活塞 GenericEvent 未为事件实现

Question

我正在尝试使用 piston_window(0.77.0) 库在 Rust 中编写游戏。从他们的 hello world example I thought I would start by separating of rendering logic into a method using Event as parameter since according to documentation 开始，它由 window.next().

返回

use piston_window::*;

pub struct UI<'a> {
    window: &'a mut PistonWindow,
}

impl <'a> UI<'a> {
    pub fn new(window: &mut PistonWindow) -> UI {
        UI {
            window,
        }
    }

    fn render(&self, event: &Event) {
        self.window.draw_2d(&event, |context, graphics| {
            clear([1.0; 4], graphics);
            rectangle(
                [1.0, 0.0, 0.0, 1.0],
                [0.0, 0.0, 100.0, 100.0],
                context.transform,
                graphics);
            });
    }

    pub fn run(&mut self) {
        use Loop::Render;
        use Event::Loop;
        while let Some(event) = self.window.next() {
            match event {
                Loop(Render(_)) => self.render(&event),
                _ => {}
            }
        }
    }
}

然而，这以错误结束：

self.window.draw_2d(&event, |context, graphics| {
the trait piston_window::GenericEvent is not implemented for &piston_window::Event

没有提取渲染方法的代码按预期工作。

 pub fn run(&mut self) {
     use Loop::Render;
     use Event::Loop;
     while let Some(event) = self.window.next() {
         match event {
             Loop(Render(_)) => {
                 self.window.draw_2d(&event, |context, graphics| {
                     clear([1.0; 4], graphics);
                     rectangle(
                         [1.0, 0.0, 0.0, 1.0],
                         [0.0, 0.0, 100.0, 100.0],
                         context.transform,
                         graphics);
                 });

             },
             _ => {}
         }
     }
 }

我怎样才能提取这个？有什么我忽略的吗？

Answer 1

event 变量的类型为 &Event，而不是 Event，因此您实际上是在尝试将 &&Event 传递给 window.draw_2d。 Event 实现了 GenericEvent 但 &Event 没有实现，这就是您看到该错误的原因。

您只需要做：

self.window.draw_2d(event, |context, graphics| {
  ...
}

而不是：

self.window.draw_2d(&event, |context, graphics| {
  ...
}

公平地说，Rust 编译器为您指明了正确的方向。当我编译你的代码时，完整的错误信息是：

error[E0277]: the trait bound `&piston_window::Event: piston_window::GenericEvent` is not satisfied
  --> src/main.rs:34:21
   |
34 |         self.window.draw_2d(&event, |context, graphics| {
   |                     ^^^^^^^ the trait `piston_window::GenericEvent` is not implemented for `&piston_window::Event`
   |
   = help: the following implementations were found:
             <piston_window::Event as piston_window::GenericEvent>

最后的 "help" 部分告诉你 piston_window::Event 确实有正确的实现，而前面的错误是说 &piston_window::Event没有。

活塞 GenericEvent 未为事件实现

Piston GenericEvent not implemented for Event

rust

rust-piston