Explanation of the metaprogramming in Ruby getting started

Some people said that the ninth chapter of the metaprogramming routines are not easy to understand. I apologize for the lack of ability to show all aspects of metaprogramming, so I chose to demonstrate the simplest metaprogramming without explaining it.

Below are some comments of the routine, which cannot be understood. For beginners, you know that Ruby is longer than metaprogramming.

Ruby code

2. ClassMetaperson
4. DefMetaperson. method_missing (methodname, * ARGs) # redefine the ruby built-in method method_missing
5. Name = methodname. to_s
6. Begin
7. # Call the built-in Ruby method class_eval to automatically generate a new method
8. Class_eval (% Q [
9. Def# {Name}
10. Puts '# {name}, # {name}, # {name }...'
11. End
12. ])
13. Rescue
14. # When an exception occurs, execute the original Ruby method_missing (methodname, * ARGs)
15. Super(Methodname, * ARGs)
16. End
17. End
19. DefMethod_missing (methodname, * ARGs)
20. Metaperson. method_missing (methodname, * ARGs) # instance method_missing call class method method_missing
21. Send (methodname) # Use the ruby built-in send method to call the previously automatically generated Method
22. End
24. # The following code is similar ---------
25. DefMetaperson. modify_method (methodname, methodbody)
26. Class_eval (% Q [
27. Def# {Methodname}
28. # {Methodbody}
29. End
30. ])
31. End
33. DefModify_method (methodname, methodbody)
34. Metaperson. modify_method (methodname, methodbody)
35. End
36. #---------------------------
37. End# End metaperson class definition
39. ClassPerson <metaperson
40. End
42. Person1 = person.New
43. Person2 = person.New
45. Person1.sleep # => sleep, sleep, sleep...
46. Person1.running # => running, running, running...
48. Person1.modify _ method ("Sleep", "puts 'zzz... '") # modify the method sleep
49. Person1.sleep # => Zzz...
50. Person2.sleep # => Zzz...

 

What is the purpose of this routine?

Assume that an nd5 robot in "mechanical Public Enemy" finds that smiling is a good communication behavior during the implementation of "Protection of Human Beings", and thus smile. Although nd5 robots would not be smile before, all nd5 robots could be smile just as soon as an nd5 robot tried smile. Of course, any nd5 robot can evolve smile in the future and share the evolution of smile with other nd5 robots.

Maybe you don't want every nd5 robot to be smile. You like the maverick behavior of an instance object. For example, Sanny and Sanny are really different, strong, and witty, humble (please allow me to use these adjectives on a robot ).

To meet your requirements, try the following program.

Ruby code

1. ClassPerson
3. DefMethod_missing (methodname, * ARGs)
4. Name = methodname. to_s
5. OBJ =Self. Inspect
6. Begin
7. Self. Instance_eval (% Q [
8. Def# {Name}
9. Puts '# {OBJ}, # {name }'
10. End
11. ])
12. Send (methodname)
13. Rescue
14. Super(Methodname, * ARGs)
15. End
16. End
18. DefModify_method (methodname, methodbody)
19. Self. Instance_eval (% Q [
20. Def# {Methodname}
21. # {Methodbody}
22. End
23. ])
24. End
26. End
28. P1 = person.New
29. P2 = person.New
31. P1.sleep #=># <person: 0x296cb14>, sleep
32. P1.modify _ method (: Sleep, "puts 'this is P1 Zzz ...'")
33. P1.sleep # => This is P1 Zzz...
35. P2.sleep #=># <person: 0x296c998>, sleep
36. P2.modify _ method (: Sleep, "puts 'this is P2 Zzz ...'")
37. P2.sleep # => This is P2 Zzz...