UniRx尝试翻译下

101http://rxwiki.wikidot.com/101samples

昨天，隔壁大娘教了我五个字母，今天一兴奋，决定和机翻配合用下。不要问为什么全漏了，我倒是要会呀！！放一个鬼在这。

Func<Action<int>, Action<int[]>> iter = new Func<Action<int>,Action<int[]>>
(x => new Action<int[]>(y => { foreach (int i in y) x(i); }));
var OutputArray = iter(x => Console.WriteLine(x));
int[] data = { 1, 2, 3, 4, 5 };
OutputArray(data);

Why Rx?

通常，unity的网络操作需要使用到WWW和协程（Coroutine），但是，使用协程（Coroutine）对于异步操作而言不是一个好的办法，原因如下：

协程不能返回任何值，因为它的返回类型必须是IEnumerator。
协程不能够捕捉异常，因为yield return 声明不支持try-catch结构。

Introduction

下面的代码，通过UniRx的实现了双击操作：

var clickStream = Observable.EveryUpdate()
    .Where(_ => Input.GetMouseButtonDown(0));

clickStream.Buffer(clickStream.Throttle(TimeSpan.FromMilliseconds(250)))
    .Where(xs => xs.Count >= 2)
    .Subscribe(xs => Debug.Log("DoubleClick Detected! Count:" + xs.Count));

这个例子演示了以下的特征：

游戏循环作为事件流
事件流可以组合
合并自身事件流
基于时间操作处理很简单

Network operations

对异步网络操作使用ObservableWWW ，它的Get/Post 函数返回可预见可观测：

ObservableWWW.Get("http://google.co.jp/")
    .Subscribe(
        x => Debug.Log(x.Substring(0, 100)), // onSuccess
        ex => Debug.LogException(ex)); // onError

Rx可以组合并可以撤销，你也能通过LINQ表达式查询：

// composing asynchronous sequence with LINQ query expressions
var query = from google in ObservableWWW.Get("http://google.com/")
            from bing in ObservableWWW.Get("http://bing.com/")
            from unknown in ObservableWWW.Get(google + bing)
            select new { google, bing, unknown };

var cancel = query.Subscribe(x => Debug.Log(x));

// Call Dispose is cancel.
cancel.Dispose();

对所有的并行请求使用Observable.WhenAll ：

// Observable.WhenAll is for parallel asynchronous operation
// (It's like Observable.Zip but specialized for single async operations like Task.WhenAll)
var parallel = Observable.WhenAll(
    ObservableWWW.Get("http://google.com/"),
    ObservableWWW.Get("http://bing.com/"),
    ObservableWWW.Get("http://unity3d.com/"));

parallel.Subscribe(xs =>
{
    Debug.Log(xs[0].Substring(0, 100)); // google
    Debug.Log(xs[1].Substring(0, 100)); // bing
    Debug.Log(xs[2].Substring(0, 100)); // unity
});

获得进度信息：

// notifier for progress use ScheudledNotifier or new Progress<float>(/* action */)
var progressNotifier = new ScheduledNotifier<float>();
progressNotifier.Subscribe(x => Debug.Log(x)); // write www.progress

// pass notifier to WWW.Get/Post
ObservableWWW.Get("http://google.com/", progress: progressNotifier).Subscribe();

错误处理：

// If WWW has .error, ObservableWWW throws WWWErrorException to onError pipeline.
// WWWErrorException has RawErrorMessage, HasResponse, StatusCode, ResponseHeaders
ObservableWWW.Get("http://www.google.com/404")
    .CatchIgnore((WWWErrorException ex) =>
    {
        Debug.Log(ex.RawErrorMessage);
        if (ex.HasResponse)
        {
            Debug.Log(ex.StatusCode);
        }
        foreach (var item in ex.ResponseHeaders)
        {
            Debug.Log(item.Key + ":" + item.Value);
        }
    })
    .Subscribe();

Using with IEnumerators (Coroutines)

