공유 타입
Associated types are placeholder types which are supplied by the trait implementation.
#[derive(Debug)] struct Meters(i32); #[derive(Debug)] struct MetersSquared(i32); trait Multiply { type Output; fn multiply(&self, other: &Self) -> Self::Output; } impl Multiply for Meters { type Output = MetersSquared; fn multiply(&self, other: &Self) -> Self::Output { MetersSquared(self.0 * other.0) } } fn main() { println!("{:?}", Meters(10).multiply(&Meters(20))); }
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Associated types are sometimes also called "output types". The key observation is that the implementer, not the caller, chooses this type.
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Many standard library traits have associated types, including arithmetic operators and
Iterator
.