如何在结构的生命周期内“保管”变量?

这将编译并通过测试:

use std::io::Write;

/*
 * This transforms a writer into a writer where every write is prefixed
 * with a timestamp and terminated with a newline.
 */

struct Timestamper<T: Write> {
    writer: T,
}

impl<T: Write> Timestamper<T> {
    pub fn new(writer: T) -> Timestamper<T> {
        Timestamper { writer }
    }
    pub fn drop(self) -> T {
        self.writer
    }
}

impl<T: Write> Write for Timestamper<T> {
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        self.writer.write(b"timestamp ")?;
        let expected_size = self.writer.write(buf)?;
        self.writer.write(b"\n")?;
        std::io::Result::Ok(expected_size)
    }

    fn flush(&mut self) -> std::io::Result<()> {
        self.writer.flush()
    }
}


#[cfg(test)]
mod tests {
    use std::io::Write;
    use super::Timestamper;

    #[test]
    fn test_timestamper() {
        let buf = Vec::new(); // buffer to write into
        let mut timestamper = Timestamper::new(buf);
        let hello_len = timestamper.write(b"hello").unwrap();
        let world_len = timestamper.write(b"world").unwrap();
        assert_eq!(hello_len, 5);
        assert_eq!(world_len, 5);
        let buf2 = timestamper.drop();
        assert_eq!(buf2.as_slice(), b"timestamp hello\ntimestamp world\n");
    }
}

正在制作 drop() 方法,该方法返回 writer 对象,在Rust中惯用?

是 下降() 最终展开函数的正确名称?