[英]How can I structure/destructure an enum of enums?
I am running into issues when matching on an enum of enums. 在枚举匹配时出现问题。 The structure is similar to this:
结构类似于此:
enum WebEvent {
PageLoad,
PageUnload,
KeyPress(char),
Paste(String),
Click { x: i64, y: i64 },
}
enum KeyEvent {
UpPressed,
DownPressed,
}
enum Event {
WebEvent,
KeyEvent,
}
fn inspect(event: Event) {
match event {
Event::WebEvent::PageLoad => println!("page loaded"),
Event::WebEvent::PageUnload => println!("page unloaded"),
Event::WebEvent::KeyPress(c) => println!("pressed '{}'.", c),
Event::WebEvent::Paste(s) => println!("pasted \"{}\".", s),
Event::WebEvent::Click { x, y } => {
println!("clicked at x={}, y={}.", x, y);
}
Event::KeyEvent => {
println!("got a key event");
}
}
}
fn main() {
let pressed = WebEvent::KeyPress('x');
inspect(pressed);
}
This is the error I get from the compiler: 这是我从编译器得到的错误:
error[E0433]: failed to resolve. Not a module `WebEvent`
--> src/main.rs:20:16
|
20 | Event::WebEvent::PageLoad => println!("page loaded"),
| ^^^^^^^^ Not a module `WebEvent`
error[E0433]: failed to resolve. Not a module `WebEvent`
--> src/main.rs:21:16
|
21 | Event::WebEvent::PageUnload => println!("page unloaded"),
| ^^^^^^^^ Not a module `WebEvent`
error[E0433]: failed to resolve. Not a module `WebEvent`
--> src/main.rs:22:16
|
22 | Event::WebEvent::KeyPress(c) => println!("pressed '{}'.", c),
| ^^^^^^^^ Not a module `WebEvent`
error[E0433]: failed to resolve. Not a module `WebEvent`
--> src/main.rs:23:16
|
23 | Event::WebEvent::Paste(s) => println!("pasted \"{}\".", s),
| ^^^^^^^^ Not a module `WebEvent`
error[E0433]: failed to resolve. Not a module `WebEvent`
--> src/main.rs:24:16
|
24 | Event::WebEvent::Click { x, y } => {
| ^^^^^^^^ Not a module `WebEvent`
error[E0308]: mismatched types
--> src/main.rs:35:13
|
35 | inspect(pressed);
| ^^^^^^^ expected enum `Event`, found enum `WebEvent`
|
= note: expected type `Event`
found type `WebEvent`
What is the right way to structure/destructure an enum of enums? 什么是构造/分解枚举的正确方法? Is there any way I can do this?
有什么办法可以做到吗?
You forgot that enum variants are not types - you need to introduce wrappers in order for an enum to be able to contain other enums: 您忘记了枚举变量不是类型-您需要引入包装器才能使枚举能够包含其他枚举:
enum Event {
WebEvent(WebEvent),
KeyEvent(KeyEvent)
}
The rest is pretty straightforward: 其余的非常简单:
enum WebEvent {
PageLoad,
PageUnload,
KeyPress(char),
Paste(String),
Click { x: i64, y: i64 },
}
enum KeyEvent {
UpPressed,
DownPressed,
}
enum Event {
WebEvent(WebEvent),
KeyEvent(KeyEvent)
}
fn inspect(event: Event) {
if let Event::WebEvent(webevt) = event {
match webevt {
WebEvent::PageLoad => println!("page loaded"),
WebEvent::PageUnload => println!("page unloaded"),
WebEvent::KeyPress(c) => println!("pressed '{}'.", c),
WebEvent::Paste(s) => println!("pasted \"{}\".", s),
WebEvent::Click { x, y } => println!("clicked at x={}, y={}.", x, y)
}
} else {
println!("got a key event")
}
}
fn main() {
let pressed = Event::WebEvent(WebEvent::KeyPress('x')); // note the extra wrap here
inspect(pressed);
}
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