///模块

pub fn modules() {

struct_visibility();

cfg();

}

fn struct_visibility() {

mod my {

//公有结构体和公有字段

pub struct OpenBox<T> {

pub contents: T,

}

//公有结构体和私有字段

#[allow(dead_code)] //禁用编译器的 未使用警告

pub struct ClosedBox<T> {

contents: T,

}

impl<T> ClosedBox<T> {

//公有的构造函数

pub fn new(contents: T) -> ClosedBox<T> {

ClosedBox { contents: contents }

}

}

}

let open_box = my::OpenBox {

contents: "public information",

};

println!("The open box contains: {}", open_box.contents);

//ERROR

//let closed_box = my::ClosedBox { contents: "classified information" };

//使用构造函数可以

let _closed_box = my::ClosedBox::new("classified information");

//ERROR

//println!("The closed box contains: {}", _closed_box.contents);

}

fn use_declaration() {

//指定别名

// use deeply::nested::function as other_function;

// other_function();

//相对路径，父级和当前级

//super 和 self

}

//extern crate rary; 导入library库

fn cfg() {

// This function only gets compiled if the target OS is linux

#[cfg(target_os = "linux")]

fn are_you_on_linux() {

println!("You are running linux!");

}

// And this function only gets compiled if the target OS is *not* linux

#[cfg(not(target_os = "linux"))]

fn are_you_on_linux2() {

println!("You are *not* running linux!");

}

println!("Are you sure?");

if cfg!(target_os = "linux") {

//target_os由rustc隐式提供，但是自定义条件条件必须使用--cfg标志传递给rustc

println!("Yes. It's definitely linux!");

} else {

println!("Yes. It's definitely *not* linux!");

}

}