[Refactoring to Patterns] 6.2 Move Creation Knowledge to Factory

1. 6.2.
Move Creation Knowledge to Factory
6. Creation (6.2)
YAO, LI-WEI
2014/12/04
Qlync Inc., RD Reading
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2. ⽤用以具現(Instantiate)
class的各種資料和程式碼
蔓延(sprawl)於許多classes
將創建知識(Creation Knowledges)搬
移至單個Factory class中
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3. Creation Sprawl
(Solution Sprawl)
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4. What is Factory?
Simple Factory
Factory Method
Abstract Factory
http://corey.quickshiftconsulting.com/blog/first-post
http://blog.csdn.net/dragonwuboy/article/details/16839509
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5. Simple Factory
Creation logic in factory, hard to add new product
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6. Factory Method
Interfaced factory method, OCP (Open Closed Principle), client decide product
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7. Abstract Factory
Create a family of related objects, use factory method
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8. ⽤用以具現(Instantiate)
class的各種資料和程式
碼蔓延於許多classes
將創建知識(Creation Knowledges)搬
移至單個Factory class中
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9. Pros ana Cons
(+) 可以統合創建邏輯(creation logic)和具現/組
態偏好(instantiation/configuration preferences)。︒
(+) 將客⼾戶端和創建邏輯(creation logic)解除耦合
(decouple)。︒
(-) 此法比直接具現(direct instantiation; 亦即直接
創建)更令設計複雜⼀一些。︒
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10. Mechanics
1. 令instantiator經由Creation Method具現product
2. 建⽴立即將成為Factory的新class
3. 將Creation Method移至Factory, 設為nonstatic
4. 令instantiator改⽽而具現Factory, 呼叫Factory取得class實體
5. 將具現任務中所需的資料及函式盡可能移至Factory
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11. Example…
and
Discussion…
http://www.informit.com/articles/article.aspx?p=1398606&seqNum=2
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