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Rust Basics

Generic Types

Create a struct where 1 of their values could be any type
struct Wrapper<T> {
value: T,
}
impl<T> Wrapper<T> {
pub fn new(value: T) -> Self {
Wrapper { value }
}
}
Wrapper::new(42).value
Wrapper::new("Foo").value, "Foo"

Option, Some & None

The Option type means that the value might by of type Some (there is something) or None:
pub enum Option<T> {
None,
Some(T),
}
You can use functions such as is_some() or is_none() to check the value of the Option.

Macros

Macros are more powerful than functions because they expand to produce more code than the code you’ve written manually. For example, a function signature must declare the number and type of parameters the function has. Macros, on the other hand, can take a variable number of parameters: we can call println!("hello") with one argument or println!("hello {}", name) with two arguments. Also, macros are expanded before the compiler interprets the meaning of the code, so a macro can, for example, implement a trait on a given type. A function can’t, because it gets called at runtime and a trait needs to be implemented at compile time.
macro_rules! my_macro {
() => {
println!("Check out my macro!");
};
($val:expr) => {
println!("Look at this other macro: {}", $val);
}
}
fn main() {
my_macro!();
my_macro!(7777);
}
// Export a macro from a module
mod macros {
#[macro_export]
macro_rules! my_macro {
() => {
println!("Check out my macro!");
};
}
}

Iterate

// Iterate through a vector
let my_fav_fruits = vec!["banana", "raspberry"];
let mut my_iterable_fav_fruits = my_fav_fruits.iter();
assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
assert_eq!(my_iterable_fav_fruits.next(), None); // When it's over, it's none
// One line iteration with action
my_fav_fruits.iter().map(|x| capitalize_first(x)).collect()
// Hashmap iteration
for (key, hashvalue) in &*map {
for key in map.keys() {
for value in map.values() {

Recursive Box

enum List {
Cons(i32, List),
Nil,
}
let list = Cons(1, Cons(2, Cons(3, Nil)));

Conditionals

if

let n = 5;
if n < 0 {
print!("{} is negative", n);
} else if n > 0 {
print!("{} is positive", n);
} else {
print!("{} is zero", n);
}

match

match number {
// Match a single value
1 => println!("One!"),
// Match several values
2 | 3 | 5 | 7 | 11 => println!("This is a prime"),
// TODO ^ Try adding 13 to the list of prime values
// Match an inclusive range
13..=19 => println!("A teen"),
// Handle the rest of cases
_ => println!("Ain't special"),
}
let boolean = true;
// Match is an expression too
let binary = match boolean {
// The arms of a match must cover all the possible values
false => 0,
true => 1,
// TODO ^ Try commenting out one of these arms
};

loop (infinite)

loop {
count += 1;
if count == 3 {
println!("three");
continue;
}
println!("{}", count);
if count == 5 {
println!("OK, that's enough");
break;
}
}

while

let mut n = 1;
while n < 101 {
if n % 15 == 0 {
println!("fizzbuzz");
} else if n % 5 == 0 {
println!("buzz");
} else {
println!("{}", n);
}
n += 1;
}

for

for n in 1..101 {
if n % 15 == 0 {
println!("fizzbuzz");
} else {
println!("{}", n);
}
}
// Use "..=" to make inclusive both ends
for n in 1..=100 {
if n % 15 == 0 {
println!("fizzbuzz");
} else if n % 3 == 0 {
println!("fizz");
} else if n % 5 == 0 {
println!("buzz");
} else {
println!("{}", n);
}
}
// ITERATIONS
let names = vec!["Bob", "Frank", "Ferris"];
//iter - Doesn't consume the collection
for name in names.iter() {
match name {
&"Ferris" => println!("There is a rustacean among us!"),
_ => println!("Hello {}", name),
}
}
//into_iter - COnsumes the collection
for name in names.into_iter() {
match name {
"Ferris" => println!("There is a rustacean among us!"),
_ => println!("Hello {}", name),
}
}
//iter_mut - This mutably borrows each element of the collection
for name in names.iter_mut() {
*name = match name {
&mut "Ferris" => "There is a rustacean among us!",
_ => "Hello",
}
}

if let

let optional_word = Some(String::from("rustlings"));
if let word = optional_word {
println!("The word is: {}", word);
} else {
println!("The optional word doesn't contain anything");
}

while let

let mut optional = Some(0);
// This reads: "while `let` destructures `optional` into
// `Some(i)`, evaluate the block (`{}`). Else `break`.
while let Some(i) = optional {
if i > 9 {
println!("Greater than 9, quit!");
optional = None;
} else {
println!("`i` is `{:?}`. Try again.", i);
optional = Some(i + 1);
}
// ^ Less rightward drift and doesn't require
// explicitly handling the failing case.
}

Traits

Create a new method for a type
trait AppendBar {
fn append_bar(self) -> Self;
}
impl AppendBar for String {
fn append_bar(self) -> Self{
format!("{}Bar", self)
}
}
let s = String::from("Foo");
let s = s.append_bar();
println!("s: {}", s);

Tests

#[cfg(test)]
mod tests {
#[test]
fn you_can_assert() {
assert!(true);
assert_eq!(true, true);
assert_ne!(true, false);
}
}

Threading

Arc

An Arc can use Clone to create more references over the object to pass them to the threads. When the last reference pointer to a value is out of scope, the variable is dropped.
use std::sync::Arc;
let apple = Arc::new("the same apple");
for _ in 0..10 {
let apple = Arc::clone(&apple);
thread::spawn(move || {
println!("{:?}", apple);
});
}

Threads

In this case we will pass the thread a variable it will be able to modify
fn main() {
let status = Arc::new(Mutex::new(JobStatus { jobs_completed: 0 }));
let status_shared = Arc::clone(&status);
thread::spawn(move || {
for _ in 0..10 {
thread::sleep(Duration::from_millis(250));
let mut status = status_shared.lock().unwrap();
status.jobs_completed += 1;
}
});
while status.lock().unwrap().jobs_completed < 10 {
println!("waiting... ");
thread::sleep(Duration::from_millis(500));
}
}