Annotated Callback Methods

A talk that I gave on 2/20 for my class on design patterns. Trying new slide design and presentation style.

Transcript

1. Annotated Callback Methods
2. Huh?
3. Huh? It’s really cool, Actually.
4. Motivation Conveniently register callback methods
5. The usual way: Anonymous classes addItem.addSelectionListener(new SelectionAdapter() { public void widgetSelected(SelectionEvent e) { // add button pressed, handle its event } });
6. But that’s a pain when you have lots of callbacks.
7. What about a method to “register” callbacks as part of an interface?
8. What about a method to “register” callbacks as part of an interface?
9. Annotated Callback Methods
10. Annotations! “decorators” in Python
11. Example public class SomePlugin { @Event.ButtonPressed public void pressed(PressedEvent e) { // … handle the button press event } }
12. Good Stuff Name your methods whatever you want
13. Good Stuff Dynamic, great for “plugins”
14. Good Stuff No need to register callbacks elsewhere
15. Not-so-good Stuff Tools hate it: Refactoring, finding uses, etc.
16. Not-so-good Stuff Java compiler can’t verify parameters and return types
17. Not-so-good Stuff Class providing callbacks depends on annotation interface
18. Real World Application
19. Real World Application (a python web microframework)
20. from flask import Flask app = Flask(__name__) @app.route("/") def hello(): return "Hello World!" if __name__ == "__main__": app.run()
21. My Example
22. My Example An IRC Bot
23. My Example An IRC Bot
24. Resources • Annotated Callback Methods (http://slesinsky.org/brian/code/annotated_callback.html) • Flask (http://flask.pocoo.org/) • Personal Experience (seeing the pattern used in the real world)
25. Questions?