The document describes the state pattern and its implementation using a gumball machine example. The state pattern allows an object to change its behavior when its internal state changes, making it appear that the object has changed its class. The document outlines defining a State interface and implementing state classes for each machine state. It also describes reworking the Gumball Machine class to delegate to the appropriate state class and removing conditional code. This implements the state pattern and allows changing the gumball machine's behavior by changing its current state object.

1. STATE
PATTERNS
Team “CODINO”:
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2. Allows an object to alter its
behavior when its internal state
changes. The object will appear to
change its class.
State Patterns
Definition

4. State diagram for Gumball
matching

6. Coding's for Gumball
matching class

9. Coding’s for Gumball
testing class

11. Output

14. What will happened if
change request?

16. New State Diagram

18. Code will be changed as…

20. The New
Design…
1. First, define a State interface that
contains a method for every action in
the Gumball Machine.
2. Then, implement a state class for every
state of machine. These classes will be
responsible for behavior of the machine
when it in the corresponding state.
3. Finally, get rid of all of our conditional
code instead delegate to the state
class to do the work for us.

21. Defining the state
interfaces and classes

23. Behavior in each class
when action is called

26. Reworking the Gumball
Machine

28. Complete Gumball
Machine class

30. Implementation of state
classes

35. Gumball 1 in 10 game

40. Output

42. Refill the Gumball Machine

44. Differences between State
and Strategy

45. • Client usually specifies the
strategy object that the context is
composed with. While the pattern
provides the flexibility to change
the strategy object at runtime,
there is typically one strategy
object that is most appropriate for
the context object.
State
• Set of behavior encapsulated in
state objects; at any time the
context is delegating to one of
those state. Over time, the current
states changes across the set of
state objects to reflect the
internal state of the context, so
the context’s behavior changes
over time. Client knows very little,
if anything, about the state
objects.
Strategy

46. • Alternative to putting lots of
conditional in your context:
you can simply change the
state object in the context to
change it’s behavior!
• Flexible alternative to sub
classing: if you use
inheritance to define the
behavior of a class, you can
stuck with it even if you
need to change it. With
strategy you can change the
behavior by composing with
different objects!