Exposing a different structure with `pub use`

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1

In section 7.4, The Book states:

With pub use, we can write our code with one structure but expose a different structure.

Could someone provide an example of using pub use to create an alternate structure? I'm having trouble understanding what exactly it's talking about without one. Thanks!

2

By structure here, they're talking about the hierarchy of modules (not a struct). Let me contrive a different example, maybe I have a

pub mod shapes {
    mod ovoids { /* circles, spheres, ... */ }
    mod sharps { /* squares, cubes, tesseracts, ... */ }
   // ...

But my typical consumers deal with specific sets of dimensions, so I export

    pub mod two_d {
        pub use crate::ovoids::circle;
        pub use crate::sharps::square;
    }
    pub mod three_d {
        pub use crate::ovoids::sphere;
        pub use crate::sharps::cube;
    }
    // ...
}

Then when developing, I see a "structure" organized by sharpness or whatever (in the private modules / where the code actually lives), while consumers of my crate see a structure organized by the number of dimensions (the public re-exports).

7 Likes
3

Fantastic example. Thank you so much for taking the time to reply!

So, if I'm understanding correctly, consumers of the two_d module would use circle as two_d::circle instead of ovoids::circle. Is that correct?

4

Correct -- and in this example (and the one in the book), consumers don't get a choice. The re-exports are the only paths visible, because they're re-exporting from non-pub paths. mod ovoids is private so they can't name ovoids::circle directly.

5

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