2

我有一个特点：

pub trait Plugin {
    type Error: error::Error;

    fn handle(&mut self, client: & Client, message: Message) -> Result<(), Self::Error>;
}

这个特性有很多实现（每个实现都包含一个特定的错误类型）：

impl ::Plugin for first::Plugin {
    type Error = first::Error;

    fn handle(&mut self, client: & Client, message: Message) -> first::Result<()> {
        ...
        Ok(())
    }
}

impl ::Plugin for second::Plugin {
    type Error = second::Error;

    fn handle(&mut self, client: & Client, message: Message) -> second::Result<()> {
        ...
        Ok(())
    }
}

我需要创建插件向量：

let mut plugins: Vec<Box<Plugin<Error=_>>> = vec![
    Box::new(first::Plugin::new()),
    Box::new(second::Plugin::new()),
];

但是代码抛出了这个错误：

error: type mismatch resolving `<plugins::first::Plugin<'_> as plugin::Plugin>::Error == plugins::second::error::Error`:

如何重新组织代码以创建impl trait Plugin包含关联类型（也是动态调度）的插件向量（动态调度impl trait error::Error）？

--

这是完整的代码：

fn main() {
    let mut plugins: Vec<Box<Plugin<Error = _>>> = vec![
        Box::new(first::Plugin::new()),
        Box::new(second::Plugin::new()),
    ];
}

pub trait Plugin {
    type Error: std::error::Error;

    fn handle(&mut self) -> Result<(), Self::Error>;
}

mod first {
    use std;

    pub struct Plugin;

    impl Plugin {
        pub fn new() -> Plugin {
            Plugin
        }
    }

    impl ::Plugin for Plugin {
        type Error = Error;

        fn handle(&mut self) -> Result<(), Error> {
            Ok(())
        }
    }

    #[derive(Debug)]
    pub struct Error;

    impl std::fmt::Display for Error {
        fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
            write!(f, "{}", "first error")
        }
    }

    impl std::error::Error for Error {
        fn description(&self) -> &str {
            "first error"
        }
    }
}

mod second {
    use std;

    pub struct Plugin;

    impl Plugin {
        pub fn new() -> Plugin {
            Plugin
        }
    }

    impl ::Plugin for Plugin {
        type Error = Error;

        fn handle(&mut self) -> Result<(), Error> {
            Ok(())
        }
    }

    #[derive(Debug)]
    pub struct Error;

    impl std::fmt::Display for Error {
        fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
            write!(f, "{}", "second error")
        }
    }

    impl std::error::Error for Error {
        fn description(&self) -> &str {
            "second error"
        }
    }
}

锈操场

4

0 回答 0