面试题：Rust结构体方法设计之高级特征与设计模式

// 定义连接状态枚举
enum ConnectionState {
    Disconnected,
    Connecting,
    Connected,
}

// 定义连接结构体
struct Connection {
    state: ConnectionState,
}

// 定义连接状态机的行为
trait ConnectionStateMachine {
    fn connect(&mut self);
    fn disconnect(&mut self);
    fn get_state_description(&self) -> &str;
}

// 为Connection实现ConnectionStateMachine特征
impl ConnectionStateMachine for Connection {
    fn connect(&mut self) {
        match self.state {
            ConnectionState::Disconnected => {
                self.state = ConnectionState::Connecting;
                println!("正在连接...");
            }
            ConnectionState::Connecting => {
                self.state = ConnectionState::Connected;
                println!("已连接");
            }
            ConnectionState::Connected => {
                println!("已经处于连接状态，无法重复连接");
            }
        }
    }

    fn disconnect(&mut self) {
        match self.state {
            ConnectionState::Connected => {
                // 特定的断开流程，例如发送断开请求等
                println!("正在执行断开流程...");
                self.state = ConnectionState::Disconnected;
                println!("已断开连接");
            }
            ConnectionState::Connecting => {
                println!("连接中，无法断开");
            }
            ConnectionState::Disconnected => {
                println!("已经处于断开状态，无法重复断开");
            }
        }
    }

    fn get_state_description(&self) -> &str {
        match self.state {
            ConnectionState::Disconnected => "断开连接",
            ConnectionState::Connecting => "正在连接",
            ConnectionState::Connected => "已连接",
        }
    }
}

fn main() {
    let mut conn = Connection {
        state: ConnectionState::Disconnected,
    };
    conn.connect();
    conn.connect();
    println!("当前状态描述: {}", conn.get_state_description());
    conn.disconnect();
    conn.disconnect();
}

代码说明

枚举定义：使用 enum 定义 ConnectionState 枚举，表示连接的三种状态。
结构体定义：Connection 结构体包含一个 state 字段，类型为 ConnectionState。
特征定义：ConnectionStateMachine 特征定义了三个方法：connect、disconnect 和 get_state_description。
特征实现：为 Connection 结构体实现 ConnectionStateMachine 特征，在 connect 和 disconnect 方法中，通过 match 语句处理不同状态间的转换，并防止无效转换。get_state_description 方法返回当前状态的描述信息。
主函数：在 main 函数中创建 Connection 实例，并调用相关方法进行状态转换和获取状态描述。

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面试题：Rust结构体方法设计之高级特征与设计模式

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代码说明