[英]what does lifetime without a variable attached mean?
fn hello<'a>() {}
In rust, can a function have its own lifetime?在 rust 中,function 可以有自己的生命周期吗? I ran into a piece of code as below我遇到了一段代码如下
struct Hi {}
async fn wrapper<'a, F, Fut>(f: F)
where
Fut: Future<Output = ()>,
F: FnOnce(&'a mut Hi) -> Fut{
}
but couldn't understand what lifetime 'a could mean here...但无法理解 life 'a 在这里可能意味着什么......
can a function have its own lifetime? function 可以有自己的寿命吗?
Functions don't have lifetimes;函数没有生命周期; references do.参考资料。 But you can have a reference to a function.但是您可以参考 function。 And you can have a lifetime as a parameter of a function.您可以将生命周期作为 function 的参数。
couldn't understand what lifetime
'a
could mean here.无法理解 life'a
在这里可能意味着什么。
It just means it's a mutably borrowed parameter of closure with lifetime &'a
.这只是意味着它是一个可变借用的闭包参数,带有生命周期&'a
。
In essence, async fn wrapper<F, Fut>(f: F)
behaves the same, since &' a
can be elided.本质上, async fn wrapper<F, Fut>(f: F)
的行为相同,因为&' a
可以省略。
It would be useful if, somewhere inside the function's code, you needed to say lifetime 'a
will outlive some lifetime 'b
.如果在函数代码中的某处需要说生命周期'a
将比生命周期'b
长,这将很有用。
For example:例如:
async fn wrapper<'a, 'b, F, Fut>(f: F, b: &'b Hi)
where
Fut: Future<Output = ()>,
F: FnOnce(&'a mut Hi) -> Fut,
'a : 'b
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