A reference to the current page, that's automatically filled, on push
/// </summary>
public Page CurrentPage { get; set; }

/// <summary>
/// Core methods are basic built in methods for the App including Pushing, Pop and Alert
/// </summary>
public IPageModelCoreMethods CoreMethods { get; set; }    

/// <summary>
/// This method is called when a page is Pop'd, it also allows for data to be returned.
/// </summary>
/// <param name="returndData">This data that's returned from </param>
public virtual void ReverseInit(object returndData) { }

/// <summary>
/// This method is called when the PageModel is loaded, the initData is the data that's sent from pagemodel before
/// </summary>
/// <param name="initData">Data that's sent to this PageModel from the pusher</param>
public virtual void Init(object initData) { }

/// <summary>
/// This method is called when the view is disappearing. 
/// </summary>
protected virtual void ViewIsDisappearing (object sender, EventArgs e)
{
}

/// <summary>
/// This methods is called when the View is appearing
/// </summary>
protected virtual void ViewIsAppearing (object sender, EventArgs e)
{
}

The CoreMethods

Each PageModel has a property called 'CoreMethods' which is automatically filled when a PageModel is pushed, it's the basic functions that most apps need like Alerts, Pushing, Poping etc.

public interface IPageModelCoreMethods
{
	Task DisplayAlert (string title, string message, string cancel);
	Task<string> DisplayActionSheet (string title, string cancel, string destruction, params string[] buttons);
	Task<bool> DisplayAlert (string title, string message, string accept, string cancel);
	Task PushPageModel<T>(object