Combobox model='xxx' whcih is not ListModel

asked 2013-08-13 18:44:44 +0800

phdsong gravatar image phdsong
13 3

updated 2013-08-14 14:58:44 +0800

I see many examples with List<String> xxx object is used in Zul code.

<Combobox model='xxx' />

I checked Combobox.java and see setModel signature as follows:

public void setModel(ListModel<?> model) {

I am not very clear how List<String> converts to ListModel when the model is set to Combobox object. I believe some behind-the-scene operations converts List<Sometype> object to ListModel<Sometype>. Can you explain how it works?

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answered 2013-08-14 06:19:33 +0800

sjoshi gravatar image sjoshi flag of India
3493 1 8

See if this zk-combobox-with-item-rendered will help to understand it.

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I guess Renderer is kicked in to convert them. So, when a list of object is passed, is each object from the list converted to Comboitem through render method?

phdsong ( 2013-08-14 15:03:58 +0800 )edit

answered 2013-08-14 18:52:11 +0800

phdsong gravatar image phdsong
13 3

updated 2013-08-14 20:35:50 +0800

This seems to explain why List<string> works good for model.

http://books.zkoss.org/wiki/ZK_Developer's_Reference/MVC/View/Renderer/Combobox_Renderer (Combobox Renderer)

When a combobox is assigned with a model, a default renderer is assigned too. The default renderer will assume that the combobox displays the data as a string. If you want to display more sophisticated information or retrieve a particular field of the data, you have to implement ComboitemRenderer to handle the rendering.

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answered 2013-08-14 20:41:25 +0800

phdsong gravatar image phdsong
13 3

updated 2013-08-14 20:43:39 +0800

I was a little bit confused about the question. Now, I realize that this is binding/annotation question.

From ZK http://www.zkoss.org/zkdemo/combobox/simple_combobox (Example)

ViewModel is as follows:

public class ShirtViewModel {

public List<String> getColors() {
    return ShirtData.getColors();

ZUL code

               <combobox id="cmbColor" width="150px"
                model="@load(vm.colors)" selectedItem="@bind(vm.shirtColor)">
                <template name="model">
                    <comboitem label="@load(each)"
                        image="@load(vm.getIconImage(each))" />

I believe the zul code, @load(vm.colors) whose colors from List<String> getColors(), manages convert List<String> to ListModel<String>. I think Binder kicks in to call some methods to convert them. Anyone knows what part of code does the job?

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answered 2013-08-14 21:35:45 +0800

phdsong gravatar image phdsong
13 3

Annotation Attributes - CONVERTER

http://books.zkoss.org/wiki/ZK_Component_Reference/Annotation/Data_Binding (Data Binding)

It looks ComboboxModelConverter does its job. Method super.coerceToUi() does its job to convert List to ListModel.

    @SuppressWarnings({ "rawtypes", "unchecked" })
public Object coerceToUi(Object val, C comp, BindContext ctx) {
    if (val == null) {
        val = new ArrayList();
    ListModel model = null;
    if (val instanceof ListModel) {
        BindELContext.addModel(comp, val); //ZK-758. @see AbstractRenderer#addItemReference
        return val;
    } else if (val instanceof Set) {
        model =  new ListModelSet((Set)val, false);//ZK-1528, doesn't use live
    } else if (val instanceof List) {
        //ZK-1528, doesn't use live, 
        //user should use ListModel if he want to dynamically change inside element.
        model =  new ListModelList((List)val, false); 
    } else if (val instanceof Map) {
        model =  new ListModelMap((Map)val, false);//ZK-1528, doesn't use live
    } else if (val instanceof Object[]) {
        model =  new ListModelArray((Object[]) val, false);//ZK-1528, doesn't use live
    } else if ((val instanceof Class) && Enum.class.isAssignableFrom((Class)val)) {
        model =  new ListModelArray((Object[]) ((Class)val).getEnumConstants(), false);//ZK-1528, doesn't use live
    } else if (val instanceof GroupsModel) { //feature#2866506: Data Binding shall support GroupsModel with Listbox/Grid
        model =  GroupsListModel.toListModel((GroupsModel) val);
    } else {
        throw new UiException("Expects java.util.Set, java.util.List, java.util.Map, Object[], Enum Class, GroupsModel, or ListModel only. "+val.getClass());
            //      final Container container = new Container(model);

    final ListModel compModel = getComponentModel(comp);
    if(compModel instanceof Selectable){
        Selectable selectable = ((Selectable)compModel);
        ((Selectable) model).setMultiple(selectable.isMultiple());

        //Should we check the contains? it has O(m) issue and O(mn) in array case
        //if not, there is a issue if the new data doesn't contains the selected obj
                    //          for(Object selected:container.contains(selectable.getSelection())){
                    //              ((Selectable) model).addToSelection(selected);
                    //          }

        //no need to check contains, user should remove the selection if it is not in current list anymore
        //that could be done by binding to selectedItem or selectedItems
        for(Object selected:selectable.getSelection()){
            ((Selectable) model).addToSelection(selected);

    model = handleWrappedModel(ctx,comp,model);
    BindELContext.addModel(comp, model); //ZK-758. @see AbstractRenderer#addItemReference

    return model;
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Asked: 2013-08-13 18:44:44 +0800

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Last updated: Aug 14 '13

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