是否可以将Option< Result< T，E>到结果<选项< T>，E>.不使用火柴?
问题描述：
我首先想到的是map Option，但是我不能从闭包内部使用try!. match语句看起来不必要，但是我不知道如何简化它.
My first thought is to map the Option, but I can't use try! from inside of the closure. The match statement looks unnecessary, but I can't figure out how to simplify it.
fn example<T, E>(val: Option<Result<T, E>>) -> Result<Option<T>, E> {
Ok(match val {
Some(v) => Some(v?),
None => None
})
}
答
在Rust 1.33中， transpose() 是稳定的，因此您可以调用它:
In Rust 1.33, transpose() is stable, so you can just call it:
fn main() {
let x: Result<Option<i32>, ()> = Ok(Some(5));
let y: Option<Result<i32, ()>> = Some(Ok(5));
assert_eq!(x, y.transpose());
}