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E4: A First Look
I've finally got some cycles to catch up on E4 a bit. The first thing I notice is that in E4, you wind up with a lot of code that looks something like this: (from http://www.vogella.de/articles/EclipseE4/article.html)
public class View1 { @Inject public View1(Composite parent) { Label label = new Label(parent, SWT.NONE); label.setText("E4 is new"); Text text = new Text(parent, SWT.NONE); text.setText("and different"); } }
The first thing I notice is the dependency injection: there's no explicit dependency on Eclipse anywhere to be seen.
I haven't worked out all the implications of that @Inject annotation, but at first blush this sort of thing would seem to make E4 *much* more testable than previous versions of Eclipse were.
If I'm right, this is pretty huge. It's not exactly a killer feature, but it's very important.
Thoughts?
Discussion
From the code above I would have no clue what is actually injected. The parent? Is the view injected somewhere? DI is certainly a good thing. But in that case its not obvious what the annotation does.
@Philipp In the example the Composite “parent” is injected. In chapter 6 of http://www.vogella.de/articles/EclipseE4/article.html you see examples of parameter injection which make it more explicit.
Hope this helps.
@Philipp: I checked http://www.vogella.de/articles/EclipseE4/article.html and it also explains that the composite it injected into the view.
Yes, dependency injection makes code much more testable. Especially in Eclipse-singleton-land
Not only is code like this easier to test, it is also easier to reuse in different contexts (in a dialog or wizard, in a standalone SWT application, etc).