/// <summary>
/// Creates an reaction that observes and runs the given predicate function
/// until it returns true. Once that happens, the given effect function
/// is executed and the reaction is deactivated.<br/>
/// <br/>
/// Returns a reaction, allowing you to cancel it manually.
/// </summary>
/// <param name="p">An observed predicate function.</param>
/// <param name="sideEffect">An effect function.</param>
/// <param name="exceptionHandler">A function that called when an exception is thrown while computing an reaction.</param>
/// <param name="debugName">Debug name for this reaction.</param>
/// <returns>Created reaction.</returns>
/// <example>
///
/// var counter = Atom.Value(1);
///
/// var reaction = Atom.When(
/// () => counter.Value == 10,
/// () => Debug.Log("Counter value equals 10")
/// );
///
/// </example>
public static Reaction When(
Func <bool> p,
Action sideEffect,
Action <Exception> exceptionHandler = null,
string debugName = null)
{
Reaction watcher = null;
watcher = new ReactionAtom(debugName, () =>
{
Exception exception = null;
try
{
if (!p())
{
return;
}
}
catch (Exception e)
{
exception = e;
}
if (exception != null && exceptionHandler == null)
{
Debug.LogException(exception);
return;
}
using (NoWatch)
{
if (exception != null)
{
exceptionHandler(exception);
}
else
{
sideEffect();
}
// ReSharper disable once AccessToModifiedClosure
watcher?.Deactivate();
watcher = null;
}
});
watcher.Activate();
return(watcher);
}
/// <summary>
/// Creates an reaction that observes and runs the given predicate function
/// until it returns true. Once that happens, the returned task is completed
/// and the reaction is deactivated.<br/>
/// <br/>
/// The task will fail if the predicate throws an exception.
/// </summary>
/// <param name="p">An observed predicate function.</param>
/// <param name="cancellationToken">Token for reaction cancellation.</param>
/// <param name="debugName">Debug name for this reaction.</param>
/// <returns>Task that completes when the predicate returns true or predicate function throws exception.</returns>
/// <example>
///
/// var counter = Atom.Value(1);
///
/// await Atom.When(() => counter.Value == 10);
/// Debug.Log("Counter value equals 10");
///
/// </example>
public static Task When(
Func <bool> p,
CancellationToken cancellationToken = default,
string debugName = null)
{
var taskCompletionSource = new TaskCompletionSource <object>();
Reaction watcher = null;
CancellationTokenRegistration?cancellationTokenRegistration = null;
void Dispose()
{
taskCompletionSource.TrySetCanceled();
// ReSharper disable once AccessToModifiedClosure
cancellationTokenRegistration?.Dispose();
// ReSharper disable once AccessToModifiedClosure
watcher?.Deactivate();
watcher = null;
}
watcher = new ReactionAtom(debugName, () =>
{
Exception exception = null;
try
{
if (!p())
{
return;
}
}
catch (Exception e)
{
exception = e;
}
using (NoWatch)
{
if (exception != null)
{
taskCompletionSource.TrySetException(exception);
}
else
{
taskCompletionSource.TrySetResult(null);
}
Dispose();
}
});
if (cancellationToken.IsCancellationRequested)
{
Dispose();
}
else
{
watcher.Activate();
if (cancellationToken.CanBeCanceled)
{
cancellationTokenRegistration = cancellationToken.Register(Dispose, true);
}
}
return(taskCompletionSource.Task);
}