CustomYieldInstruction

Description

Base class for custom yield instructions to suspend coroutines.

CustomYieldInstruction lets you implement custom yield instructions to suspend coroutine execution until an event happens. Under the hood, custom yield instruction is just another running coroutine. To implement it, inherit from CustomYieldInstruction class and override keepWaiting property. To keep coroutine suspended return true. To let coroutine proceed with execution return false. keepWaiting property is queried each frame after MonoBehaviour.Update and before MonoBehaviour.LateUpdate.

This class requires Unity 5.3 or later.

no example available in JavaScript

using UnityEngine;

// Implementation of WaitWhile yield instruction. This can be later used as:
// yield return new WaitWhile(() => Princess.isInCastle);
class WaitWhile: CustomYieldInstruction {
	Func<bool> m_Predicate;

	public override bool keepWaiting { get { return m_Predicate(); } }

	public WaitWhile(Func<bool> predicate) { m_Predicate = predicate; }
}

To have more control and implement more complex yield instructions you can inherit directly from System.Collections.IEnumerator class. In this case, implement MoveNext() method the same way you would implement keepWaiting property. Additionaly to that, you can also return an object in Current property, that will be processed by Unity's coroutine scheduler after executing MoveNext() method. So for example if Current returned another object inheriting from IEnumerator, then current enumerator would be suspended until the returned one has completed.

no example available in JavaScript

// Same WaitWhile implemented by inheriting from IEnumerator.
class WaitWhile: IEnumerator {
	Func<bool> m_Predicate;

	public object Current { get { return null; } }

	public bool MoveNext() { return m_Predicate(); }

	public void Reset() {}

	public WaitWhile(Func<bool> predicate) { m_Predicate = predicate; }
}

Variables