29 lines
1.2 KiB
Markdown
29 lines
1.2 KiB
Markdown
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---
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layout: pattern
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title: Acyclic Visitor
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folder: acyclic-visitor
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permalink: /patterns/acyclic-visitor/
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categories: Behavioral
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tags:
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- Java
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- Difficulty-Intermediate
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---
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## Intent
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Allow new functions to be added to existing class hierarchies without affecting those hierarchies, and without creating the troublesome dependency cycles that are inherent to the GOF VISITOR Pattern.
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## Applicability
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This pattern can be used:
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* When you need to add a new function to an existing hierarchy without the need to alter or affect that hierarchy.
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* When there are functions that operate upon a hierarchy, but which do not belong in the hierarchy itself. e.g. the ConfigureForDOS / ConfigureForUnix / ConfigureForX issue.
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* When you need to perform very different operations on an object depending upon its type.
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* When the visited class hierarchy will be frequently extended with new derivatives of the Element class.
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* When the recompilation, relinking, retesting or redistribution of the derivatives of Element is very expensive.
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## Related patterns
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* [Visitor Pattern](../visitor/README.md)
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## Credits
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* [Acyclic Visitor](http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf)
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