[英]What does “expected value, found trait” mean?
I am trying to build a scene manager that lets you push scenes onto a stack. 我正在尝试构建一个场景管理器,使您可以将场景推送到堆栈中。 When each scene is popped off the stack, it is run until stopped and then we repeat.
当每个场景从堆栈中弹出时,它会一直运行直到停止,然后我们重复。
An example is a menu in a game; 一个例子是游戏菜单。 which is one scene.
这是一个场景。 When you close it, the game map behind it is another scene.
当您关闭它时,它后面的游戏地图是另一个场景。
pub trait Scene {
fn start(&mut self) {}
fn update(&mut self) {}
fn stop(&mut self) {}
fn is_active(&self) -> bool {
return false;
}
}
pub struct SceneManager {
scenes: Vec<Box<Scene>>,
}
impl SceneManager {
fn new<T>(scene: T) -> SceneManager
where
T: Scene + 'static,
{
SceneManager { scenes: vec![Box::new(scene)] }
}
}
#[cfg(test)]
mod tests {
use super::*;
struct Sample {
running: bool,
}
impl Scene for Sample {
fn start(&mut self) {
self.running = true;
}
fn update(&mut self) {
if self.running {
self.stop()
}
}
fn stop(&mut self) {
self.running = false;
}
fn is_active(&self) -> bool {
self.running
}
}
#[test]
fn test_is_running() {
let scene_manager = SceneManager::new(Scene);
}
}
The Scene
trait is implemented for some structure that contains some way to tell if that scene is running or not. Scene
特征是为某些结构实现的,该结构包含某种方式来指示该场景是否正在运行。 In this case, a structure called Sample
. 在这种情况下,称为
Sample
的结构。
You implement the Scene
for Sample
and then push that scene to the scene manager). 您实现
Scene
Sample
,然后将该场景推送到场景管理器)。
error[E0423]: expected value, found trait `Scene`
--> src/engine/scene.rs:48:47
|
48 | let scene_manager = SceneManager::new(Scene);
| ^^^^^ not a value
Not exactly sure what to do at this point. 目前还不确定要做什么。 How do I get my scene on to the "stack" of scenes?
如何将场景添加到场景的“堆栈”中? I implemented the
new
function of SceneManager
to take a type where the type matches a Scene
definition (if I understood that correctly). 我实现了
SceneManager
的new
功能,以采用与Scene
定义匹配的类型(如果我正确理解的话)。 This alleviates me of having to specify a specific size and thus allowing me to push it to the heap instead of the stack. 这减轻了我必须指定特定大小的麻烦,从而使我可以将其压入堆而不是堆栈。
What am I doing wrong and how do I alleviate the problem at hand and what does this even mean? 我在做错什么,如何减轻眼前的问题,这甚至意味着什么?
Here Scene
is the name for a trait, but SceneManager::new
accepts a value of type Scene
. 这里
Scene
是特征的名称,但是SceneManager::new
接受一个Scene
类型的值。 You will probably want to do this 您可能会想要这样做
let scene_manager = SceneManager::new(Sample { running: false });
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