Overriding the view lookup convention used in MvvmCross

Following on from a question on StackOverflow - http://stackoverflow.com/questions/14147614/mvvmcross-navigation-issue-getting-exception-could-not-find-view-for-viewmode

If ever you want to override the default viewmodel-view lookup setup, then you can do so by overriding the GetViewModelViewLookup method in your Setup class.

The default lookup table is generated by:

• enumerating all the Types in the Setup.cs Assembly
• removing any which don't implement IMvx-platform-View
• removing any which are abstract
• removing any which start/end with the word Base
• removing any which are marked with the Unconventional attribute
• removing any which are marked with the ConditionalConventional attribute and who's condition fails (this is used for e.g. iPad vs iPhone selection - see Sharing ViewModels for different Views)
• finding the ViewModel property on each remaining Type
• removing any who's ViewModel PropertyType starts/ends with the word Base
• removing any who's ViewModel PropertyType is an interface
• listing the remaining {ViewModel PropertyType, View Type} as a Dictionary lookup.

If you wish to replace this algorithm, you can - just override GetViewModelViewLookup

For example, at a trivial level, you could just hard code the ViewModel-View list:

	protected override IDictionary<Type, Type> GetViewModelViewLookup()
	{
	return new Dictionary<Type,Type>()
	{
	{ typeof(LoginViewModel), typeof(LoginActivity) },
	{ typeof(HomeViewModel), typeof(HomeActivity) } ,
	{ typeof(DetailViewModel), typeof(DetailActivity) },
	{ typeof(UploadViewModel), typeof(UploadActivity) }
	};
	}

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This hard-coded list is actually what the very first versions of MvvmCross did - and it does have a small performance advantage - it makes app startup a bit quicker.


For a slightly more complicated example, you could generate an alternative list based on several assemblies, and could then supplement that list with some conditional logic:

	public List<Assembly> MyViewAssemblies { get; set; }
	protected override IDictionary<System.Type, System.Type> GetViewModelViewLookup()
	{
	var toReturn = new Dictionary<Type, Type>();
	foreach (var assembly in MyViewAssemblies)
	{
	var contributions = base.GetViewModelViewLookup(assembly, typeof (IMvxAndroidView));
	foreach (var kvp in contributions)
	{
	toReturn[kvp.Key] = kvp.Value;
	}
	}
	if (SomeCondition)
	{
	toReturn[typeof(SpecialViewModel)] = typeof(SpecialView1);
	}
	else
	{
	toReturn[typeof(SpecialViewModel)] = typeof(SpecialView2);
	toReturn[typeof(AnotherSpecialViewModel)] = typeof(AnotherSpecialView3);
	}
	return toReturn;
	}

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