rust - How do I import from a sibling module? - Stack Overflow 2. Even though I spent lots of time trying to get this to compile, I haven't been successful so far.. mod tu2 in mod.rs seems to work, but it is so ugly, that I am quite sure that it is not the solution. This syntax should not be necessary anymore. Migration. // another-file.rs pub fn method() { } // lib.rs use another_file; // <-- ERROR can not find another_file.rs another_file::method(); mcarton You will have to explicitly declare . Learning Rust Docs. ("Woof, Woof!");}} fn main {cat:: meow ();} Obviously using separate modules for this is overkill but it demonstrates the way modules work. Each module can refer to any other module in the tree much like you can use the filesystem: absolute paths begin with crate (which is like / ), and relative paths begin with self (.) When the module does not have a path attribute, the path to the file mirrors the logical module path. You don't need the mod hello in your hello.rs file. That would import all macros from util. use super::random_file_0; #[test] fn do_something_else() { assert! Modules - The Rust Reference On several occasions I tried to learn rust but failed at the apparently overcomplicated module-system. So in the . Borrowing is about taking control over a variable for a while and then returning that ownership of the variable back. How to access a main.rs static variable from a module? : rust I fixed that using a match. Modules a and b are at the same level. (random_file_0::do_something()); } or an alternative random . Even though I spent lots of time trying to get this to compile, I haven't been successful so far.. mod tu2 in mod.rs seems to work, but it is so ugly, that I am quite sure that it is not the solution. Every file is a module and cannot import another without creating a new nested module. Photo by Ahmad Qime on Unsplash. It's easy. On several occasions I tried to learn rust but failed at the apparently overcomplicated module-system. Define a public struct for all fields in the struct. Although borrowing allows you to have multiple references to a variable, only one reference can be mutable at any given time. Larger programs will take a fair amount . or super ( ..) The module crate::service::device::device can reach the module crate::service::device::watch by using either the long form use crate::service . 01. If we do that, Rust will expect to find either a english.rs file, or a english/mod.rs file with the contents of our module. Modules form a hierarchical structure, much like another structure in computing that you're used to: filesystems! 03. sibling - rust use struct from another file . Using a semicolon after mod front_of_house rather than using a block tells Rust to load the contents of the module from another file with the same name as the module. This can seem cumbersome at first, but you will come to understand the reasons why it works this way. To include the code from hello.rs in your main.rs, use mod hello;. The above example can alternately be expressed with crate::util's contents in a file named util/mod.rs.It is not allowed to have both util.rs and util/mod.rs.. To continue with our example and extract the hosting module to its own file as well, we change src/front_of_house.rs to contain only the declaration of the hosting module: . What you see on your filesystem you also find . b. Now I'm trying to split the main module in two . Since main is the parent of mod_x, you can access the mod_y from mod_x with super::mod_y or crate::mod_y. Before Rust 2018, you had to import macro from other crates by adding the attribute #[macro_use] to the extern crate util; statement. Rust 2018 To import a module on the same level, do the following: random_file_0.rs // Note how this is a public function. For this example, let's start with the code in Listing 7-3: Filename: src/lib.rs How to "use another-file" in rust? Using these two techniques, we can break up our crate into two directories and seven files: $ tree . Understand that if the module is not public you won't be able to access it within your file. My example has three files inside the src folder. Modules should be prefixed with pub keyword to make it public. By using pub use, you can export a macro from a module of your crate (in addition to it being exported at the root). Note that we need to use . The next thing that confuses people is that you would assume we declare a file as module in the same file. report. level 1. Another special case is pub use. I have created various other Rust command-line tools since then, but I love coming back to fd, as I personally use it the most.. A lot has changed since I started learning Rust by working on fd.The project has matured and grown a lot. Modules. The module system is pretty central and thus important to learning Rust. and it compiles without errors. How do i use hyphens instead (another-file.rs)? For this, create a another Cargo binary project with cargo new --bin test-serde-json, go into the test-serde-json directory and edit Cargo.toml. However, there are good reasons for this, as we'll see later. Define modules in module index file. Amin Published at Dev. The file matrix.rs 1 in the directory math is just the module math::matrix. English. A module without a body is loaded from an external file. If we only define pub struct, and not for the field, the field will be automatically be private. 1 min read. The main program and its module files will be recompiled each time. By using pub use, you can export a macro from a module of your crate (in addition to it being exported at the root). a. 75% Upvoted. I also forgot to put an & before the String::from("AABC") thing, and had a type mismatch between the from_string (which returned a Result) and the Grid type.. Your crates can depend on other libraries from crates.io or other registries, git repositories, or subdirectories on your local file system. Each module can refer to any other module in the tree much like you can use the filesystem: absolute paths begin with crate (which is like / ), and relative paths begin with self (.) You need to create a tree of We could then access MyNamespace.MyClass.MyFunction () if we had access to it. To continue with our example and extract the hosting module to its own file as well, we change src/front_of_house.rs to contain only the declaration of the hosting module: "Including" external code To read a good introduction into modules, please read the chapter on modules in the Rust book. src/main.rs. Using a semicolon after mod front_of_house rather than using a block tells Rust to load the contents of the module from another file with the same name as the module. fn main() { greetings::hello(); } mod greetings { // ⭐️ By default, everything inside a module is private pub fn hello() { // ⭐️ So function has to be public to access from outside println! Either with crate or super. The file mod.rs is just the directory's module. You probably don't want to use the . It has to be in order to be // usable from other files (in this case `random_file_1.rs`) pub fn do_something() -> bool { true } random_file_1.rs. Re-exporting. Ancestor module path components are directories, and the module's contents are in a file with the name of the module plus the .rs extension. ("Hello, world!");}} which I run