Author: Cockroach Bully
Link: https://www.zhihu.com/question/391094769/answer/3101596697
Source: Zhihu
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Unity is a powerful game development engine that provides many handy tools and features to simplify the game development process. One of the very important functions is Coroutine . A coroutine is a special function that allows us to implement asynchronous operations in a program without using multithreading or callback functions . This article will explain in detail what Unity's coroutines are all about.
- What is a coroutine?
A coroutine is a special kind of function that can pause and resume execution while running. It is similar to threads, but unlike threads, coroutines are scheduled by the program itself, not by the operating system . This means we can perform some time-consuming operations in coroutines without blocking the main thread .
- How to use coroutines?
In Unity, we can use C# language to write coroutines. To create a coroutine, we need to use the keyword yield and add the keyword IEnumerator in front of the function. For example:
IEnumerator MyCoroutine()
{
// 协程的执行内容
yield return null;
// 继续执行协程的内容
}In the coroutine, we can use the yield keyword to suspend the execution of the coroutine and resume it when needed. The yield keyword can be followed by some special instructions, for example, yield return null means to pause for one frame, and yield return new WaitForSeconds(1) means to pause for 1 second.
- The use of coroutines
Coroutines have many uses in game development, here are some common application scenarios:
a. Delayed operation : coroutines can be used to implement some delayed execution operations. For example, we can use coroutines to achieve the effect of playing an animation after a delay of a few seconds.
b. Animation control: Coroutines can be used to control the animation of objects. For example, we can use coroutines to achieve a smooth movement effect, moving a small distance every frame to achieve animation effects.
c. Asynchronous loading : Coroutines can be used to load resources asynchronously. For example, we can use coroutines to load large texture or audio files without blocking the main thread.
d. Game flow control: coroutines can be used to control the flow of the game. For example, we can use coroutines to achieve a countdown effect, or to achieve a series of tasks in the game.
- Notes on coroutines
When using coroutines, there are some caveats to be aware of:
a. Coroutines can only be used in derived classes of MonoBehaviour . This is because coroutines need to be scheduled through Unity's message loop.
b. Coroutines cannot use methods with out or ref parameters . This is because the execution of the coroutine may be paused and resumed, and these parameters may change during the pause and resume process.
c. The execution order of coroutines is undefined. Since the coroutine is scheduled by the program itself, the order and times of execution of the coroutine cannot be guaranteed.
d. The coroutine can stop execution through StopCoroutine(). If you don't manually stop the coroutine, it will continue to execute until the game object is destroyed.