事件驱动 vs 轮询:两种架构的代价对比

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /UnrealEngine.com/Temporary/Diagnostics }

patrol_flag_device := class(creative_device):

    @editable
    StopButton:button_device = button_device{}

    var ShouldStop:logic = false

    OnBegin<override>()<suspends>:void =
        StopButton.InteractedWithEvent.Subscribe(OnStop)
        Patrol()

    OnStop(Agent:agent):void =
        # 处理函数只做一件事:升旗
        set ShouldStop = true

    Patrol()<suspends>:void =
        loop:
            if (ShouldStop?):
                break
            Print("巡逻中……")
            # 每圈必须让出控制权,否则处理函数永远没机会跑
            Sleep(0.0)
        Print("巡逻结束")

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /UnrealEngine.com/Temporary/Diagnostics }
# event(t) 的 Signal / Await 来自 /Verse.org/Concurrency
using { /Verse.org/Concurrency }

patrol_race_device := class(creative_device):

    @editable
    StopButton:button_device = button_device{}

    StopEvent:event() = event(){}

    OnBegin<override>()<suspends>:void =
        StopButton.InteractedWithEvent.Subscribe(OnStop)
        race:
            block:
                loop:
                    Print("巡逻中……")
                    Sleep(1.0)
            block:
                # 这一臂安静地等信号;信号一到,它获胜
                StopEvent.Await()
        Print("巡逻结束")

    OnStop(Agent:agent):void =
        StopEvent.Signal()