Design Pattern Series
State Method
By: Chip Salim
TBD 2017
#2
Agenda
- Recollection from DP Session #1
- The State Pattern
Recollection
- Session Series as re-freshers & discovery
- Beginner, Mid-Level, and Advanced
- Shared vocabs. to increase comm.
Recollection
- Basics of Design Pattern
- What it is and is not
Recollection
- Start with a KISS and A PIE
- Refactoring
- Apply OOP
Recollection
Types
- Creational, Behavioral, Structural, Concurrency
Recollection
Strategy Pattern
Defines a family of algorithms, encapsulates each one, and makes them interchangeable. Strategy lets the algorithm vary independently from clients that use it.
State Pattern
Allows an object to alter its behavior when its internal state changes. The object will appear to change its class.
Relationships
Strategy Pattern
State Pattern
Relationships
Strategy Pattern
State Pattern
- Flexible alternative to subclassing
- The client usually specifies the strategy object to compose the Context
- Policy Pattern
- A substitute to many if-then-else statements
- The client interacts with the Context. The Context delegates its internal state through its subclasses
Context
Off
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Display Main Screen
Display Login Screen
Password
Required
?
No
Yes
Password
Valid
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No
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Yes
Context
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Locked
Unlocked
Locked
Out
Display Main Screen
Display Login Screen
Password
Required
?
No
Yes
Password
Valid
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No
3rd
Attempt
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Yes
No
Switch
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Yes
Summary
The State pattern allows an object to alter its internal state (behavior) via delegation at run-time
Characterized by a long list of conditional statements
The State and Strategy patterns share the same structure, the difference is in the intent.
Result in more numbers of classes in your design
Danke!
Next Topic by Scott Carroll
Design Pattern - State Pattern
By ilusi
