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协议章节中关于类属性和类方法的定义描述不达意，理解有困难 #222

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协议章节中关于类属性和类方法的定义描述不达意，理解有困难 #222

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Update 21_Protocols.md
zhousak Jun 18, 2014
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Update 21_Protocols.md
zhousak Jun 18, 2014
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5 changes: 2 additions & 3 deletions source/chapter2/21_Protocols.md
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Expand Up @@ -67,8 +67,7 @@ protocol SomeProtocol {
}
```

用类来实现协议时，使用`class`关键字来表示该属性为类成员；用结构体或枚举实现协议时，则使用`static`关键字来表示：

在协议中定义类属性 (type property)时使用`class`前缀关键字，即使在结构体或者枚举中类属性是要求使用`static`前缀关键字：
```swift
protocol AnotherProtocol {
class var someTypeProperty: Int { get set }
Expand Down Expand Up @@ -120,7 +119,7 @@ var ncc1701 = Starship(name: "Enterprise", prefix: "USS")
协议方法支持`变长参数(variadic parameter)`，不支持`默认参数(default parameter)`。

前置`class`关键字表示协议中的成员为`类成员`；当协议用于被`枚举`或`结构体`遵循时，则使用`static`关键字。如下所示：

像类属性的要求一样，协议中定义类方法时也总是使用`class`关键字，即使类方法在`枚举`或`结构体`中实现时要求使用`static`关键字
```swift
protocol SomeProtocol {
class func someTypeMethod()
Expand Down