1.
Replacing
Conditionals With
Polymorphism
@gpespn

2.
“Any fool can write code that a
computer can understand.
Good programmers write code
that humans can understand.”
-- Martin Fowler
@gpespn

3.
@gpespn
But why?
• Easier to read
• Maintainability
• Extensibility
• Isolation of change
• Easier to test

4.
@gpespn
B+

5.
@gpespn
C-

6.
@gpespn
New Feature!
Guest sessions

7.
@gpespn

8.
@gpespn
F-

9.
@gpespn
I just want to
send a message
to an object

10.
@gpespn
-W
oof!
-M
eow
!

11.
@gpespn
Polymorphism
tell don't ask

12.
@gpespn

13.
@gpespn

14.
@gpespn

15.
@gpespn
still have conditional!

16.
@gpespn
Create a high
level abstract
class

17.
@gpespn

18.
@gpespn
Abstract Subclass Subclass

19.
@gpespn
Polymorphism

20.
@gpespn

21.
@gpespn
Whats the catch?
• Parallel interfaces
• Design patterns that are confusing to those unfamiliar
to them
• New words/vocabulary into application. LOC went up!
• Increased big picture complexity in exchange for
macro clarity
• Too many Objects

22.
@gpespn

23.
@gpespn
Questions?