IEnumerator （协程）是unity原始的异步工具。UniRx 集成了协程并可观测，你能在协程里写异步代码，并使用UniRx编排，这是控制异步流的最佳办法。

// two coroutines

IEnumerator AsyncA()
{
    Debug.Log("a start");
    yield return new WaitForSeconds(1);
    Debug.Log("a end");
}

IEnumerator AsyncB()
{
    Debug.Log("b start");
    yield return new WaitForEndOfFrame();
    Debug.Log("b end");
}

// main code
// Observable.FromCoroutine converts IEnumerator to Observable<Unit>.
// You can also use the shorthand, AsyncA().ToObservable()

// after AsyncA completes, run AsyncB as a continuous routine.
// UniRx expands SelectMany(IEnumerator) as SelectMany(IEnumerator.ToObservable())
var cancel = Observable.FromCoroutine(AsyncA)
    .SelectMany(AsyncB)
    .Subscribe();

// you can stop a coroutine by calling your subscription's Dispose.
cancel.Dispose();

假如在Unity5.3，你能使用ToYieldInstruction 对协程观测。

IEnumerator TestNewCustomYieldInstruction()
{
    // wait Rx Observable.
    yield return Observable.Timer(TimeSpan.FromSeconds(1)).ToYieldInstruction();

    // you can change the scheduler(this is ignore Time.scale)
    yield return Observable.Timer(TimeSpan.FromSeconds(1), Scheduler.MainThreadIgnoreTimeScale).ToYieldInstruction();

    // get return value from ObservableYieldInstruction
    var o = ObservableWWW.Get("http://unity3d.com/").ToYieldInstruction(throwOnError: false);
    yield return o;

    if (o.HasError) { Debug.Log(o.Error.ToString()); }
    if (o.HasResult) { Debug.Log(o.Result); }

    // other sample(wait until transform.position.y >= 100) 
    yield return this.transform.ObserveEveryValueChanged(x => x.position).FirstOrDefault(p => p.y >= 100).ToYieldInstruction();
}

通常，我们需要协程返回一个值就必须使用回调，Observable.FromCoroutine 能转换协程通过可撤销的IObservable[T] 替代

// public method
public static IObservable<string> GetWWW(string url)
{
    // convert coroutine to IObservable
    return Observable.FromCoroutine<string>((observer, cancellationToken) => GetWWWCore(url, observer, cancellationToken));
}

// IObserver is a callback publisher
// Note: IObserver's basic scheme is "OnNext* (OnError | Oncompleted)?" 
static IEnumerator GetWWWCore(string url, IObserver<string> observer, CancellationToken cancellationToken)
{
    var www = new UnityEngine.WWW(url);
    while (!www.isDone && !cancellationToken.IsCancellationRequested)
    {
        yield return null;
    }

    if (cancellationToken.IsCancellationRequested) yield break;

    if (www.error != null)
    {
        observer.OnError(new Exception(www.error));
    }
    else
    {
        observer.OnNext(www.text);
        observer.OnCompleted(); // IObserver needs OnCompleted after OnNext!
    }
}

这里有一些更多的例子，接下来是一个多OnNext模式。

public static IObservable<float> ToObservable(this UnityEngine.AsyncOperation asyncOperation)
{
    if (asyncOperation == null) throw new ArgumentNullException("asyncOperation");

    return Observable.FromCoroutine<float>((observer, cancellationToken) => RunAsyncOperation(asyncOperation, observer, cancellationToken));
}

static IEnumerator RunAsyncOperation(UnityEngine.AsyncOperation asyncOperation, IObserver<float> observer, CancellationToken cancellationToken)
{
    while (!asyncOperation.isDone && !cancellationToken.IsCancellationRequested)
    {
        observer.OnNext(asyncOperation.progress);
        yield return null;
    }
    if (!cancellationToken.IsCancellationRequested)
    {
        observer.OnNext(asyncOperation.progress); // push 100%
        observer.OnCompleted();
    }
}

// usecase
Application.LoadLevelAsync("testscene")
    .ToObservable()
    .Do(x => Debug.Log(x)) // output progress
    .Last() // last sequence is load completed
    .Subscribe();

