Rust if let 可选和比较条件

Question

我有很多这样的代码，"if let"为了清楚起见，我想用绑定替换我的情况

// contrived
fn maybe() -> Option<i32> { Some(1)}
let maybe_num_A = maybe();
let maybe_num_B = maybe();
...
match (maybe_num_A, maybe_num_B) {
  (Some(a) , Some(b)) if a > b => {
      .... 
  }
  _ => {} // don't care many times about the other matches that doesn't hold. how to get rid of this?
}

不确定将 let 与比较绑定的语法：

if let (Some(a),Some(b) = (maybe_num_A, maybe_num_B) ???&&??? a > b {
   ... 
}

Answer 1

如果您只是比较A和 ，B并且不一定需要绑定它们，您可以使用Rust 1.46.zip中的方法并对其应用 a ，例如：map_or

let a: Option<i32> = Some(42);
let b: Option<i32> = Some(-42);

if a.zip(b).map_or(false, |(a, b)| a > b) {
   // 42 is greater than -42
}

如果两个值中有一个是None，则默认为false。