Bind to action method - mvvmcross

Question

Is it possible to use a simple action method - just like with Caliburn.Micro - instead of a command with MvvmCross bindings?
Example:
public void Action()
{
Tip = 11;
}
<Button
android:text="Button"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="#+id/button1"
local:MvxBind="Click Action" />
It doesn't work out of the box, I tested that.
While I found a lot of samples about adding new target bindings, I didn't find a single one about adding a new source binding.
UPDATE:
This works now out of the box with the Rio binding. To use it, add the MvvmCross MethodBinding NuGet package to the Android project.

Answer 1

Up until now, much of the emphasis for MvvmCross has been on allowing multi-platform target binding with the source remaining mainly 'vanilla' INotifyPropertyChanged.
There have been some deviation in terms of ViewModel structure - e.g.:
the MvxCommandCollection - http://slodge.blogspot.co.uk/2013/03/fixing-mvvm-commands-making-hot-tuna.html
some users using Fody - http://twincoders.com/blog/codigo-limpio-con-fody/
Recently, several new feature requests have also been logged in this area:
AutoCommands - I think this is what you are asking about here - https://github.com/slodge/MvvmCross/issues/301
Rio binding sources - https://github.com/slodge/MvvmCross/issues/299
Tibet binding - https://github.com/slodge/MvvmCross/issues/298
Because of these, I do expect more functionality to be exposed in this area in the future...
With that said, if you wanted to get this working today, then MvvmCross Binding is overrideable so you could fairly easily do it:
1. Implement an ICommand that invokes a MethodInfo using reflection (for completeness this should probably also use a parameter if available) - some kind of InvokeMethodCommand (code for this left to the reader!)
.
2. Implement an MyMethodSourceBinding class which wraps the InvokeMethodCommand - something like:
public class MyMethodSourceBinding : MvxSourceBinding
{
private readonly MethodInfo _methodInfo;
protected MyMethodSourceBinding(object source, MethodInfo methodInfo)
: base(source)
{
_methodInfo = _methodInfo;
}
public override void SetValue(object value)
{
// do nothing - not allowed
}
public override Type SourceType
{
get { return typeof(ICommand); }
}
public override bool TryGetValue(out object value)
{
value = new InvokeMethodCommand(source, _methodInfo);
return true;
}
}
3. Override MvvmCross's registered IMvxSourceBindingFactory with your own implementation that can detect when a method is present - sadly most of this is cut and paste coding today - it would be something like
public class MySourceBindingFactory
: IMvxSourceBindingFactory
{
private IMvxSourcePropertyPathParser _propertyPathParser;
private IMvxSourcePropertyPathParser SourcePropertyPathParser
{
get
{
if (_propertyPathParser == null)
{
_propertyPathParser = Mvx.Resolve<IMvxSourcePropertyPathParser>();
}
return _propertyPathParser;
}
}
public IMvxSourceBinding CreateBinding(object source, string combinedPropertyName)
{
var tokens = SourcePropertyPathParser.Parse(combinedPropertyName);
return CreateBinding(source, tokens);
}
public IMvxSourceBinding CreateBinding(object source, IList<MvxPropertyToken> tokens)
{
if (tokens == null || tokens.Count == 0)
{
throw new MvxException("empty token list passed to CreateBinding");
}
var currentToken = tokens[0];
if (tokens.Count == 1)
{
return CreateLeafBinding(source, currentToken);
}
else
{
var remainingTokens = tokens.Skip(1).ToList();
return CreateChainedBinding(source, currentToken, remainingTokens);
}
}
private static MvxChainedSourceBinding CreateChainedBinding(object source, MvxPropertyToken propertyToken,
List<MvxPropertyToken> remainingTokens)
{
if (propertyToken is MvxIndexerPropertyToken)
{
return new MvxIndexerChainedSourceBinding(source, (MvxIndexerPropertyToken) propertyToken,
remainingTokens);
}
else if (propertyToken is MvxPropertyNamePropertyToken)
{
return new MvxSimpleChainedSourceBinding(source, (MvxPropertyNamePropertyToken) propertyToken,
remainingTokens);
}
throw new MvxException("Unexpected property chaining - seen token type {0}",
propertyToken.GetType().FullName);
}
private static IMvxSourceBinding CreateLeafBinding(object source, MvxPropertyToken propertyToken)
{
if (propertyToken is MvxIndexerPropertyToken)
{
return new MvxIndexerLeafPropertyInfoSourceBinding(source, (MvxIndexerPropertyToken) propertyToken);
}
else if (propertyToken is MvxPropertyNamePropertyToken)
{
//**************************
// Special code is here
var propertyToken = (MvxPropertyNamePropertyToken) propertyToken;
if (source != null)
{
var method = source.GetType().GetMethod(propertyToken.PropertyName, BindingFlags.FlattenHierarchy | BindingFlags.Public | BindingFlags.Instance);
if (method != null)
{
return new MyMethodSourceBinding(source, method);
}
}
return new MvxSimpleLeafPropertyInfoSourceBinding(source,
(MvxPropertyNamePropertyToken) propertyToken);
// Special code ends here
//**************************
}
else if (propertyToken is MvxEmptyPropertyToken)
{
return new MvxDirectToSourceBinding(source);
}
throw new MvxException("Unexpected property source - seen token type {0}", propertyToken.GetType().FullName);
}
}
4. Supply this source binding factory in your own custom binding builder - e.g.:
public class MyAndroidBindingBuilder
: MvxAndroidBindingBuilder
{
protected override IMvxSourceBindingFactory CreateSourceBindingFactory()
{
return new MvxSourceBindingFactory();
}
}
5. Supply this binding builder during your setup
public class Setup : MvxAndroidSetup
{
// ....
protected override MvxAndroidBindingBuilder CreateBindingBuilder()
{
return new MyAndroidBindingBuilder();
}
}
Note: This approach is only for advanced users right now... As suggested in the first part of this question, I do expect the code in this area to change quite a lot so you might also encounter some issues maintaining a fork in this area. (Indeed the code in this area has already changed quite significantly on the Tibet Binding branch within the GitHub repo!)