OnChangeAjaxBehavior on FormComponentPanel: model object is null

[Martin Dietze <di...@fh-wedel.de>]

I'v stumbled across something that is really puzzling me. In our
project a specific sort of inputs needs to be derived from
FormComponentPanel. One of these simply contains a
DropDownChoice<String> of which the model object is simply
passed through.

In some context I added an OnChangeAjaxBehavior to this
component and found that in its onChange() method the
component's model object is always null. Needless to say that if
I attach the behavior to the inner drop down element,
everything's fine, but this thing still seems wrong to me.

I believe I implemented the form component the right way (see
below). Now I am wondering, is what I do not supposed to work
anyway? Or is there anything else I need to take care of apart
from overriding convertInput() and extending onBeforeRender()?

I've created a quickstart project and appended it to this mail,
but for a quick look consider the way I implemented my selection
component:

|   private DropDownChoice<String> choice;
|
|    public NestedDropDown( String id, IModel<String> model ) {
|        super( id, model );
|        this.choice = new DropDownChoice<String>( "choice", model, Arrays.asList("Joe", "Patrick", "Ivan") );
|        add(this.choice);
|    }
|
|    @Override
|    protected void convertInput() {
|        setModelObject(this.choice.getModelObject());
|    }
|
|    @Override
|    protected void onBeforeRender() {
|        this.choice.setModelObject( getModelObject() );
|        super.onBeforeRender();
|    }

And it is used like this:

|    final IModel<String> model = new Model<String>("Nothing selected.");
|    final Label label = new Label("label", model);
|    label.setOutputMarkupId( true );
|    
|    final NestedDropDown nestedDropDown1 = new NestedDropDown( "dropDown1", Model.of( "Joe" ) );
|    nestedDropDown1.add( new OnChangeAjaxBehavior() {
|        private static final long serialVersionUID = 2645176698181954589L;
|        @Override
|        protected void onUpdate( AjaxRequestTarget target ) {
|            model.setObject(nestedDropDown1.getModelObject());
|            target.add( label );
|        }
|    } );

Any hint appreciated!

M'bert

-- 
----------- / http://herbert.the-little-red-haired-girl.org / -------------
=+= 
My family says I'm a psychopath, but the voices in my head disagree

Re: OnChangeAjaxBehavior on FormComponentPanel: model object is null

[Sven Meier <sv...@meiers.net>]

You have to attach an AjaxFormComponentUpdatingBehavior to the actual 
FormComponent that is bound to the <input> tag.
Otherwise no value will be sent to the server.

Sven


On 07/10/2013 03:00 PM, Martin Dietze wrote:
> I'v stumbled across something that is really puzzling me. In our
> project a specific sort of inputs needs to be derived from
> FormComponentPanel. One of these simply contains a
> DropDownChoice<String> of which the model object is simply
> passed through.
>
> In some context I added an OnChangeAjaxBehavior to this
> component and found that in its onChange() method the
> component's model object is always null. Needless to say that if
> I attach the behavior to the inner drop down element,
> everything's fine, but this thing still seems wrong to me.
>
> I believe I implemented the form component the right way (see
> below). Now I am wondering, is what I do not supposed to work
> anyway? Or is there anything else I need to take care of apart
> from overriding convertInput() and extending onBeforeRender()?
>
> I've created a quickstart project and appended it to this mail,
> but for a quick look consider the way I implemented my selection
> component:
>
> |   private DropDownChoice<String> choice;
> |
> |    public NestedDropDown( String id, IModel<String> model ) {
> |        super( id, model );
> |        this.choice = new DropDownChoice<String>( "choice", model, Arrays.asList("Joe", "Patrick", "Ivan") );
> |        add(this.choice);
> |    }
> |
> |    @Override
> |    protected void convertInput() {
> |        setModelObject(this.choice.getModelObject());
> |    }
> |
> |    @Override
> |    protected void onBeforeRender() {
> |        this.choice.setModelObject( getModelObject() );
> |        super.onBeforeRender();
> |    }
>
> And it is used like this:
>
> |    final IModel<String> model = new Model<String>("Nothing selected.");
> |    final Label label = new Label("label", model);
> |    label.setOutputMarkupId( true );
> |
> |    final NestedDropDown nestedDropDown1 = new NestedDropDown( "dropDown1", Model.of( "Joe" ) );
> |    nestedDropDown1.add( new OnChangeAjaxBehavior() {
> |        private static final long serialVersionUID = 2645176698181954589L;
> |        @Override
> |        protected void onUpdate( AjaxRequestTarget target ) {
> |            model.setObject(nestedDropDown1.getModelObject());
> |            target.add( label );
> |        }
> |    } );
>
> Any hint appreciated!
>
> M'bert
>
>
>
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