Using for MultiThreading

// Observable.Start is start factory methods on specified scheduler
// default is on ThreadPool
var heavyMethod = Observable.Start(() =>
{
    // heavy method...
    System.Threading.Thread.Sleep(TimeSpan.FromSeconds(1));
    return 10;
});

var heavyMethod2 = Observable.Start(() =>
{
    // heavy method...
    System.Threading.Thread.Sleep(TimeSpan.FromSeconds(3));
    return 10;
});

// Join and await two other thread values
Observable.WhenAll(heavyMethod, heavyMethod2)
    .ObserveOnMainThread() // return to main thread
    .Subscribe(xs =>
    {
        // Unity can't touch GameObject from other thread
        // but use ObserveOnMainThread, you can touch GameObject naturally.
        (GameObject.Find("myGuiText")).guiText.text = xs[0] + ":" + xs[1];
    });

DefaultScheduler

UniRx默认的基于时间操作使用Scheduler.MainThread作为他们的调度程序，这意味着大多数操作（除了Observable.Start）在单线程工作，所以ObserverOn 不需要并且线程安全措施可以忽略。这对于标准的RxNet实施并不相同，但是更合适Unity环境。

Scheduler.MainThread运行受时间缩放的影响，如果你想忽略时间缩放，使用Scheduler.MainThreadIgnoreTimeScale代替。

MonoBehaviour triggers

UniRx通过UniRx.Triggers能处理MonoBehavirour事件:

using UniRx;
using UniRx.Triggers; // need UniRx.Triggers namespace

public class MyComponent : MonoBehaviour
{
    void Start()
    {
        // Get the plain object
        var cube = GameObject.CreatePrimitive(PrimitiveType.Cube);

        // Add ObservableXxxTrigger for handle MonoBehaviour's event as Observable
        cube.AddComponent<ObservableUpdateTrigger>()
            .UpdateAsObservable()
            .SampleFrame(30)
            .Subscribe(x => Debug.Log("cube"), () => Debug.Log("destroy"));

        // destroy after 3 second:)
        GameObject.Destroy(cube, 3f);
    }
}

支持的触发器有：ObservableAnimatorTrigger, ObservableCollision2DTrigger, ObservableCollisionTrigger, ObservableDestroyTrigger, ObservableEnableTrigger, ObservableFixedUpdateTrigger, ObservableUpdateTrigger, ObservableLastUpdateTrigger, ObservableMouseTrigger, ObservableTrigger2DTrigger, ObservableTriggerTrigger, ObservableVisibleTrigger, ObservableTransformChangedTrigger, ObservableRectTransformTrigger, ObservableCanvasGroupChangedTrigger, ObservableStateMachineTrigger, ObservableEventTrigger.

这些通过在组件/游戏物体上扩展方法也可以跟容易的处理。这些方法自动注入ObservableTrigger 除了ObservableEventTrigger 和ObservableStateMachineTrigger

using UniRx;
using UniRx.Triggers; // need UniRx.Triggers namespace for extend gameObejct

public class DragAndDropOnce : MonoBehaviour
{
    void Start()
    {
        // All events can subscribe by ***AsObservable
        this.OnMouseDownAsObservable()
            .SelectMany(_ => this.UpdateAsObservable())
            .TakeUntil(this.OnMouseUpAsObservable())
            .Select(_ => Input.mousePosition)
            .Subscribe(x => Debug.Log(x));
    }
}

Creating custom triggers

处理Unity事件转到Observable是最好的方法，如果UniRx提供的标准触发器还不够，你能创建自定义触发器，为了证明，这里有一个uGUI长按触发器：

public class ObservableLongPointerDownTrigger : ObservableTriggerBase, IPointerDownHandler, IPointerUpHandler
{
    public float IntervalSecond = 1f;

