vector - 如何从另一个矢量制作盒装特征对象的矢量？

Question

我正在制作一个机器人。当机器人收到消息时，它需要检查所有命令是否触发了消息，如果是，则执行操作。

所以我在主结构中有一个命令向量(Command trait):

struct Bot {
    cmds: Vec<Box<Command>>,
}

一切都很好，直到我尝试列出触发命令并稍后在 (&self mut) 方法中使用它们:

let mut triggered: Vec<Box<command::Command>>;
for c in &self.cmds {
    if c.check(&message) {
        triggered.push(c.clone());
    }
}

错误:

bot.rs:167:44: 167:56 error: mismatched types:
 expected `Box<Command>`,
    found `&Box<Command>`
(expected box,
    found &-ptr) [E0308]

我在这里做错了什么？我尝试了很多但没有任何帮助。 最初我在做以下事情:

for c in &self.cmds {
    if c.check(&message) {
        c.fire(&message, self);
    }
}

但它给了我:

bot.rs:172:46: 172:50 error: cannot borrow `*self` as mutable because `self.cmds` is also borrowed as immutable [E0502]
bot.rs:172        

                 c.fire(&message, self);

所以我stackoverflowed它并得出上面的解决方案。

Answer 1

What am I doing wrong here? I tried a lot but nothing helps. Initially I was doing the following:

for c in &self.cmds {
    if c.check(&message) {
        c.fire(&message, self);
    }
}

如果 fire 函数不需要访问其他命令，一个选项是暂时用空向量替换 self.cmd:

trait Command {
    fn check(&self, message: &str) -> bool;
    fn fire(&mut self, bot: &Bot);
}

struct Bot {
    cmds: Vec<Box<Command>>,
}

impl Bot {
    fn test(&mut self, message: &str) {
        use std::mem;
        // replace self.cmds with a empty vector and returns the
        // replaced vector
        let mut cmds = mem::replace(&mut self.cmds, Vec::default());
        for c in &mut cmds {
            if c.check(message) {
                c.fire(self);
            }
        }
        // put back cmds in self.cmds
        mem::replace(&mut self.cmds, cmds);
    }
}

有other answers使用这种方法的。

---

如果 fire 确实需要访问 Bot 的某些字段，您可以只传递需要的字段而不是 self:

c.fire(self.others)