principles:high_cohesion
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The cohesion of a module is a measure for how well the internal parts of a module (e.g. the methods and attributes of a class) belong together. Having a high cohesion means, that a module should only comprise responsibilities which belong together. | The cohesion of a module is a measure for how well the internal parts of a module (e.g. the methods and attributes of a class) belong together. Having a high cohesion means, that a module should only comprise responsibilities which belong together. | ||
- | Several kinds of cohesion can be distinguished some of which are strong and some of which are loose. So strong forms of coupling should be preferred. | + | Several kinds of cohesion can be distinguished some of which are strong and some of which are loose. So strong forms of coupling should be preferred: FIXME add explanation of cohesion types |
===== Rationale ===== | ===== Rationale ===== | ||
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+ | ===== Strategies ===== | ||
+ | * Divide one large module into several smaller but more cohesive ones | ||
===== Caveats ===== | ===== Caveats ===== | ||
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===== Origin ===== | ===== Origin ===== | ||
- | W. P. Stevens, G. van Niekerk, G. J. Myers, L. L. Constantine: | ||
===== Evidence ===== | ===== Evidence ===== | ||
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/ | / | ||
- | * [[wiki: | + | * [[wiki: |
- | * [[wiki: | + | * [[wiki: |
/ | / | ||
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- | ==== Class level cohesion ==== | ||
- | |||
- | Robert Cecil Martin (Uncle Bob) describes maximal cohesion at class level as "a class in which each variable is used by each method" | ||
- | |||
- | "In general the more variables a method manipulates the more cohesive that method is to its class." | ||
- | (Clean Code: A Handbook of Agile Software Craftsmanship - Chapter 10) | ||
===== Further Reading ===== | ===== Further Reading ===== | ||
- | * Albert Endres and Dieter Rombach: //[[resources: | + | * Albert Endres and Dieter Rombach: //A Handbook of Software and Systems Engineering// |
* [[wp> | * [[wp> | ||
* [[wiki> | * [[wiki> | ||
- | * {{page> | + | * Craig Larman: //Applying UML and Patterns |
===== Discussion ===== | ===== Discussion ===== | ||
Discuss this wiki article and the principle on the corresponding [[talk: | Discuss this wiki article and the principle on the corresponding [[talk: |
principles/high_cohesion.txt · Last modified: 2021-10-18 21:36 by christian