Accessors
存取方法
All instance variables are private in Objective-C by default, so you should use accessors to get and set values in most cases. There are two syntaxes. This is the traditional 1.x syntax:
OC中所有的实例变量默认是私有的，所以多数情况下你应该使用访问器来获得和设置实例变量的值。访问器有两种语法。下面说的是传统的1.x版本：
[photo
setCaption:@"Day at the Beach"];
output = [photo
caption];
The code on the second line is not reading the instance variable directly. It‘s actually calling a method named caption. In most cases, you don‘t add the "get" prefix to
getters in Objective-C.
上面的第二行代码不是直接读取实例变量值，实际上是调用了名叫caption的方法。多数情况下，你不要在OC的取值方法中添加"get"前缀。
Whenever you see code inside square brackets, you are sending a message to an object or a class.
每当你看到中括弧中得代码时，你正在给一个类或实例对象发送消息。
Dot Syntax
点语法
The dot syntax for getters and setters is new in Objective-C 2.0, which is part of Mac OS X 10.5:
存取方法的点语法是在OC 2.0版中作为Mac
OS X 10.5的一部分新加入的。
photo.caption = @"Day at the Beach";
output = photo.caption;
You can use either style, but choose only one for each project. The dot syntax should only be used setters and getters, not for general purpose methods.
你可以使用以上两种方式，但一个项目只能选用一种方式。点语法不适用于普通用意的方法，只能用作设值和取值方法，也就是存取方法。
原文：learn_objective_C part
2
【OC语法快览】二、存取方法