What is the "Law of Demeter"? (Don't talk to strangers)
Law of Demeter
The Law of Demeter is a guideline for minimizing knowledge between objects. A method should generally communicate with its immediate collaborators rather than navigating through long chains of unrelated objects. The common symptom is code such as order.getCustomer().getAddress().getCity().getName(). Such chains expose internal object structure and increase coupling. The principle is a heuristic rather than an absolute prohibition on method chaining.
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Prefer interactions with immediate collaborators.
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Avoid excessive knowledge of another object's internal structure.
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Long navigation chains often indicate misplaced responsibility.
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The principle reduces coupling and makes refactoring safer.
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Not every fluent API chain violates the spirit of Demeter.
Follow-up Questions
- Does every method chain violate Law of Demeter?
- How does Law of Demeter relate to encapsulation?
- How can you refactor a long navigation chain?
- What is Tell, Don't Ask?