multithreading - “closure may outlive the current function”用作参数

Question

我试图将函数作为参数传递并在线程内调用它。这是我要运行的代码:

use std::thread;

pub struct Image {
    pub data: Vec<u8>,
}

pub trait ImageHandler {
    fn get_image(&self) -> Option<Image>;
}

pub struct Window {
    pub id: usize,
}

impl ImageHandler for Window {
    fn get_image(&self) -> Option<Image> {
        None
    }
}

fn test(func: impl Fn() -> Option<Image> + Sync + Send + 'static) -> thread::JoinHandle<()> {
    thread::spawn(move || {
        let _image = func().unwrap();
    })
}

fn main() {
    let window = Window { id: 0 };
    test(&|| window.get_image());
}

我收到以下错误:

error[E0373]: closure may outlive the current function, but it borrows `window`, which is owned by the current function
  --> src/main.rs:30:11
   |
30 |     test(&|| window.get_image());
   |           ^^ ------ `window` is borrowed here
   |           |
   |           may outlive borrowed value `window`
   |
note: function requires argument type to outlive `'static`
  --> src/main.rs:30:5
   |
30 |     test(&|| window.get_image());
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
help: to force the closure to take ownership of `window` (and any other referenced variables), use the `move` keyword
   |
30 |     test(&move || window.get_image());
   |           ^^^^^^^

error[E0716]: temporary value dropped while borrowed
  --> src/main.rs:30:11
   |
30 |     test(&|| window.get_image());
   |     ------^^^^^^^^^^^^^^^^^^^^^-- temporary value is freed at the end of this statement
   |     |     |
   |     |     creates a temporary which is freed while still in use
   |     argument requires that borrow lasts for `'static`

我认为 Fn对于将其发送到线程应该是静态的，但是当我将其生存期更改为 'static时，它会提示。
我也不知道是否可以使用 ImageHandler作为参数。我不知道这一点。

Answer 1

如果闭包可以超过当前线程的生命周期，那么它应该拥有所需变量的所有权:

fn main() {
    let window = Window { id: 0 };
    test(move || window.get_image());
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=9cbf953b79e80e280156688d083f94fb有游乐场。

但是，由于(我想)这只是一个玩具示例，因此此修复程序可能适用于或可能不适用于您的实际用例。如果变得更加复杂，则可以尝试说服编译器，使您知道闭包不会超过当前线程的生命周期(可能使用辅助包装箱)，或者诉诸其他技术。