In 1992, Jack Reeves wrote a seminal article in the C++ Journal entitled “What is Software Design?” In this article, Reeves argues that the design of a software system is documented primarily by its source code. 源碼就是設計。UML diagrams 也許能夠展示一部分設計，但它不是設計的全部。只有源碼才是設計。非常推薦這篇文章！！！

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Design Smells – The Odors of Rotting Software

• ? Rigidity – The system is hard to change because every change forces many other changes to other parts of the system. 僵化=難于修改
• ? Fragility – Changes cause the system to break in places that have no conceptual relationship to the part that was changed. 脆弱=一改就亂
• ? Immobility – It’s hard to disentangle the system into components that can be reused in other system. 難以提取獨立出來
• ? Viscosity – Doing things right is harder than doing things wrong. 粘滯=做好事難。比如編譯時間太長，開發人員就會傾向于修改只需要部分編譯的代碼，即使這樣修改與設計沖突。
• ? Needless Complexity – The design contains infrastructure that adds no direct benefit. 沒必要的復雜=過度設計。我們應該保持設計的flexible，而不是一開始就認為后續會有很多變化，從而把架構寫的很復雜。如何保持？看后面介紹的原則，以及測試驅動會驅動你的。
• ? Needless Repetition – The design contains repeating structures that could be unified under a single abstraction. 重復=濫用粘貼
• ? Opacity-It’s hard to read and understand. it does not express its intent well.晦澀=代碼難懂

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What Stimulates the Software to Rot?

主要原因來至需求變化，而且經常要求快速實現需求，導致開發人員寫出各種違反原設計的代碼，慢慢的Smell就產生了。

然而，我們不能責怪需求的變化。If our designs are failing due the constant rain of changing requirements, it is our designs and practices that are at fault. We must somehow find a way to make our designs resilient to such changes and employ practices that protect them from rotting.

轉載于:https://www.cnblogs.com/ustbdavid/p/3415226.html

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