    Subject<Unit> onLongPointerDown;

    float? raiseTime;

    void Update()
    {
        if (raiseTime != null && raiseTime <= Time.realtimeSinceStartup)
        {
            if (onLongPointerDown != null) onLongPointerDown.OnNext(Unit.Default);
            raiseTime = null;
        }
    }

    void IPointerDownHandler.OnPointerDown(PointerEventData eventData)
    {
        raiseTime = Time.realtimeSinceStartup + IntervalSecond;
    }

    void IPointerUpHandler.OnPointerUp(PointerEventData eventData)
    {
        raiseTime = null;
    }

    public IObservable<Unit> OnLongPointerDownAsObservable()
    {
        return onLongPointerDown ?? (onLongPointerDown = new Subject<Unit>());
    }

    protected override void RaiseOnCompletedOnDestroy()
    {
        if (onLongPointerDown != null)
        {
            onLongPointerDown.OnCompleted();
        }
    }
}

它能像标准触发器一样容易使用

var trigger = button.AddComponent<ObservableLongPointerDownTrigger>();

trigger.OnLongPointerDownAsObservable().Subscribe();

Observable Lifecycle Management

什么时候呼叫OnCompleted ？当使用UniRx时考虑订阅的生命周期管理是非常重要的。ObservableTriggers呼叫OnCompleted时，附加的游戏对象被破坏，其它静态产生方法（Observable.Timer, Observable.EveryUpdate, 等等）不会自动停止，并且它们的订阅应该手动管理。

Rx提供一些辅助方法，比如IDisposable.AddTo允许你一次销毁若干订阅。

// CompositeDisposable is similar with List<IDisposable>, manage multiple IDisposable
CompositeDisposable disposables = new CompositeDisposable(); // field

void Start()
{
    Observable.EveryUpdate().Subscribe(x => Debug.Log(x)).AddTo(disposables);
}

void OnTriggerEnter(Collider other)
{
    // .Clear() => Dispose is called for all inner disposables, and the list is cleared.
    // .Dispose() => Dispose is called for all inner disposables, and Dispose is called immediately after additional Adds.
    disposables.Clear();
}

如果你想在游戏对象销毁时自动销毁，使用AddTo（游戏对象/组件）

void Start()
{
    Observable.IntervalFrame(30).Subscribe(x => Debug.Log(x)).AddTo(this);
}

AddTo促进自动销毁，如果你需要在管线里特殊处理OnCompleted，使用TakeWhile, TakeUntil, TakeUntilDestroy 和TakeUntilDisable 替代：

Observable.IntervalFrame(30).TakeUntilDisable(this)
    .Subscribe(x => Debug.Log(x), () => Debug.Log("completed!"));

如果你处理事件，Repeat是一个重要但是危险的方法，可能会导致一个无限循环，所以小心处理：

using UniRx;
using UniRx.Triggers;

public class DangerousDragAndDrop : MonoBehaviour
{
    void Start()
    {
        this.gameObject.OnMouseDownAsObservable()
            .SelectMany(_ => this.gameObject.UpdateAsObservable())
            .TakeUntil(this.gameObject.OnMouseUpAsObservable())
            .Select(_ => Input.mousePosition)
            .Repeat() // dangerous!!! Repeat cause infinite repeat subscribe at GameObject was destroyed.(If in UnityEditor, Editor is freezed)
            .Subscribe(x => Debug.Log(x));
    }
}

UniRx提供额外的安全重复方法，RepeatSafe：如果连续的“OnComplete”触发重复停止。RepeatUntilDestroy(gameObject/component), RepeatUntilDisable(gameObject/component)当目标游戏对象被销毁时允许停止。

this.gameObject.OnMouseDownAsObservable()
    .SelectMany(_ => this.gameObject.UpdateAsObservable())
    .TakeUntil(this.gameObject.OnMouseUpAsObservable())
    .Select(_ => Input.mousePosition)
    .RepeatUntilDestroy(this) // safety way
    .Subscribe(x => Debug.Log(x));