using cargo build && cargo run. Therefore you can't just reference them directly with a simple import or drilled namespacing a la JavaScript or C# and use them right away. Modules can be public or private. Edit it like so . So after that, they can be accessed . ("Hello, world!"); } } Modules can also be nested. There's no such thing as a "file" when you reference your resource. Another Rust feature related to ownership is borrowing. There's a lot of Rust documentation about using modules, but I haven't found an example of a Cargo binary that has multiple modules, with one module using another. blocks, using a src/my_module.rs file, or using a src/my_module/mod.rs file, but the choice of approach is immaterial to the namespace structure being constructed. fd is my very first Rust project. fn main() { greetings::hello(); } mod greetings { // ⭐️ By default, everything inside a module is private pub fn hello() { // ⭐️ So function has to be public to access from outside println! To use a mod that exists inside the file, you can just type its name as namespace and drill down to the resource you're looking for. best . Functions within a public module must also be made public. or super ( ..) The module crate::service::device::device can reach the module crate::service::device::watch by using either the long form use crate::service . We can use Rust's module system along with multiple files to split up Rust projects so not everything lives in src/lib.rs or src/main.rs. However, if these functions are static functions then you don't need a struct at all, you can simply export bare functions from your module: mod A . In fact, if you go back in (Git) history, the project was originally written in C++. This thread is archived. English. Note: Prior to rustc 1.30, using mod.rs files was the way to load a module with nested children. Add pub mod mod1; pub mod mod2; in src/lib.rs / src/main.rs / src/foo/mod.rs. Instead of continuing to talk theoretically about ownership and borrowing, let's look at a code . The files are then "included" via the module system. As @giuliano-oliveira's answer recommends. You can also temporarily override the location of a dependency — for example, to be able to test out a bug fix in the dependency that you are working on locally. This can be a powerful way of growing a project: a module might start life as one or two types and functions inside a . How do i use hyphens instead (another-file.rs)? Before Rust 2018, you had to import macro from other crates by adding the attribute #[macro_use] to the extern crate util; statement. Like every tree, the module tree has a root. Luckily, Python is an extendable language, and that can be done easily enough. a better solution is serde_json where you serialize Rust data structures into JSON and deserialize JSON into Rust. If your only concern is speed, you could use Cython or the library called Numba that would . However, in rust, if I have a: file_x.rs file_y.rs How can I tell file_x.rs to run a function in file_y.rs? Related code and data are grouped into a module and stored in the same file. 3 years ago. A directory is just a module path component. You can use a whole bunch of Rust keywords to navigate between the modules of your crate: super::components::Header // `super` is like a `parent` of your current mod crate::components::Header // `crate` is like a root of you current crate And to include submodules of current mod: self::submodule1::MyStruct // `self` is like current module --- Original question ----My structure looks something . Rust tries really hard to make things easy (because it feels guilty for all the suffering with burrows and lifetimes) so to make a crate a . We need to explicitly build the module tree in Rust, there's no implicit mapping to file system To add a file to the module tree, we need to declare that file as a submodule using the modkeyword. Worked perfectly. Components in a private module cannot be accessed by other modules. 10. amin Using another_file with underscore in as word separators works fine in Rust. fn main . Hi guys. This syntax should not be necessary anymore. Rust doesn't see files as files, but it sees them as modules and files inside folders as sub-modules. Note that in these files, you don't need to re-declare the module: that's already been done with the initial mod declaration. This isn't possible. Code in any file but the crate root (main.rs for executables, lib.rs for libraries) is automatically namespaced in a module. share. To include the code from hello.rs in your main.rs, use mod hello;. Use #[path] main.rs #[path = "./mod2.rs"] mod mod2; fn run() { mod2::mod2fn() } Why? You could also check out Rust by Example on that topic. This is a common pitfall for new Rust devs and . The Rust module rules are: A source file is just its own module (except the special files main.rs, lib.rs and mod.rs). fn main . Modules in Rust are private by default. Module filenames may also be the name of the module as a directory with the contents in a file named mod.rs within that directory. 01. The crate::mod_y syntax has an older form, which looks like ::mod_y. Code in any file but the crate root (main.rs for executables, lib.rs for libraries) is automatically namespaced in a module.To include the code from hello.rs in your main.rs, use mod hello;.It gets expanded to the code that is in hello.rs (exactly as you had before). Sort by. Module with hyphens in it. It gets expanded to the code that is in hello.rs (exactly as you had before). If you'd like to include the To import a module on the same level, do the following: random_file_0.rs // Note how this is a public function. Rust automagically looks for it inside the file, if doesn't find it, looks for a file with the module name in the same folder (in this case . Amin Published at Dev. Rust 2018. (2) By following this guide I created a Cargo project. New comments cannot be posted and votes cannot be cast. Then, within the tests mod, I put "use super::cell" as the first line. Basically, in C# if we want to access another namespace we would put using MyNamespace; at the top of the file. First we need to tell Rust where each file belongs in the module hierarchy, and then we can import our module using the "module path" rather than the filesystem path. In the same file. main.rs: It has to be in order to be // usable from other files (in this case `random_file_1.rs`) pub fn do_something () -> bool { true } random_file_1.rs In another file. Code in any file but the crate root (main.rs for executables, lib.rs for libraries) is automatically namespaced in a module. use module::A::foo; Not a module `A` 3 comments. use statements import only what we've specified into the scope, instead of importing all elements of a module or crate. When creating a module, you can export things from another module into your module. Now it works. In C/C++, you can call a function implemented in another file very easily, just declare it, and insert the implementation file into the project, and you are done. Check Rust's visibility and privacy reference for more information. It didn't matter which file we called that in. Modules. On the contrary, functions in a public module can be accessed by other modules. I just found out that the linking model of rust is very different from that of C/C++.