The visitor design pattern
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The Visitor Design Pattern allows defining a new operation over elements in an object structure without changing the classes of the elements. It puts the operations in visitor classes so new operations are easy to add. While this keeps behavior partitioned and localized, adding new element classes is difficult as it requires changes to the visitor interface and implementations. The element interface may also need powerful operations that compromise encapsulation.
The visitor design pattern
- 1. The Visitor Design PatternSamnangChhunYoolk Inc.
- 2. Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.What this?Open Closed Principle is the keyThe Visitor Design Pattern
- 3. Structure
- 4. Example
- 5. ConsequencesBenefitsAdding new operations is easyRelated behavior isn’t spread over the classes defining the object structure; it’s localized in a visitor. Unrelated sets of behavior are partitioned in own visitor subclasses.LiabilitiesAdding new ConcreteElement class is hard. Each new ConcreteElement give rise to a new abstract operation on Visitor and a corresponding implementation in every ConcreteVisitor class.The ConcreteElement interface must be powerful enough to let visitors do their job. You may be forced to provide public operations that access an element’s internal state, which may compromise its encapsulation.
- 6. Don’t forget to review all of them again and again
- 7. Thank you!