rust cheatsheat

rust_cheatsheat.md

Run and install

Run src.main.rs or src.lib

cargo run

Run from examples folder

add my_file.rs in examples/my_file.rs

cargo run --example my_file

Create new lib

cargo new todo --lib

Run a file

Create a file in src/bin/file.rs Run it using

cargo run --bin file

---

Common language principles

Variables

Immutable by default

let x = 5;
x = 6; // <-- will throw error

let mut x = 5;
x = 6; // ok

Constants

const MYCONST: u32 = 60 * 60;

Shadowing

let x = 5; // 5
let x = 5 + 33; // 6 
{
    let x = x * 2; // 12
}

Tuple

let tup: (i32, f64, u8) = (500, 6.2, 1);

Array

let a: [i32; 5] = [1,2,3,4,5];
let a: [3; 5]; // [3,3,3,3,3]

List

Create a new list of int 32

let v: Vec<i32> = Vec::new();
// same as
let v = vec![1, 2, 3];

Updating elements

let mut v = Vec::new();
v.push(5);

Dropping elements

{
    let v = vec![1, 2, 3, 4];
    // do stuff with v
} // <  v goes out of scope and is freed here

Access element

let v = vec![1, 2, 3, 4, 5];
let third: &i32 = &v[2]; // access 3rd element

match v.get(2) { // access 3rd element
    Some(third) => println!("The third element is {}", third),
    None => println!("There is no third element."),
}

Enums

Declaration

enum Work {
    Civilian,
    Soldier,
}

use a matcher expression (switch like)

// Automatically `use` each name inside `Work`.
use crate::Work::*;

match status {
    // Note the lack of scoping because of the explicit `use` above.
    Rich => println!("The rich have lots of money!"),
    Poor => println!("The poor have no money..."),
}

Structs

#[derive(Debug)]
struct Rectangle {
    width: u32,
    height: u32,
}

impl Rectangle {
    fn area(&self) -> u32 {
        self.width * self.height
    }
}

Conditions

If statement

if number < 10 {
    //...            
} else if number > 12 {
    //...            
} else {
    //...            
}

If statement with assignement

let number = if condition {5} else {6};

Lifetime and

when we see a struct with a lifetime type-parameter it refers to the lifetimes of the references owned by this struct and nothing else.

pub struct Project<'a> {
    project_repository: &'a ProjectRepository,
    pub title: String,
}

impl<'a> Project<'a> {
    pub fn create(project_repository: &'a ProjectRepository, title: String) -> Self {
        Self {
            title,
            project_repository,
        }
    }
}

Loops

For loop

for i in 0..10 {
    //...            
}

While loop

while n < 10 {
    //...            
}

infinite loop

loop {
    if remain == 9 {
        break;
    }
}
// break, continue keyworks works

Create a module

pub mod mymodule {
    pub fn my_function1() {} // public accessible function
    
    fn my_function1() {} // private function
}

Attributes

InnerAttribute : # ! [ Attr ]
OuterAttribute : # [ Attr ]

// General metadata applied to the enclosing module or crate.
#![crate_type = "lib"]

// A function marked as a unit test
#[test]
fn test_foo() {  /* ... */}

Type alias

type Point = (u8, u8);
let p: Point = (41, 68);

Traits

A trait describes an abstract interface that types can implement.

trait NonDispatchable {
    // Non-methods cannot be dispatched.
    fn foo() where Self: Sized {}
    // Self type isn't known until runtime.
    fn returns(&self) -> Self where Self: Sized;
    // `other` may be a different concrete type of the receiver.
    fn param(&self, other: Self) where Self: Sized {}
    // Generics are not compatible with vtables.
    fn typed<T>(&self, x: T) where Self: Sized {}
}

struct S;
impl NonDispatchable for S {
    fn returns(&self) -> Self where Self: Sized { S }
}
let obj: Box<dyn NonDispatchable> = Box::new(S);
obj.returns(); // ERROR: cannot call with Self return
obj.param(S);  // ERROR: cannot call with Self parameter
obj.typed(1);  // ERROR: cannot call with generic type

Add copy and clone

First option add copy or clone trait

#[derive(Copy, Clone)]
struct Point {
   x: i32,
   y: i32,
}

You can also implement Copy and Clone manually:

struct MyStruct;

impl Copy for MyStruct { }

impl Clone for MyStruct {
    fn clone(&self) -> MyStruct {
        *self
    }
}

String manipulation

Format a string:

format!("{0}:{1}", self.app.url, self.app.port)

Read file / io

Read a file a return it as object

pub fn from_file(path: &'static str) -> Self {
    let config = fs::read_to_string(path).unwrap();
    serde_json::from_str(&config).unwrap()
}

Advanced borowing

• Cell // A mutable memory location.
• RefCell // A mutable memory ref location.
• Arc // shares memory ref between thread

Advanced function

Call a function as parameter

fn do_twice(f: fn(i32) -> i32, arg: i32) -> i32 {
    f(arg) + f(arg)
}

Packages

Watch changes

cargo install systemfd cargo-watch
systemfd --no-pid -s http::PORT -- cargo watch -x run

install these extensions for a great experience

code --install-extension matklad.rust-analyzer
code --install-extension vadimcn.vscode-lldb