How to include file from another file in the same directory of the same project?

Question

I started a new project in rust (it's my first project in rust, but my first programming language). I added a few functions, types and unit test in main.rs. Then I wanted to move it in two new files foo.rs and bar.rs.

How do I import/include/use bar.rs from foo.rs?

I already read:

Neither have the following structure

src/
|-- main.rs
|-- foo.rs
|-- bar.rs

Where foo.rs is trying to use the content of bar.rs.

If I try to use a type Bar declared in bar.rs directly from foo.rs, I get:

error[E0433]: failed to resolve: use of undeclared type or module `Bar`
  --> src/foo.rs

If I add mod bar at the beginning of foo.rs isn't any better:

error[E0583]: file not found for module `bar`
 --> src/foo.rs
  |
1 | mod bar;
  |     ^^^
  |
  = help: name the file either foo/bar.rs or foo/bar/mod.rs inside the directory "src"

And finally (but I wasn't expecting this one to work), with use bar; in foo.rs:

error[E0432]: unresolved import `bar`
 --> src/foo.rs
  |
1 | use bar;
  |     ^^^ no `grammar` external crate

In a mainish module (main.rs, lib.rs, or subdir/mod.rs), you need to write mod a; for all other modules that you want to use in your whole project (or in the subdir). In any other module, you need to write use a; or use a::foo; You need both mod bar; and use bar; (actually crate::bar here) — trent
– trent, Commented Dec 2, 2019 at 23:30
Oh, thanks. Why didn't you create a "real" answer so I could have selected it to flag this question as answered? — Robin
– Robin, Commented Dec 3, 2019 at 1:19
I was on mobile and didn't have the time to dedicate to a good answer. Also, I was pretty sure this had already been answered here, and I prefer to link questions together rather than write new answers. I found How to include files from same directory in a module using Cargo/Rust? and Why can't I import module from different file in same directory? (which was marked as a duplicate of one of the ones you linked, but also has an answer of its own). — trent
– trent, Commented Dec 3, 2019 at 12:29

Raleigh L. · Accepted Answer · 2023-07-11 06:32:13Z

2

I answered a very similar question here: https://stackoverflow.com/a/76659218/1576548

There's 2 different problems at hand -- there's how to import code from related modules (e.g. a helpers.rs) into your main.rs, but the procedure for doing that is different than importing code from other NON-MAIN modules into other NON-MAIN modules. The example I gave in the aforementioned question uses a.rs, b.rs, and main.rs all in the same directory, where you want to import functions between a.rs and b.rs.

answered Jul 11, 2023 at 6:32

Raleigh L.

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