如果订阅在订阅中，不分离事件的话。UniRx保证观察热点有持久的异常，这是怎么一回事？

button.OnClickAsObservable().Subscribe(_ =>
{
    // If throws error in inner subscribe, but doesn't detached OnClick event.
    ObservableWWW.Get("htttp://error/").Subscribe(x =>
    {
        Debug.Log(x);
    });
});

这种行为有时是有用的，如用户事件处理。

所有类的实例提供了一个observeeveryvaluechanged方法，观察每一帧值的改变。

// watch position change
this.transform.ObserveEveryValueChanged(x => x.position).Subscribe(x => Debug.Log(x));

这是非常有用的。如果观察的目标是一个游戏对象，当目标被摧毁它将停止观察，呼叫onCompleted。如果观察的目标是一个普通的C #对象，OnCompleted被垃圾回收。

Converting Unity callbacks to IObservables

对于异步操作使用主题（或异步主题）

public class LogCallback
{
    public string Condition;
    public string StackTrace;
    public UnityEngine.LogType LogType;
}

public static class LogHelper
{
    static Subject<LogCallback> subject;

    public static IObservable<LogCallback> LogCallbackAsObservable()
    {
        if (subject == null)
        {
            subject = new Subject<LogCallback>();

            // Publish to Subject in callback
            UnityEngine.Application.RegisterLogCallback((condition, stackTrace, type) =>
            {
                subject.OnNext(new LogCallback { Condition = condition, StackTrace = stackTrace, LogType = type });
            });
        }

        return subject.AsObservable();
    }
}

// method is separatable and composable
LogHelper.LogCallbackAsObservable()
    .Where(x => x.LogType == LogType.Warning)
    .Subscribe();

LogHelper.LogCallbackAsObservable()
    .Where(x => x.LogType == LogType.Error)
    .Subscribe();

在Unity5，Application.RegisterLogCallback 移除 in favor of Application.logMessageReceived,所以我们简单的使用 Observable.FromEvent.

public static IObservable<LogCallback> LogCallbackAsObservable()
{
    return Observable.FromEvent<Application.LogCallback, LogCallback>(
        h => (condition, stackTrace, type) => h(new LogCallback { Condition = condition, StackTrace = stackTrace, LogType = type }),
        h => Application.logMessageReceived += h, h => Application.logMessageReceived -= h);
}

Stream Logger

// using UniRx.Diagnostics;

// logger is threadsafe, define per class with name.
static readonly Logger logger = new Logger("Sample11");

// call once at applicationinit
public static void ApplicationInitialize()
{
    // Log as Stream, UniRx.Diagnostics.ObservableLogger.Listener is IObservable<LogEntry>
    // You can subscribe and output to any place.
    ObservableLogger.Listener.LogToUnityDebug();

    // for example, filter only Exception and upload to web.
    // (make custom sink(IObserver<EventEntry>) is better to use)
    ObservableLogger.Listener
        .Where(x => x.LogType == LogType.Exception)
        .Subscribe(x =>
        {
            // ObservableWWW.Post("", null).Subscribe();
        });
}

// Debug is write only DebugBuild.
logger.Debug("Debug Message");

// or other logging methods
logger.Log("Message");
logger.Exception(new Exception("test exception"));

Unity-specific Extra Gems

// Unity's singleton UiThread Queue Scheduler
Scheduler.MainThreadScheduler 
ObserveOnMainThread()/SubscribeOnMainThread()

// Global StartCoroutine runner
MainThreadDispatcher.StartCoroutine(enumerator)

// convert Coroutine to IObservable
Observable.FromCoroutine((observer, token) => enumerator(observer, token)); 

// convert IObservable to Coroutine
yield return Observable.Range(1, 10).ToYieldInstruction(); // after Unity 5.3, before can use StartAsCoroutine()

// Lifetime hooks
Observable.EveryApplicationPause();
Observable.EveryApplicationFocus();
Observable.OnceApplicationQuit();

Framecount-based time operators

UniRx提供一些基于帧数的时间操作：

Method
EveryUpdate
EveryFixedUpdate
EveryEndOfFrame
EveryGameObjectUpdate
EveryLateUpdate
ObserveOnMainThread
NextFrame
IntervalFrame
TimerFrame
DelayFrame
SampleFrame
ThrottleFrame
ThrottleFirstFrame
TimeoutFrame
DelayFrameSubscription

