Basic introduction to ruby metaprogramming. Big thanks to Dave Thomas for his tutorials on metaprogramming

1. Beauty of
Metaprogramming
in Ruby
S. M. Ashif Manjur
@Nascenia

2. • What is Metaprogramming?
• Ruby Object Model
• Sharing functionalities
• instance_eval and class_eval
• Magic of method_missing
Topics I will touch…

3. “Writing code that writes code”
WHAT IS METAPROGRAMMING?

4. METHOD LOOKUP CHAIN

5. • Classes are always open
• Class definitions are live
• Classes are objects
• Every method call has a
receiver
• Anonymous or ghost classes
CLASSES

6. CONSOLE OUTPUT: $$$ CAR
OPEN CLASSES

7. “with great power comes great
responsibility”
AS UNCLE BEN SAYS…

8. CONSOLE OUTPUT: $$$ CAR
MONKEY PATCHING

9. DEFINITIONS ARE LIVE

10. CLASSES ARE OBJECTS

11. SELF AS A RECEIVER

12. SINGLETON METHODS

13. GHOST CLASSES

14. CLASS METHODS ARE SAME

15. • Prototype
• Inheritance
• Mixin
SHARING FUNCTIONALITY

16. PROTOTYPE

17. INHERITANCE

18. MIXIN

19. AFTER MIX(ED) IN…

20. EVALS ARE EVIL

21. instance_eval

22. class_eval

23. METHOD MISSING

24. Q&A

25. THANK YOU