oop,rust,traits , Is it possible to access struct fields from within a trait?


Is it possible to access struct fields from within a trait?

Question:

Tag: oop,rust,traits

I know object oriented programming from C# and I'm playing around with Rust right now, obviously trying to adapt the OOP-functionalities I already know from C#. There is one thing I'm really wondering about: Traits are used to group some functions to be implemented from a struct. How is it / Is it possible to access struct fields from within the trait? I could imagine declaring fields inside the trait, so the fields are abstracted as well. Since I haven't found such a syntax, I'm wondering if there is any other solution? Otherwise it wouldn't be possible to have non-static methods using a trait, would it?


Answer:

This sounds like you're misunderstanding how traits work. Traits can't have fields. If you want to provide access to a field from a trait, you need to define a method in that trait (like, say, get_blah).

If you're asking whether you can access fields of a struct from within that struct's implementation of a trait, then yes. The struct knows it's own type, so there's no problem.

trait Pet {
  fn is_smelly(&self) -> bool;
}

struct Dog {
    washed_recently: bool,
}

impl Pet for Dog {
  fn is_smelly(&self) -> bool {
    !self.washed_recently
  }
}

Edit: another thing I just thought of. If you're writing a default implementation of a trait (i.e. defining a method body within the trait), then no, you can't access fields. A default implementation can only use methods that are defined on the trait, or in a super trait.


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