Golang状态模式实现复杂状态机示例

type ConnectionState interface {
    Connect(conn *Connection)
    Disconnect(conn *Connection)
    Send(conn *Connection, data string)
}

type Connection struct {
    state ConnectionState
}

func (c *Connection) SetState(state ConnectionState) {
    c.state = state
}

func (c *Connection) Connect()    { c.state.Connect(c) }
func (c *Connection) Disconnect() { c.state.Disconnect(c) }
func (c *Connection) Send(data string) { c.state.Send(c, data) }

func (c *Connection) GetCurrentState() string {
    switch c.state.(type) {
    case *DisconnectedState:
        return "Disconnected"
    case *ConnectingState:
        return "Connecting"
    case *ConnectedState:
        return "Connected"
    default:
        return "Unknown"
    }
}

type DisconnectedState struct{}

func (s *DisconnectedState) Connect(conn *Connection) {
    println("开始连接...")
    conn.SetState(&ConnectingState{})
}

func (s *DisconnectedState) Disconnect(conn *Connection) {
    println("已经断开，无需再断开")
}

func (s *DisconnectedState) Send(conn *Connection, data string) {
    println("无法发送：尚未连接")
}

type ConnectingState struct{}

func (s *ConnectingState) Connect(conn *Connection) {
    println("正在连接中，请勿重复连接")
}

func (s *ConnectingState) Disconnect(conn *Connection) {
    println("取消连接")
    conn.SetState(&DisconnectedState{})
}

func (s *ConnectingState) Send(conn *Connection, data string) {
    println("连接未完成，无法发送数据")
}

type ConnectedState struct{}

func (s *ConnectedState) Connect(conn *Connection) {
    println("已连接，无需再次连接")
}

func (s *ConnectedState) Disconnect(conn *Connection) {
    println("断开连接")
    conn.SetState(&DisconnectedState{})
}

func (s *ConnectedState) Send(conn *Connection, data string) {
    println("发送数据:", data)
}

func NewConnection() *Connection {
    return &Connection{state: &DisconnectedState{}}
}

func main() {
    conn := NewConnection()

    conn.Send("hello")        // 无法发送：尚未连接
    conn.Connect()            // 开始连接...
    conn.Send("hello")        // 连接未完成，无法发送数据
    conn.Disconnect()         // 取消连接
    conn.Connect()            // 开始连接...
    // 模拟进入已连接状态（实际可能由异步事件触发）
    conn.SetState(&ConnectedState{})
    conn.Send("world")        // 发送数据: world
    conn.Disconnect()         // 断开连接
}