问题描述
东西我看到脂肪酶这样定义变量：
Something I see ppl define the variable like this:
b2World *_world;
b2Body *_body;
CCSprite *_ball;
而不是
b2World *world;
b2Body *body;
CCSprite *ball;
我熟悉的第二个，但不是第一个。所以，我查了维基百科有关命名约定：
I familiar with the second one, but not the first one. So, I checked the Wikipedia about naming convention:
名称以双下划线
或下划线和一个大写字母
被保留用于执行
（编译器，标准库）和
不应该被使用（例如__reserved或
_Reserved）。
那么，是什么特别的含义是开始_？
So, is that any special meaning which is start with "_"?
我看到它使用_开始的code是在这里：
The code I saw which using "_" to begin is here:
推荐答案
有一些Objective-C的开发商preFIX实例变量以下划线之间长期存在的约定。它可以在几个方面是有帮助的：一，它可以更容易被发现在.m文件的实例变量;二，它解除不得不想出有创意的名字方法的参数，以避免与实例变量的名称发生冲突的开发;三，正如其他人所指出的，这表明该实例变量是私有的，因此不应该在整个code威利愿意不愿意访问。
There's a long-standing convention among some Objective-C developers to prefix instance variables with an underscore. It can be helpful in several ways: one, it makes it easier to spot instance variables in a .m file; two, it relieves developers of having to come up with creative names for method parameters to avoid colliding with instance variable names; and three, as others have noted, it indicates that the instance variables are private, and therefore shouldn't be accessed willy nilly throughout the code.
其实，我要说直接避免超过存取（getter和setter）， -dealloc 和其他方法访问实例变量-init ... 。这并不是说你应该永远不会使用它们其他地方，但你应该直接在其他方法使用一个实例变量之前，至少可以给它一些思考。
In fact, I'd argue for avoiding accessing instance variables directly in methods other than accessors (getters and setters), -dealloc, and -init.... Not that you should never, ever use them anywhere else, but you should at least give it some thought before using an instance variable directly in other methods.
这篇关于目标C的命名约定/ C，先从＆QUOT; _＆QUOT;？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！