如何解决如何返回对迭代器中字段的引用?
我需要在由 Iterator
方法返回的结构中保存对 next
字段的引用。然而,编译器无法为借用表达式推断合适的生命周期。
这在 Rust 的当前版本中是否可行,我该怎么做?
use std::collections::HashMap;
struct CellDataRef<'a> {
value: &'a str,}
struct Row<'a> {
data_ref: &'a HashMap<String,CellDataRef<'a>>,}
struct TableIterator<'a> {
data: HashMap<String,}
impl<'a> Iterator for TableIterator<'a> {
type Item = Row<'a>;
fn next(&mut self) -> Option<Self::Item> {
Some(Row {
data_ref: &self.data,})
}
}
编译器错误:
error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements
--> src/lib.rs:20:23
|
20 | data_ref: &self.data,| ^^^^^^^^^^
|
note: first,the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 18:5...
--> src/lib.rs:18:5
|
18 | fn next(&mut self) -> Option<Self::Item> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...so that reference does not outlive borrowed content
--> src/lib.rs:20:23
|
20 | data_ref: &self.data,| ^^^^^^^^^^
note: but,the lifetime must be valid for the lifetime `'a` as defined on the impl at 15:6...
--> src/lib.rs:15:6
|
15 | impl<'a> Iterator for TableIterator<'a> {
| ^^
note: ...so that the types are compatible
--> src/lib.rs:18:46
|
18 | fn next(&mut self) -> Option<Self::Item> {
| ______________________________________________^
19 | | Some(Row {
20 | | data_ref: &self.data,21 | | })
22 | | }
| |_____^
= note: expected `Iterator`
found `Iterator`
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。