英文:
enum method not printing out the expected value
问题
以下是翻译好的部分：
"Could somone point out what I am doing wrong here? Why isn't the call() method printing the value of self, which should be hello?"
"有人能指出我在这里做错了什么吗？为什么call()方法不打印self的值，它应该是hello？"
enum Message {
Quit,
Move { x: i32, y: i32 },
Write(String),
ChangeColor(i32, i32, i32),
}
impl Message {
fn call(&self) {
println!("{:?}", self);
}
}
fn main() {
let m = Message::Write(String::from("Hello"));
m.call();
}
请注意，代码中的HTML转义字符已被移除。
英文:
Could somone point out what I am doing wrong here? Why isn't the call() method printing the value of self, which should be hello?
enum Message {
Quit,
Move { x: i32, y: i32 },
Write(String),
ChangeColor(i32, i32, i32),
}
impl Message {
fn call(&self) {
println!("{:?}", self);
}
}
fn main() {
let m = Message::Write(String::from("Hello"));
m.call();
}
答案1
得分: 3
Message 类型必须实现 Debug 特性，以提供 {:?} 和 {:#?} 格式化支持。可以使用 derive 属性宏来完成它。
#[derive(Debug)]
enum Message {
...
}
// 另一种方式是手动实现
impl Debug for Message {
...
}
英文:
Message type must implement the Debug trait which brings {:?} and {:#?} formatting support. It can be done with the help of the derive attribute macro.
#[derive(Debug)]
enum Message {
...
}
// the other way is a manual implementation
impl Debug for Message {
...
}
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