问题描述
在下面的示例中，有人可以解释为什么在类型别名 Generator之后有一个：吗？是说 Generator符合 GeneratorType吗？我很困惑，因为当我阅读Swift文档时，它仅在别名之后描述一个 =符号。
Can someone explain why there is a ":" after the typealias "Generator" in the example below? Is it saying that "Generator" is conforming to "GeneratorType"? I am confused because when I read the Swift documentation, it only describes an "=" sign after an alias name.
protocol SequenceType : _Sequence_Type {
typealias Generator : GeneratorType
func generate() -> Generator
}
推荐答案
在协议中， typealias 声明一个。符合该协议的类和结构必须具有 typealias 指令，该指令将类型声明为具体的东西。
In a protocol, typealias declares an associated type. Classes and structures that conform to this protocol must have a typealias directive that declares the type to something concrete.
是，这意味着 Generator 在 SequenceType GeneratorType c $ c>协议。
Yes, it means that Generator must conform to GeneratorType in any implementation of the SequenceType protocol.
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