协程有什么好处？

发布于 2024-12-01 17:31:42 字数 240 浏览 0 评论 0原文

我一直在学习一些用于游戏开发的lua。我听说过其他语言中的协程，但真正接触到它们是在 lua 中。我只是不太明白它们有多有用，我听到很多人谈论它如何成为一种执行多线程操作的方法，但它们不是按顺序运行的吗？那么按顺序运行的正常函数会有什么好处呢？我只是不明白它们与函数有什么不同，除了它们可以暂停并让另一个函数运行一秒钟。似乎用例场景对我来说不会那么大。

有人愿意解释一下为什么有人会从中受益吗？

特别是从游戏编程角度的洞察力会很好^^

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那片花海 2024-12-08 17:31:42

好吧，从游戏开发的角度来思考。

假设您正在制作过场动画或教程。无论哪种方式，您所拥有的都是发送到一定数量的实体的有序命令序列。一个实体移动到一个位置，与一个人交谈，然后走到其他地方。等等。有些命令只有在其他命令完成后才能启动。

现在回顾一下你的游戏是如何运作的。每一帧，它都必须处理人工智能、碰撞测试、动画、渲染和声音，以及其他可能的东西。你只能思考每一帧。那么，如何将这种代码放入必须等待某个操作完成才能执行下一个操作的地方呢？

如果你用 C++ 构建一个系统，你所拥有的将会是在人工智能之前运行的东西。它将有一系列命令要处理。其中一些命令是即时的，例如“告诉实体 X 到这里”或“在此处生成实体 Y”。其他人则必须等待，例如“告诉实体 Z 到这里，并且在它到达这里之前不要处理任何命令。”命令处理器必须在每一帧被调用，并且它必须理解复杂的条件，例如“实体位于位置”等等。

在 Lua 中，它看起来像这样：

local entityX = game:GetEntity("entityX");
entityX:GoToLocation(locX);
local entityY = game:SpawnEntity("entityY", locY);
local entityZ = game:GetEntity("entityZ");
entityZ:GoToLocation(locZ);
do
  coroutine.yield();
until (entityZ:isAtLocation(locZ));
return;

在 C++ 大小上，您将每帧恢复此脚本一次，直到完成。一旦它返回，您就知道过场动画已经结束，因此您可以将控制权返回给用户。

看看 Lua 逻辑多么简单。它完全按照它所说的那样做。它很清楚、显而易见，因此很难出错。

协程的强大之处在于能够部分完成某些任务，等待条件成立，然后继续执行下一个任务。

OK, think in terms of game development.

Let's say you're doing a cutscene or perhaps a tutorial. Either way, what you have are an ordered sequence of commands sent to some number of entities. An entity moves to a location, talks to a guy, then walks elsewhere. And so forth. Some commands cannot start until others have finished.

Now look back at how your game works. Every frame, it must process AI, collision tests, animation, rendering, and sound, among possibly other things. You can only think every frame. So how do you put this kind of code in, where you have to wait for some action to complete before doing the next one?

If you built a system in C++, what you would have is something that ran before the AI. It would have a sequence of commands to process. Some of those commands would be instantaneous, like "tell entity X to go here" or "spawn entity Y here." Others would have to wait, such as "tell entity Z to go here and don't process anymore commands until it has gone here." The command processor would have to be called every frame, and it would have to understand complex conditions like "entity is at location" and so forth.

In Lua, it would look like this:

local entityX = game:GetEntity("entityX");
entityX:GoToLocation(locX);
local entityY = game:SpawnEntity("entityY", locY);
local entityZ = game:GetEntity("entityZ");
entityZ:GoToLocation(locZ);
do
  coroutine.yield();
until (entityZ:isAtLocation(locZ));
return;

On the C++ size, you would resume this script once per frame until it is done. Once it returns, you know that the cutscene is over, so you can return control to the user.

Look at how simple that Lua logic is. It does exactly what it says it does. It's clear, obvious, and therefore very difficult to get wrong.

The power of coroutines is in being able to partially accomplish some task, wait for a condition to become true, then move on to the next task.

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