rust - 隐性特征容器的不适当生命周期

Question

该代码用于递归地迭代所包含的特征

trait Getter<'a>{
    fn get(&self, index:usize)->&'a dyn Getter<'a>;
}
struct GetterImpl{
    children: Vec<GetterImpl>
}

impl<'a> Getter<'a> for GetterImpl{
    fn get(&self, index: usize) -> &'a dyn Getter<'a> {
        self.children.get(index).unwrap()
    }
}

impl GetterImpl{
    pub fn create(&mut self, v: Vec<GetterImpl>){
        self.children = v;
    }
}

我收到错误消息:

error[E0495]: cannot infer an appropriate lifetime for lifetime parameter in function call due to conflicting requirements
  --> mytest/main/src/main.rs:10:23
   |
10 |         self.children.get(index).unwrap()
   |                       ^^^
   |
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 9:5...
  --> mytest/main/src/main.rs:9:5
   |
9  | /     fn get(&self, index: usize) -> &'a dyn Getter<'a> {
10 | |         self.children.get(index).unwrap()
11 | |     }
   | |_____^
note: ...so that reference does not outlive borrowed content
  --> mytest/main/src/main.rs:10:9
   |
10 |         self.children.get(index).unwrap()
   |         ^^^^^^^^^^^^^
note: but, the lifetime must be valid for the lifetime `'a` as defined on the impl at 8:6...
  --> mytest/main/src/main.rs:8:6
   |
8  | impl<'a> Getter<'a> for GetterImpl{
   |      ^^
= note: expected `&'a (dyn Getter<'a> + 'a)`
           found `&dyn Getter<'a>`
...

我不明白这个错误。容器的生命周期应该比包含的容器长吗？谢谢!

Answer 1

您只需要将&self方法中的get()都更改为&'a self，因为否则，借用了self的生命周期与'a无关。