192. impl Into — Take Owned or Borrowed Without an Extra Allocation

Tue, 09 Jun 2026 17:00:00 +0100

Bite 191 said: if you only read the argument, take &str. But what if you need to store it? Taking &str and calling .to_owned() always allocates — even when the caller handed you a String it was about to throw away. impl Into<String> fixes that.

191. Accept &str, Not String — Take the Most General Borrow

Tue, 09 Jun 2026 09:00:00 +0100

A function that takes String forces every caller holding a &str to allocate just to call you. Take &str instead — and &[T] over &Vec<T> — and deref coercion lets everyone in for free.

Api-Design on rustbites

192. impl Into — Take Owned or Borrowed Without an Extra Allocation

191. Accept &str, Not String — Take the Most General Borrow