rust_naming_convension_examples/src/main.rs

use std::path::Path;

fn main() {

}

#[derive(Copy, Clone, Debug)]
struct CopyObject<'a> {
    pub val: &'a str,
}

struct AnObject {
    pub val: String,
}

struct TheOtherObject {
    pub val: Vec<u8>,
}

impl AnObject {

    // as_ borrowed (&self) -> borrowed (&[u8])
    fn as_bytes(&self) -> &[u8] {
        // because the underlying data structure of a String is a Vec<u8>, the as_bytes actually just returns this as a borrowed value, really just making this a dumb proxy, but it shows us what we want: as_ is just a view into the underlying data structure: nothing is copied, nothing new is created, it only exposes the underlying data: free as in free beer because we are just returning something that point to something else: a reference
        self.val.as_bytes()
    }

    // to_ borrowed (&self) -> borrowed (&[u8])
    fn to_guarded_bytes(&self) -> Option<&[u8]> {
        // this is really a dumb example, but it kind of proves the point: we convert our Target to a str. The input and output smells like the above as_ and the as_ is free, but this really isn't, because we are doing some expensive validation first
        let mut is_valid = true;

        for s in self.val.chars() {
            if s > 'b' && s < 'w' {
                is_valid = false;
                break;
            }
        }

        if is_valid {
            return Some(self.val.as_bytes());
        }

        None
    }

    // to_ borrowed (&self) -> owned (TheOtherObject) (non-copy types)
    fn to_guarded_object(&self) -> Option<TheOtherObject> {
        // This performs our previous check, and if everything is fine, it converts our object to the new object, simply creating it, and making some more to_ calls. Really expensive, but no copy is made of `self`
        let guarded_bytes = self.to_guarded_bytes();

        match guarded_bytes {
            Some(bytes) => {
                Some(TheOtherObject {val: bytes.to_vec()})
            },
            None => None
        }
    }
}

impl<'a> CopyObject<'a> {

    // to_ owned (self) -> owned (TheOtherObject) (copy types)
    fn to_object(self) -> TheOtherObject {
        // because self is not a reference, it is actually not consumed (likewise it isn't consumed when we do a &self ... yes we could do a &self here, but it kind of defeats the purpose of doing the example), but it is copied. The copy itself though is more expensive than just doing a reference. In our example, we are actually being quite expensive doing a to_vec conversion of our free as_ view

        TheOtherObject { val: self.val.as_bytes().to_vec()}
    }
}

// into_ owned -> owned (non-copy types)