Modules

One line: How a program larger than one file is organised — the namespace, the wall, the shortcut, and the two item kinds that live at the top of a module rather than inside a function.

A module does two jobs at once, and confusing them is where most of the difficulty comes from. It is a namespace, so two types can both be called Result. And it is a privacy boundary, so an invariant can be enforced by making the field private — with the catch that the boundary is the module, not the type, so everything in the same mod is on the inside.

Lesson	Level	What it covers
Modules and visibility	201	Private by default, the four pub forms, and the door a helper in the same module leaves open
Bringing names in with use	101 → 201	A shortcut, not an import — plus the rename that fixes a collision and the glob that causes one
One module per file	201	mod name; is a declaration; the tree is the same either way; and the file nobody declared
const and static	201	Substituted at every use, versus one address for the program — and const fn
What an attribute is	201	derive, the four lint levels, cfg, and the field order a derived Ord reads

The order to read them

The first three are one story told from three sides: what a module is, how to refer into one, and where the files go. The last two are items that live at module level and have nowhere else to be taught — const and static because they are the first things you put next to a mod, and attributes because #[derive] is on almost every type in this library and nothing else defines it.

What is next door

Testing is the other thing #[cfg(test)] is for, and it has a section of its own. The invariant that private fields protect is the newtype. And the use line whose absence produces the strangest error in Rust — a method that exists but cannot be found — is a trait must be in scope.

Cargo, crates and dependencies are toolchain rather than language, and live in Tooling.

Po polsku

Moduł (module) robi w Ruscie dwie rzeczy naraz i stąd bierze się większość trudności: jest przestrzenią nazw — dzięki czemu dwa różne typy mogą nazywać się Result — a przy okazji granicą prywatności. Ta druga rola zaskakuje osoby przychodzące z Javy czy C#, gdzie „prywatne” znaczy prywatne dla klasy: w Ruscie ścianę stawia moduł, a nie typ, więc każda funkcja leżąca w tym samym mod siedzi po wewnętrznej stronie i widzi prywatne pola cudzych struktur. Przy szukaniu materiałów warto pamiętać, że polski przekład Tour of Rust urywa się na rozdziale 5, a moduły są w rozdziale 9 — po polsku zostają pojedyncze wpisy blogowe, więc na konkretne pytanie i tak szybciej odpowie fraza angielska.

Szukaj po polsku: moduły w Ruscie · widoczność i prywatność w Ruscie · rust module system · rust pub(crate) visibility