在以下上下文中，如何解决“引用的生命周期比借用内容的生命周期更长”？

Question

我的 lib.rs 中有以下结构

pub enum ConfigurationSource {
    StringContent(String),
    FileContent(PathBuf)    
}

pub struct ConfigurationBuilder<'a> {
    config: Value,
    bundles: HashMap<&'a str, &'a Vec<ConfigurationSource>>    
}

impl<'a> ConfigurationBuilder<'a>{
    pub fn new(base_source: &ConfigurationSource) -> ConfigurationBuilder{
        let base_config: Value = from_str("{}").unwrap();

        let mut config_builder = ConfigurationBuilder{
            config: base_config,
            bundles: HashMap::new()
        };

        config_builder.merge_source(&base_source);

        return config_builder;
    }

    //more code here

    pub fn define_bundle(&mut self, bundle_key: &str, sources: &Vec<ConfigurationSource>){
        self.bundles.insert(bundle_key, sources);
    }
}

我不希望 ConfigurationBuilder 实例中的包 Hashmap 拥有传递给方法的bundle_keys 或sources define_bundle。

我在构建时收到以下两个编译错误

error[E0312]: lifetime of reference outlives lifetime of borrowed content...
  --> src\lib.rs:67:41
   |
67 |         self.bundles.insert(bundle_key, sources);
   |                                         ^^^^^^^
   |
note: ...the reference is valid for the lifetime 'a as defined on the impl at 27:1...
  --> src\lib.rs:27:1
   |
27 | / impl<'a> ConfigurationBuilder<'a>{
28 | |
29 | |     pub fn new(base_source: &ConfigurationSource) -> ConfigurationBuilder{
30 | |         let base_config: Value = from_str("{}").unwrap();
...  |
89 | |     }
90 | | }
   | |_^
note: ...but the borrowed content is only valid for the anonymous lifetime #3 defined on the method
 body at 66:5
  --> src\lib.rs:66:5
   |
66 | /     pub fn define_bundle(&mut self, bundle_key: &str, sources: &Vec<ConfigurationSource>){
67 | |         self.bundles.insert(bundle_key, sources);
68 | |     }
   | |_____^

error[E0312]: lifetime of reference outlives lifetime of borrowed content...
  --> src\lib.rs:67:29
   |
67 |         self.bundles.insert(bundle_key, sources);
   |                             ^^^^^^^^^^
   |
note: ...the reference is valid for the lifetime 'a as defined on the impl at 27:1...
  --> src\lib.rs:27:1
   |
27 | / impl<'a> ConfigurationBuilder<'a>{
28 | |
29 | |     pub fn new(base_source: &ConfigurationSource) -> ConfigurationBuilder{
30 | |         let base_config: Value = from_str("{}").unwrap();
...  |
89 | |     }
90 | | }
   | |_^
note: ...but the borrowed content is only valid for the anonymous lifetime #2 defined on the method
 body at 66:5
  --> src\lib.rs:66:5
   |
66 | /     pub fn define_bundle(&mut self, bundle_key: &str, sources: &Vec<ConfigurationSource>){
67 | |         self.bundles.insert(bundle_key, sources);
68 | |     }
   | |_____^

我究竟做错了什么？

Answer 1

您的输入参数define_bundle具有编译器不知道满足或超过为结构定义的生命周期的生命周期。

告诉编译器他们期望相同的生命周期可以解决问题：

pub fn define_bundle(&mut self, bundle_key: &'a str, sources: &'a Vec<ConfigurationSource>) {
    //                                       ^^----------------^^ same lifetimes as the struct fields expect
    self.bundles.insert(bundle_key, sources);
}