CleanCut/ultimate_rust2

Question: Eat your cake and have it too!

Dajamante opened this issue · 3 comments

Dajamante commented

Dear Nathan,

Is it possible to change the From impl into an Into implementation? (impl Into<Cake> for Party)?
You said that From/Into were mirrors of each other.
Would that even make sense?

impl From<Party> for Cake {
    fn from(party: Party) -> Self {
        party.cake
    }
}
smell_cake(party);

pub fn smell_cake<T: Into<Cake>>(something: T) {
    println!("Hmm...something smells like a {:?} cake!", something.into());
}
CleanCut commented

If you implement:

From<Party> for Cake

then the standard library implements this for you automatically!

Into<Cake> for Party

If you would rather implement this ☝🏻 manually, you may. But implementing the Into will not get you a free implementation of From, so you'll have to implement them both manually if you want them both.

Does that answer your question?

Dajamante commented

Yes thank you it replies PartialEq 🙂.
Would it make sense to implement it the other way around (even with the extra into() function) or is it very not idiomatic?

CleanCut commented

The idiomatic thing to do is to implement the From trait, and then the Into trait is implemented for you. It is usually more idiomatic to use the Into trait when defining functions! Sort of weird, eh?

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