Hi, I'm not saying that I don't agree with you but most of the problems you mention below are related to the models you use, PropertyModel and CompoundPropertyModel, not to the generics of form components. Check https://github.com/wicketstuff/core/wiki/LazyModel. You may see some improvements in compilation help.
On Thu, May 30, 2013 at 10:37 PM, tetsuo <[email protected]> wrote: > -1000! > > This will be horrible! Even with the current API, most generics I have to > declare in my code don't add anything to type safety. For example: > > add(new Form<Person>("form", new CompoundPropertyModel<Person>(new > PropertyModel<Person>(this, "person"))) > .add(new TextField<String>("name")) > .add(new TextField<Integer>("age")) > .add(new TextField<Double>("salary")) > .add(new Button("save", new PropertyModel<Person>(this,"person")){ > public void onSubmit() { > repository.save((Person)getForm().getDefaultModelObject()); > } > }); > > In my experience, this kind of code is fairly common in Wicket > applications. Every form component must be declared with a type, but none > has *any* kind of type safety gain. > > - The property model uses reflection, so its type can't be verified by the > compiler (this.person could be anything, not just a Person). > - Generics will guarantee that the form model will be of type Person, but > since it's all declared inline, and the real model isn't verifiable, it > just adds lots of verbosity without any real gain. > - Most form components use the implicit model, that also uses reflection, > and also can't verify the actual type of the underlying property, at > compilation time. Even in runtime, *the type information is lost due > erasure > *, so it can't use it to do any additional verification. > *- Worse, you can even declare the "name" TextField as <Integer> or > <Double> (while maintaining the 'text' attribute as String), and since > there is no type information at runtime, it doesn't matter. It won't even > throw an exception (it will just work normally).* In this case, the type > declaration is simply a lie. > > Just pain, no gain. In my code, I sometimes just add a @SuppressWarnings( > "rawtypes") to the class, and remove all useless generic type declarations. > If everything will be required to declare them, I will have do it more > frequently. > > That said, repeater components benefit greatly from generics. So do custom > models, validators, and converters. Or the rare cases that we explicitly > declare the form component model. But forcing everything to be > generic-typed will just make Wicket extremely verbose to use, with very > little benefit. > > > > > On Thu, May 30, 2013 at 4:00 AM, Martin Grigorov <[email protected] > >wrote: > > > Hi, > > > > I just pushed some initial work for [1] and [2] in > > branch generified-component-4930. > > > > So far it doesn't look nice. > > > > The added generics break somehow setMetaData/getMetaData methods - you > can > > see compilation errors in Component and Page classes. I think it is > caused > > by the anonymous instance of MetaDataKey ( new MetaDataKey<T>(type) {} ). > > > > Also the visit*** methods do not compile at the moment, but even if we > find > > a way to fix their signature I think writing a visitor will become quite > > cumbersome. > > At the moment we have IVisitor > > and org.apache.wicket.util.iterator.AbstractHierarchyIterator which do > the > > same job. The Iterator API is supposed to be simpler to write for the > > users. Maybe we can drop IVisitor ... ?! > > > > I'd like to ask for help with this task. It is supposed to be the biggest > > API break for Wicket 7.0. My current feeling is that the end result won't > > be very pleasant for the user-land code. > > For example the application code will have to do something like: > > > > WebMarkupContainer<Void> wmc = new WebMarkupContainer<>("id") > > > > It is not that much but we have to decide whether we want it. > > But first let's try to fix the compilation problems. > > > > > > 1. https://issues.apache.org/jira/browse/WICKET-4930 (Add generics to > > o.a.w.Component) > > 2. > > > > > https://cwiki.apache.org/confluence/display/WICKET/Wicket+7.0+Roadmap#Wicket7.0Roadmap-Genericsfororg.apache.wicket.Component > > >
