Mastering Rust - Second Edition

Nested modules

The simplest way to create a module is by using the mod {} block within an existing module. Consider the following code:

// mod_within.rsmod food {    struct Cake;    struct Smoothie;    struct Pizza;}fn main() {    let eatable = Cake;}

We created an inner module named food. To create a module within an existing one, we use the mod keyword, followed by the name of the module, food, followed by a pair of braces. Within braces, we can declare any kind of item or even a nested module. Within our food module, we declared three structs: Cake, Smoothie, and Pizza. In main, we then create a Cake instance from the food module using the path syntax food::Cake. Let's compile this program:

Strange! The compiler does not see any Cake type being defined. ...