/// <summary>
/// Creates a reaction that operates on data of type T.
/// </summary>
/// <typeparam name="T">The type the reaction operates on.</typeparam>
/// <param name="sharedState">The shared state to use.</param>
/// <param name="expression">The expression that delivers a value.</param>
/// <param name="effect">The effect that is executed when the value changes.</param>
/// <param name="reactionOptions">The options to use for the reaction.</param>
/// <returns>An <see cref="IDisposable"/> instance that can be used to stop the reaction.</returns>
public static IDisposable Reaction <T>(this ISharedState sharedState, Func <Reaction, T> expression, Action <T, Reaction> effect, ReactionOptions <T> reactionOptions = null)
{
if (sharedState is null)
{
throw new ArgumentNullException(nameof(sharedState));
}
if (expression is null)
{
throw new ArgumentNullException(nameof(expression));
}
if (effect is null)
{
throw new ArgumentNullException(nameof(effect));
}
if (reactionOptions is null)
{
reactionOptions = new ReactionOptions <T>();
}
var name = reactionOptions.Name ?? $"Reaction@{sharedState.GetUniqueId()}";
var action = sharedState.CreateAction(
name + "effect",
reactionOptions.Context,
reactionOptions.ErrorHandler != null ? WrapErrorHandler(reactionOptions.ErrorHandler, effect) : effect);
var runSync = reactionOptions.Scheduler == null && reactionOptions.Delay == 0;
var firstTime = true;
var isScheduled = false;
T value = default;
Reaction reaction = null;
var equals =
reactionOptions.EqualityComparer != null ?
new Func <T, T, bool>(reactionOptions.EqualityComparer.Equals) :
new Func <T, T, bool>((x, y) => Equals(x, y));
var scheduler = CreateSchedulerFromOptions(reactionOptions, ReactionRunner);
#pragma warning disable CA2000 // Dispose objects before losing scope
#pragma warning disable IDE0067 // Dispose objects before losing scope
reaction = new Reaction(
sharedState,
name,
() =>
{
if (firstTime || runSync)
{
ReactionRunner().GetAwaiter().GetResult();
}
else if (!isScheduled)
{
isScheduled = true;
scheduler().GetAwaiter().GetResult();
}
}, reactionOptions.ErrorHandler);
#pragma warning restore IDE0067 // Dispose objects before losing scope
#pragma warning restore CA2000 // Dispose objects before losing scope
Task ReactionRunner()
{
isScheduled = false; // Q: move into reaction runner?
if (reaction.IsDisposed)
{
return(Task.CompletedTask);
}
var changed = false;
reaction.Track(() =>
{
var nextValue = expression(reaction);
changed = firstTime || !equals(value, nextValue);
value = nextValue;
});
if (firstTime && reactionOptions.FireImmediately)
{
action(value, reaction);
}
if (!firstTime && changed)
{
action(value, reaction);
}
if (firstTime)
{
firstTime = false;
}
return(Task.CompletedTask);
}
reaction.Schedule();
return(new DisposableDelegate(() => reaction.Dispose()));
}
/// <summary>
/// Creates a reaction that operates on data of type T.
/// </summary>
/// <typeparam name="T">The type the reaction operates on.</typeparam>
/// <param name="sharedState">The shared state to use.</param>
/// <param name="expression">The expression that delivers a value.</param>
/// <param name="effect">The effect that is executed when the value changes.</param>
/// <param name="reactionOptions">The options to use for the reaction.</param>
/// <returns>An <see cref="IDisposable"/> instance that can be used to stop the reaction.</returns>
/// <remarks>Only pass asynchronous effect functions that wrap state modifications in actions.</remarks>
public static IDisposable Reaction <T>(this ISharedState sharedState, Func <Reaction, T> expression, Func <T, Reaction, Task> effect, ReactionOptions <T> reactionOptions = null)
{
if (sharedState is null)
{
throw new ArgumentNullException(nameof(sharedState));
}
if (expression is null)
{
throw new ArgumentNullException(nameof(expression));
}
if (effect is null)
{
throw new ArgumentNullException(nameof(effect));
}
if (reactionOptions is null)
{
reactionOptions = new ReactionOptions <T>();
}
var name = reactionOptions.Name ?? $"Reaction@{sharedState.GetUniqueId()}";
var action = reactionOptions.ErrorHandler != null?WrapErrorHandler(reactionOptions.ErrorHandler, effect) : effect;
var runSync = reactionOptions.Scheduler == null && reactionOptions.Delay == 0;
var firstTime = true;
var isScheduled = false;
T value = default;
Reaction reaction = null;
var equals =
reactionOptions.EqualityComparer != null ?
new Func <T, T, bool>(reactionOptions.EqualityComparer.Equals) :
new Func <T, T, bool>((x, y) => Equals(x, y));
var scheduler = CreateSchedulerFromOptions(reactionOptions, async() =>
{
await ReactionRunner().ConfigureAwait(true);
});
#pragma warning disable CA2000 // Dispose objects before losing scope
#pragma warning disable IDE0067 // Dispose objects before losing scope
reaction = new Reaction(
sharedState,
name,
() =>
{
if (firstTime || runSync)
{
var taskScheduler = sharedState.GetTaskScheduler();
isScheduled = true;
Task.Factory.StartNew(
ReactionRunner,
CancellationToken.None,
TaskCreationOptions.DenyChildAttach,
taskScheduler).Unwrap().ContinueWith(
t =>
{
if (t.Exception != null)
{
reaction.ReportExceptionInReaction(t.Exception);
}
}, taskScheduler);
}
else if (!isScheduled)
{
var taskScheduler = sharedState.GetTaskScheduler();
isScheduled = true;
Task.Factory.StartNew(
scheduler,
CancellationToken.None,
TaskCreationOptions.DenyChildAttach,
taskScheduler).Unwrap().ContinueWith(
t =>
{
if (t.Exception != null)
{
reaction.ReportExceptionInReaction(t.Exception);
}
}, taskScheduler);
}
}, reactionOptions.ErrorHandler);
#pragma warning restore IDE0067 // Dispose objects before losing scope
#pragma warning restore CA2000 // Dispose objects before losing scope
async Task ReactionRunner()
{
isScheduled = false; // Q: move into reaction runner?
if (reaction.IsDisposed)
{
return;
}
var changed = false;
reaction.Track(() =>
{
var nextValue = expression(reaction);
changed = firstTime || !equals(value, nextValue);
value = nextValue;
});
if (firstTime && reactionOptions.FireImmediately)
{
await action(value, reaction).ConfigureAwait(true);
}
if (!firstTime && changed)
{
await action(value, reaction).ConfigureAwait(true);
}
if (firstTime)
{
firstTime = false;
}
}
reaction.Schedule();
return(new DisposableDelegate(() => reaction.Dispose()));
}