AssemblableTypes

From APIDesign

Revision as of 19:30, 8 May 2011

By splitting APIs into multiple modules one increases their flexibility. The API become independent and can be used in new contexts, without the rest of the APIs being present. However one also complicates the usage, as for some, original (in case the API used to be present as a whole) usecases, the users need to try harder to make the APIs work together. That is indeed not good (as it increases Time To Market). This article describes one of my advantures where I had to deal with similar situation.

Setup

There are following modules In the NetBeans APIs:

• Text API - contains class like CloneableEditorSupport.Pane and some of its implementations and can open editor for any source of characters
• MultiView API - depends on Text API and provides another implementation of the pane which can be created by MultiViewFactory.
• Loaders API - which depends on Text API and connects it with real files on disk via functionality provided by DataObject.

Users of the NetBeans API People often create their own DataObject implementations to represent textual data. Good, there is support for that in the Loaders API. There is however common requirement to show not only editor, but also other view, e.g. to use MultiView API.

However Loaders API knows nothing about MultiView API and MultiView API knows nothing about Loaders API. Their only common dependency is the Text API. Can I write a wizard to generate simple, maintainable code that defines DataObject represented by few MultiViewElements including one for text editor?

History

The common style to achieve this is to create a new, AbstractedTypes and put them into new module that both text and loaders API will depend on. This works fine, but requires creation of whole new API module. In my case that was not really appropriate. Any other option?

Improvements

Interesting new possibility is to use Java generics. Instead of abstracting the common interface (that text and loaders API needs), one can enumerate a set of common interfaces comming for example from JDK and require them all:

<T extends Runnable & Callable & PropertyChangeListener> int myMethod(T multiType);

This is gettting closer to the style of functional programming as pioneered by Haskell (or Clean). Define a lot of abstract categories (in their terminology classes, but don't confuse that with OOP classes) and then use these categories to define appropriate type for each function/method.

In case one can find good enough types in the base, this kind of on the fly creation of types is usually more flexible.

Result

TBD