Question

This code is from the Wicket in Action book.

    final WebMarkupContainer parent = new WebMarkupContainer("comments");
    parent.setOutputMarkupId(true);
    add(parent);
    List<String> comments = ...

    parent.add(new ListView("list", comments) {

        @Override
        protected void populateItem(ListItem item) {
            item.add(new Label("comment", item.getModel()));
        }
    });

    Form form = new Form("form");
    final TextArea editor = new TextArea("editor", new Model(""));
    editor.setOutputMarkupId(true);
    form.add(editor);
    form.add(new AjaxSubmitLink("save") {
        @Override
        protected void onSubmit(AjaxRequestTarget target, Form form) {
            comments.add(editor.getModelObjectAsString());
            editor.setModel(new Model(""));
            target.addComponent(parent);
            target.focusComponent(editor);
        }
    });
    parent.add(form);

It doesn’t compile. Inside the override method, the row

comments.add(editor.getModelObjectAsString());

generates the following errors in Eclipse

“Multiple markers at this line. Cannot refer to a non-final variable comments inside an inner class defined in a different method. The method getModelObjectAsString() is undefined for the type TextArea.”

I love programming books written by the authors of a framework with examples that don’t work =) seriously though, what is wrong here and how can it be fixed?

EDIT:

In order for it to compile in Wicket 1.4, the code needs to change to

    /* Java code */
    final WebMarkupContainer parent = new WebMarkupContainer("comments");
    parent.setOutputMarkupId(true);
    add(parent);
    final List<String> comments = new ArrayList<String>();

    parent.add(new ListView("list", comments) {

        @Override
        protected void populateItem(ListItem item) {
            item.add(new Label("comment", item.getModel()));
        }
    });

    Form form = new Form("form");
    //final TextArea editor = new TextArea("editor", new Model(""));
    final TextArea editor = new TextArea("editor", new Model(""));
    editor.setOutputMarkupId(true);
    form.add(editor);
    form.add(new AjaxSubmitLink("save") {
        @Override
        protected void onSubmit(AjaxRequestTarget target, Form form) {
            comments.add((String) editor.getModelObject());
            editor.setModel(new Model(""));
            target.addComponent(parent);
            target.focusComponent(editor);
        }
    });
    parent.add(form);

But if the list is made final, then wont it be impossible to dynamically alter its contents?

Answer 1

Putting my comment into a real answer:

The problem is the not the final on the TextArea, but that the Wicket in Action book is written for Wicket 1.3 and the APi has changed for version 1.4 / 1.5.

The migration guide for Wicket i.4 states that the members have been renamed to getDefaulModelXXX().

Have fun with wicket.