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Update ch19-02-advanced-lifetimes.md

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@ -119,12 +119,7 @@ body at 15:55...
通过了解`parse`的实现, 我们明白了`parse`的返回值被绑定到`Parser`的唯一原因是因为它引用了`Prser`中的`Context`, 也就是对一个字符串切片的引用, 所以它的生命周期才是`parse_context`需要关心的字符串切片的真正的生命周期. 我们需要告诉 Rust 在`Context`中的字符串切片和对`Parser`中的`Context`的引用有不同的生命周期, 我们还要告诉 Rust `parse_context` 函数的返回值被绑定到了`Context`中的字符串切片的生命周期. 通过了解`parse`的实现, 我们明白了`parse`的返回值被绑定到`Parser`的唯一原因是因为它引用了`Prser`中的`Context`, 也就是对一个字符串切片的引用, 所以它的生命周期才是`parse_context`需要关心的字符串切片的真正的生命周期. 我们需要告诉 Rust 在`Context`中的字符串切片和对`Parser`中的`Context`的引用有不同的生命周期, 我们还要告诉 Rust `parse_context` 函数的返回值被绑定到了`Context`中的字符串切片的生命周期.
We could try only giving `Parser` and `Context` different lifetime parameters 我们可以尝试像例 19-15 中显示的那样只给`Parser`和`Context`不同的生命周期参数. 我们选择了生命周期参数`'s`和`'c`, 这样可以很方便的区分哪个生命周期伴随`Context`中的字符串切片, 哪个生命周期伴随`Parser`中的`Context`引用. 注意这还不能完全修正问题, 但这是一个开始, 编译时我们就会明白为什么它还不够.
as shown in Listing 19-15. We've chosen the lifetime parameter names `'s` and
`'c` here to be clearer about which lifetime goes with the string slice in
`Context` and which goes with the reference to `Context` in `Parser`. Note that
this won't completely fix the problem, but it's a start and we'll look at why
this isn't sufficient when we try to compile.
```rust,ignore ```rust,ignore
struct Context<'s>(&'s str); struct Context<'s>(&'s str);
@ -144,8 +139,7 @@ fn parse_context(context: Context) -> Result<(), &str> {
} }
``` ```
<span class="caption">Listing 19-15: Specifying different lifetime parameters <span class="caption">例19-15: 给对字符串切片和对`Context`的引用指定不同的生命周期参数</span>
for the references to the string slice and to `Context`</span>
We've annotated the lifetimes of the references in all the same places that we We've annotated the lifetimes of the references in all the same places that we
annotated them in Listing 19-13, but used different parameters depending on annotated them in Listing 19-13, but used different parameters depending on