Public "getter method" vs pub field

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The pub field allows a few more things that you may or may not want:

  • Construction: users can create a Stroke { duration: 42 }.
    • This also means it's a breaking change for you to add or remove any fields.
    • You can add a private field to avoid this, even just a dummy _private: () that takes no space.
  • Mutation: if the user has some mut var: Stroke or &mut Stroke, they can change the duration. This might be convenient, but you need to be careful if there are any invariants to uphold on that field.
  • Partial borrow: if a user binds let var = &stroke.duration; they can still use other fields of the Stroke without any complaint from the borrow checker.
    • This especially applies with mutation, since that's an exclusive borrow. With your getter, borrowing duration will lock the whole struct since it goes through the full &self. The user could still do other immutable accesses, but not anything that wants mutable access to any part of the struct.
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