Modules are the building blocks of V programs. They allow you to split your code into separate files and organize it into logical units. Modules can be imported and reused in other modules.

A module is a folder that contains at least one file with a V source code. Module names should be kept short, no more than 10 characters, and use snake_case. As in Go, circular imports are not allowed. All modules are compiled statically into a single executable file.

Create new modules

To create a new module, create a folder with the name of the module and place the V source files in it.

cd your-project
mkdir mymodule

Then add the file mymodule/myfile.v:

module mymodule pub fn say_hi() { println('Hi from mymodule!') }

Each file in a module must have the module keyword with the name of the module at the beginning of the file. The folder cannot contain files that define another module.

Now you can use the module in your code:


import mymodule fn main() { mymodule.say_hi() }

To learn more about importing modules, see the import documentation.

Nested modules

Sometimes it is useful to combine several modules into one.

To do this, just create another folder inside the folder of the existing module with the name of the submodule:

mkdir mymodule/submodule

Then create a file mymodule/submodule/myfile.v:

module submodule pub fn say_hello() { println('Hello from mymodule.submodule!') }

Now, to use a submodule, you need to specify the full path to it, separating the names with a dot:

import mymodule.submodule fn main() { submodule.say_hello() }

Symbol visibility

In the examples above, we used the pub keyword when declaring the functions. By default, all functions, structures, constants, and types are private (not exported). To make them available to other modules, add pub before their declaration. This allows other modules to use them in their own code.

The following function can only be used inside the mymodule module:

fn private_function() { }

And this function can be used in any other module:

pub fn public_function() { }

init functions

If you want a module to automatically call some setup/initialization code when it is imported, you can use a module init function:

fn init() { // your setup code here ... }

The init function cannot be public – it will be called automatically. This feature is particularly useful for initializing a C library.