Organizing Your Imports With a Prelude

Hands-on Rust — by Herbert Wolverson (44 / 120)

👈 Dividing Your Code Into Modules | TOC | Storing the Dungeon Map 👉

Prefixing every map access with map:: or crate::map:: is unwieldy and will get more cumbersome as you add more modules. When you access a Rust library, it’s common for the library author to have placed everything you need in a convenient prelude. You used bracket-lib’s prelude in ​Hello, Bracket Terminal​. You can simplify module access by making your own prelude to export common functionality to the rest of the program. Add the following to your main.rs file:

BasicDungeonCrawler/dungeon_crawl_map/src/main.rs

​​①​​mod​ map; 
​ 
​​②​​mod​ prelude { 
​​③​    ​pub​ ​use​ ​bracket_lib​::​prelude​::*; 
​​④​    ​pub​ ​const​ SCREEN_WIDTH: i32 = 80; 
​     ​pub​ ​const​ SCREEN_HEIGHT: i32 = 50;
​​⑤​    ​pub​ ​use​ ​crate​::​map​::*; 
​ }
​ 
​​⑥​​use​ ​prelude​::*;

​①​
Add the module to your project with mod.

​②​
The mod keyword can also be used to declare a new module in your source code. Because this is the top level of your crate, you don’t need to make it public — modules branching from crate are visible throughout your program.

​③​
Publicly using the bracket_lib prelude re-exports it inside your prelude. Anything that uses your prelude also uses bracket_lib.