Easy Rust

cargo doc

You might have noticed that Rust documentation always looks almost the same. On the left side you can see structs and traits, code examples are on the right, etc. This is because you can automatically make documentation just by typing cargo doc.

Even making a project with nothing can help you learn about traits in Rust. For example, here are two structs that do almost nothing, and a fn main() that also does nothing.

struct DoesNothing {}
struct PrintThing {}

impl PrintThing {
    fn prints_something() {
        println!("I am printing something");
    }
}

fn main() {}

But if you type cargo doc --open, you can see a lot more information than you expected. First it shows you this:

Crate rust_book

Structs
DoesNothing
PrintThing

Functions
main

But if you click on one of the structs, it will show you a lot of traits that you didn't think were there:

Struct rust_book::DoesNothing
[+] Show declaration
Auto Trait Implementations
impl RefUnwindSafe for DoesNothing
impl Send for DoesNothing
impl Sync for DoesNothing
impl Unpin for DoesNothing
impl UnwindSafe for DoesNothing
Blanket Implementations
impl<T> Any for T
where
    T: 'static + ?Sized,
[src]
[+]
impl<T> Borrow<T> for T
where
    T: ?Sized,
[src]
[+]
impl<T> BorrowMut<T> for T
where
    T: ?Sized,
[src]
[+]
impl<T> From<T> for T
[src]
[+]
impl<T, U> Into<U> for T
where
    U: From<T>,
[src]
[+]
impl<T, U> TryFrom<U> for T
where
    U: Into<T>,
[src]
[+]
impl<T, U> TryInto<U> for T
where
    U: TryFrom<T>,

This is because of all the traits that Rust automatically makes for every type.

Then if we add some documentation comments you can see them when you type cargo doc.

/// This is a struct that does nothing
struct DoesNothing {}
/// This struct only has one method.
struct PrintThing {}
/// It just prints the same message.
impl PrintThing {
    fn prints_something() {
        println!("I am printing something");
    }
}

fn main() {}

Now it will print:

Crate rust_book
Structs
DoesNothing This is a struct that does nothing
PrintThing  This struct only has one method.
Functions
main

cargo doc is very nice when you use a lot of other people's crates. Because these crates are all on different websites, it can take some time to search them all. But if you use cargo doc, you will have them all in the same place on your hard drive.