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The Visitor pattern is a Gang of Four staple that separates traversal from processing. Pony's structural typing makes it lighter than the traditional double-dispatch version, but the core idea is just as useful. Uses a simplified document renderer as the running example, with ponylang/templates referenced as a real-world exemplar in the discussion.
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Rename sinks to visitors. |
jemc
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Mar 25, 2026
| Pull the "what to do with each segment" part out into an interface. The walker calls the interface; different implementations decide what happens with each piece. | ||
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| ```pony | ||
| interface ref DocumentSink |
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Suggestion to replace Sink term with Visitor (throughout the pattern text)
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also comment on the closed world nature of and how that plays into this solution. |
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The Visitor pattern is a Gang of Four staple that separates traversal from processing. Pony's structural typing makes it lighter than the traditional double-dispatch version, but the core idea is just as useful.
Uses a simplified document renderer as the running example, with ponylang/templates referenced as a real-world exemplar in the discussion. Also broadens the Behavioral Patterns category description and adds a cross-reference from the Notifier pattern page.