By default, the items in a module have private visibility, but this can be
overridden with the pub modifier. Only the public items of a module can be
accessed from outside the module scope.
// A module named `my`
mod my {
// Items in modules default to private visibility.
fn private_function() {
println!("called `my::private_function()`");
}
// Use the `pub` modifier to override default visibility.
pub fn function() {
println!("called `my::function()`");
}
// Items can access other items in the same module,
// even when private.
pub fn indirect_access() {
print!("called `my::indirect_access()`, that\n> ");
private_function();
}
// Modules can also be nested
pub mod nested {
pub fn function() {
println!("called `my::nested::function()`");
}
#[allow(dead_code)]
fn private_function() {
println!("called `my::nested::private_function()`");
}
}
// Nested modules follow the same rules for visibility
mod private_nested {
#[allow(dead_code)]
pub fn function() {
println!("called `my::private_nested::function()`");
}
}
}
fn function() {
println!("called `function()`");
}
fn main() {
// Modules allow disambiguation between items that have the same name.
function();
my::function();
// Public items, including those inside nested modules, can be
// accessed from outside the parent module.
my::indirect_access();
my::nested::function();
// Private items of a module cannot be directly accessed, even if
// nested in a public module:
// Error! `private_function` is private
//my::private_function();
// TODO ^ Try uncommenting this line
// Error! `private_function` is private
//my::nested::private_function();
// TODO ^ Try uncommenting this line
// Error! `private_nested` is a private module
//my::private_nested::function();
// TODO ^ Try uncommenting this line
}