反覆器模式與合成模式

1. Developer
Exchange
Group
深入淺出設計模式#6:
反覆器模式與合成模式
Prepare
by
Sean
Hsieh

2. Agenda
• Iterator
pa@ern
• Composite
pa@ern

3. Iterator
pa@ern

4. Scene
• Different
kind
of
container:
List,
Array
– We
have
to
enumerate
items
in
different
containers

5. We
hire(create)
a
waitress
• First
we
use
waitress
to
enumerate
items

6. What’s
wrong?
• 1.
We
code
to
the
concrete
implementaKon,
not
to
an
interface.
• 2.New
type
of
menu.
• 3.Violates
encapsula;on.
• 4.If
we
added
a
third
menu,
we
would
have
another
loop

7. Class
diagram
(so
far)
waitress
pancakehouse
menu
dinnermenu

8. Encapsula;on:
Iterator
pa?ern

9. Encapsula;on:
Iterator
pa?ern

10. Encapsula;on:
Iterator
pa?ern

11. Class
diagram
(aTer
modify)
waitress
pancakehousemenu
dinnermenu

12. ATer
modify,
we
know..
• 1.The
menu
implement
are
now
encapsulated
• 2.The
loop
that
polymorphically
handles
any
collecKon
of
items.
• 3.The
waitress
now
uses
an
interface.

13. Final
step:
Let
menu
interfaces
exactly
the
same

14. Design
Principle:
Single
Responsibility
• 1.
A
class
should
have
only
one
reason
to
change.
• 2.Having
two
ways
to
change
increases
the
probability
the
class
will
change
in
the
future,
and
when
it
does,
it’s
going
to
affect
two
aspects
of
your
design.

15. Composite
pa@ern

16. If
we
need
sub
menu…
• The
framework
now
we
use
can
not
handle
that.

17. Apply
composite
pa@ern
before
coding
• The
composite
pa@ern
allow
you
to
composite
objects
into
tree
structures
to
represent
part-­‐whole
hierarchies.

18. Class
diagram

19. MenuComponent
(super
class)

20. MenuItem
(sub
class)

21. Menu
(sub
class)

22. Recursive
visit

23. ATer
modify,
we
know..
• 1.The
menu
implement
are
now
encapsulated
• 2.The
loop
that
polymorphically
handles
any
collecKon
of
items.
• 3.The
waitress
now
uses
an
interface.

24. More

25. Image
editor

26. FuncKons
of
image
editor

27. Class
diagram
of
image
editor

28. Wallpaper
Product

29. Class
diagram
of
Wallpaper
Product