And then there were Mixins

One of the key goals for my binding infrastructure has been to make it easy to extend the value models to suit your business requirements. The idea was let you define a custom value model properties and have the library automatically manage them. I had this working pretty well, but it was pretty painful to set up, and definitely not something I’d wish on others.

Enter Mixins. Somewhere along the line it occurred to me that I could create Mixins that provide standard ValueModel extensions and their handlers out of the box. The first test was to convert my ComponentValueModel interfaces that defines standard component properties such as enabled, editable and visible.

public interface ComponentValueModel extends ValueModel
    public boolean isEnabled();
    public void setEnabled(boolean enabled);

    public boolean isEditable();
    public void setEditable(boolean editable);

    public boolean isVisible();
    public void setVisible(boolean visible);

Using this mixin is now as simple as..

// install the mixin that defines the ComponentValueModel
// interface and standard handlers.

// create a presentation model that vends ComponentValueModels
pm = new BeanPresentationModel<Person, ComponentValueModel>(...);

// all the value models returned by the presentation model will 
// implement the mixin interface.
ComponentValueModel cvm = pm.get("firstName");
// changes to the mixin properties will be automatically handled 
// by the mixin

From here the mixin is responsible for updating the state of components bound to ComponentValueModels. The mixin uses styles that map particular model properties to particular components allowing you to control the way particular properties effect particular components.

So far I’m really pleased with the progress.

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