例如：延迟调用一次：

Observable.TimerFrame(100).Subscribe(_ => Debug.Log("after 100 frame"));

每个方法执行的顺序是

EveryGameObjectUpdate(in MainThreadDispatcher's Execution Order) ->
EveryUpdate -> 
EveryLateUpdate -> 
EveryEndOfFrame

如果Caller在MainThreadDispatcher.Update前被呼叫，EveryGameObjectUpdate 调用同一帧（我建议MainThreadDispatcher 第一个被呼叫(ScriptExecutionOrder makes -32000)

EveryLateUpdate, EveryEndOfFrame 调用同一帧。

EveryUpdate, 调用下一帧。.

MicroCoroutine

Microcoroutine内存高效并快速协程的worker，这个实现基于Unity 10000次轮询。避免管理-非管理开销，所以快10倍。基于帧时间操作和ObserveEveryValueChanged时MicroCoroutine 自动使用。

如果你想使用MicroCoroutine 代替标准的unity协程，使用MainThreadDispatcher.StartUpdateMicroCoroutine 或 Observable.FromMicroCoroutine.

int counter;

IEnumerator Worker()
{
    while(true)
    {
        counter++;
        yield return null;
    }
}

void Start()
{
    for(var i = 0; i < 10000; i++)
    {
        // fast, memory efficient
        MainThreadDispatcher.StartUpdateMicroCoroutine(Worker());

        // slow...
        // StartCoroutine(Worker());
    }
}

Image title

MicroCoroutine的限制，仅支持yield return null并且更新时间在开始方法里被确定(StartUpdateMicroCoroutine, StartFixedUpdateMicroCoroutine, StartEndOfFrameMicroCoroutine).如果你结合其他的IObservable，你能像结束一样检测完成属性。

IEnumerator MicroCoroutineWithToYieldInstruction()
{
    var www = ObservableWWW.Get("http://aaa").ToYieldInstruction();
    while (!(www.HasResult || www.IsCanceled || www.HasError))
    {
        yield return null;
    }

    if (www.HasResult)
    {
        UnityEngine.Debug.Log(www.Result);
    }
}

uGUI Integration

views63 2016-11-05

UniRx 还是不敢引入项目里面，很多同事不适应。开头那个差点没看懂
写成这样会简洁一点
Func iter = x => y => { foreach (int i in y) x(i); };
评论里Func 那些会被吞掉？
最近由 views63 修改于：2016-11-05 15:34:21
- kuaile 2016-11-05
  
  @views63：初学中，还没有碰到吞掉的情况，如果是公司的项目，稳定肯定是第一位的。不过自己确实很喜欢链式的写法，干净整洁，可能因为不是程序出生的缘故，特别怕复杂。
- views63 2016-11-06
  
  @kuaile：评论里是被吞掉了我那边写着是你文章开头那个函数签名，现在看到的只有 func，Action> 了。我们项目里面都规定不能用 var ，扩展方法等都限制使用。基本上停留在C# 2.0 的语法
- kuaile 2016-11-06
  
  @views63：这个练习恰恰相反，整个游戏建立在一条系统链上，系统链上的每一个系统都需要单一职责，短小精炼，其外的代码全以扩展的方式给出。整个框架也没有两个类，看起很多类，但每个都是局部类，还是很颠覆的——类不要过大。
  自己又天性好奇，总想尝试新的东西，探索的乐趣就在其中。
kuaile 2016-11-06

果然会吞掉Func iter = x => y => { foreach (int i in y) x(i); }; 确实简洁很多。
最近由 kuaile 修改于：2016-11-06 07:57:12
- eastecho 2016-11-07
  
  @kuaile：是说评论里面的代码被吞掉吧？记得是为了安全考虑
- kuaile 2016-11-07
  
  @eastecho：是的，评论会吞掉。

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