Transprogrammer

The struct Player and impl Player works as a class, with the difference that the struct block defines the attributes, e.g. position, and the impl defines the methods, e.g. move operation, as you figured out.

What Rust does not have is inheritence like you do for classes, instead you have traits.

Say you have a vector class. You will need some objects of rotating vectors, some objects of translation vectors, and some objects that can do both rotation and translation. You do a subclass of this vector class for rotating vectors, you make another subclass for translating vectors... you know what? Maybe all rotating vectors have to be also translating vectors, because you sometimes need a subclass which needs both. Ok. Or something like that might be your solution.

In Rust you'd instead define a rotation and translation trait, by saying structs dressed in this trait must have a method taking this and that argument, returning this and that. You make an impl block defining what these methods should look like for your vectors. You can dress one struct in several traits, so you have one struct which you give both the rotation and translation trait.

The bonus with traits now is now that later you realize that, ah, not only my pure vectors needs to be able to rotate. My Car struct needs to rotate, or my Planet struct, whatever. Great, you have a trait you can give to those structs and it will have the same methods as your rotating pure vectors.

I'm not a proper programmer, so this may all be a bit misleading. This is just how I think about it when I'm using Rust.

The Player-impl with a self-parameter can only be used together with a Player-struct.

Example:

struct Example {
    field: u8,
}

impl Example {
    fn new(field: u8) -> Self {
        Self {
            field,
        }
    }

    fn get_field(self) -> u8 {
        self.field
    }
}

// Usage
let example = Example::new(1); // doesn't need an instance to be called

let field = example.get_field(); // needs an instance to be called

let field = Example::get_field(example); // equivalent to the previous call

With reservations for that this code might not compile 100%. Anyway, I hope that clears it up.

You cannot combine them, but you can simply write them below each other. It makes no difference.

The biggest reason why they are in separate blocks, is because you can have multiple such impl-blocks, including in other files.

This is, for example, really useful, if you've got a model data type that's used in lots of places and you don't want to put the de-/serialization logic for it into the same file where that data type is declared.
You may not want that, because it's ugly boilerplate code or because that de-/serialization logic require dependencies, which you don't want to include everywhere where that model type is used. (The latter only becomes relevant for larger applications, which consist out of multiple sub-projects.)

They're separate blocks, but they're talking about the same type. struct deals with the data, impl deals with associated functions/methods/constants. If you implement a trait, you'd write yet another block like impl Trait for Player { [the stuff required by the trait, like an interface]}

trait Position {
    fn get_pos(&self) -> (f64, f64);
}

struct Player {
    x: f64,
    y: f64,
}

impl Player {
    const SOME_CONSTANT: usize = 42;
    fn not_associated_with_trait(&mut self) {
        self.x += 1.0;
    }
}

impl Foo for Player {
    fn get_pos(&self) -> (f64, f64) {
        return (self.x, self.y);
    }
}