RUST-the book 7、8章
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[TOC]
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source
https://doc.rust-lang.org/book/ch07-00-managing-growing-projects-with-packages-crates-and-modules.html
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# chapter 7
### 模組管理
大型專案的RUST如何管理library、檔案結構？
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### 本章重點
* Packages:
A Cargo feature that lets you build, test, share crates
* Crates:
A tree of modules that produces a library or executable
* Modules and use:
Let you control the organization, scope, and privacy
* Paths:
A way of naming an item
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# 7.1 crate
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### crate
> A crate is the smallest amount of code that the Rust compiler considers at a time
##### 執行單一rust script時，compile 考慮該檔案是個crate
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### crate有2種
1. binary crate
programs you can compile to an executable that you can run
e.g. command-line program、server
src
/main.py
2. library crate
they don’t compile to an executable.
Instead, they define functionality intended to be
shared with multiple projects
e.g. rand crate provide the functionality
that generate random numbers
src
/lib.rs
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## 實作時間
```rust
cargo new my-project
```
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# 7.2 module
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## modules
namely paths that allow you to name items;
1. the use keyword that brings a path into scope;
2. the pub keyword to make items public
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## how module work(1)?
1. 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.
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## how module work(2)?
2. 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
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## how module work(3)?
3. 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
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## how module work(4)?
4. 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
e.g.
crate::garden::vegetables::Asparagus.
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## how module work(5)?
5. Private vs public:
6Code within a module is private from its parent modules by default. To make a module public, declare it with pub mod instead of mod.
mod dateTool<- 預設是private
pub mod dateTool <- 使mod變public
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## how module work(6)?
6. The use keyword:
Within a scope, the use keyword creates shortcuts to items to reduce repetition of long paths.
原： crate::garden::vegetables::Asparagus
使用use: use crate::garden::vegetables::Asparagus
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## 實作時間
```rust
use crate::garden::vegetables::Asparagus;
pub mod garden;
fn main() {
let plant = Asparagus {};
println!("I'm growing {:?}!", plant);
}
```
---
# 7.3 paths
----
```rust
// Absolute path
crate::front_of_house::hosting::add_to_waitlist();
// Relative path
front_of_house::hosting::add_to_waitlist();
```
:::info
記得要export給別人用的要設pub
:::
----
:::success best practice
best practice
##### package can contain both src/main.rs and src/lib.rs
1. module.tree 放 lib.rs
2. binary crate(main/rs)成為lib的user(pub物件的user)
:::
----
## 實作時間
```rust
// super
fn deliver_order() {}
mod back_of_house {
fn fix_incorrect_order() {
cook_order();
// similar to ..
super::deliver_order();
}
fn cook_order() {}
}
```
---
# 7.4 bring path to scope with use
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## use
:::info
:::
:::info
1. use 也有scope
2. 避免撞名
1. 把parent整個搬進來
2. as
3. reexport
:::
```rust=
use std::fmt;
use std::io;
fn function1() -> fmt::Result {
// --snip--
}
fn function2() -> io::Result<()> {
// --snip--
}
```
----
## use external package
e.g.
rand
```rust
use rand::Rng;
fn main() {
let mut rng = rand::thread_rng();
let random_number = rng.gen_range(1..101);
println!("Random number: {}", random_number);
}
```
----
:::info
nested path
use std::{cmp::Ordering, io};
:::
:::info
glob operator
use std::collections::*;
:::
---
# 7.5 sepearate module to different file
----
### 實戰時間
---
# chapter 8 common collections
* Vectors
* String
* HashMap
---
# 8.1 Vectors
----
```rust
let v: Vec<i32> = Vec::new();
let v = vec![1, 2, 3]; // rust will auto infer
let mut v = Vec::new();
v.push(5);
v.push(6);
v.push(7);
v.push(8);
let third: &i32 = &v[2]; <- 不存在會panic
println!("The third element is {third}");
let third: Option<&i32> = v.get(2); <- 回傳None若不存在
```
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# 8.2 Strings
----
複習
&str vs String
(no gb , scope(ownership), ref, mut)
----
常用String 方法
:::info
String::from
"apple".toString
:::
----
:::warning
Strings Are Not So Simple😢
:::
1. can't use index to access char(因為不同字編碼出的長度不同)
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# 8.3 Hash Maps
----
rust最類似 js object , python dict的存在
(by chatGpt)
```rust
use std::collections::HashMap;
let mut scores = HashMap::new();
scores.insert(String::from("Blue"), 10);
scores.insert(String::from("Yellow"), 50);
let team_name = String::from("Blue");
let score = scores.get(&team_name).copied().unwrap_or(0);
```
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謝謝收看
---
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