模块

说实话，教程这块看得有点晕:

  • Start from the crate root: When compiling a crate, the compiler first looks in the crate root file (usually src/lib.rs for a library crate or src/main.rs for a binary crate) for code to compile.
  • Declaring modules: In the crate root file, you can declare new modules; say, you declare a “garden” module with mod garden;. The compiler will look for the module’s code in these places:
    • Inline, within curly brackets that replace the semicolon following mod garden
    • In the file src/garden.rs
    • In the file src/garden/mod.rs
  • Declaring submodules: In any file other than the crate root, you can declare submodules. For example, you might declare mod vegetables; in src/garden.rs. The compiler will look for the submodule’s code within the directory named for the parent module in these places:
    • Inline, directly following mod vegetables, within curly brackets instead of the semicolon
    • In the file src/garden/vegetables.rs
    • In the file src/garden/vegetables/mod.rs
  • Paths to code in modules: Once a module is part of your crate, you can refer to code in that module from anywhere else in that same crate, as long as the privacy rules allow, using the path to the code. For example, an Asparagus type in the garden vegetables module would be found at crate::garden::vegetables::Asparagus.
  • Private vs public: Code within a module is private from its parent modules by default. To make a module public, declare it with pub mod instead of mod. To make items within a public module public as well, use pub before their declarations.
  • The use keyword: Within a scope, the use keyword creates shortcuts to items to reduce repetition of long paths. In any scope that can refer to crate::garden::vegetables::Asparagus, you can create a shortcut with use crate::garden::vegetables::Asparagus; and from then on you only need to write Asparagus to make use of that type in the scope.

几个重点:

  • mod XXXXX;用于声明引用了一个模块。rust会从指定的文件去找。
  • 模块默认对外层都是不可见的。需要使用pub来使模块和其中的函数可见。
  • 使用use XXXXX::YYYYY:ZZZZZ后，在本模块中可以直接使用ZZZZZ来简化调用。

集合: Hash map

    use std::collections::HashMap;

    let mut scores = HashMap::new();

    scores.insert(String::from("Blue"), 10);
    scores.insert(String::from("Blue"), 25);

    println!("{:?}", scores);