ReactiveCocoa5.0 &ReactiveSwift &Reactive.Swift (Base)理解

源码

/// Describes a provider of reactive extensions.////// - note: `ReactiveExtensionsProvider` does not indicate whether a type is///         reactive. It is intended for extensions to types that are not owned///         by the module in order to avoid name collisions and return type///         ambiguities.public protocol ReactiveExtensionsProvider: class {}extension ReactiveExtensionsProvider {    /// A proxy which hosts reactive extensions for `self`.    public var reactive: Reactive<Self> {        return Reactive(self)    }    /// A proxy which hosts static reactive extensions for the type of `self`.    public static var reactive: Reactive<Self>.Type {        return Reactive<Self>.self    }}/// A proxy which hosts reactive extensions of `Base`.public struct Reactive<Base> {    /// The `Base` instance the extensions would be invoked with.    public let base: Base    /// Construct a proxy    ///    /// - parameters:    ///   - base: The object to be proxied.    fileprivate init(_ base: Base) {        self.base = base    }}

对Base自己的理解 不知道对不对

---

上面的代码简短 但是功能强大 所以拿出来分析一下
先来看看struct
定义的一个结构体 但是类型是Base 你会发现Swift里是没有这个类型的 ,其实奥秘就在Reactive中的那个

* 不同之处在于这个范型结构体后面跟着的占位类型名称 Base 并且是用<>包围修饰的 ，这个<> 告诉Swift 那个Base 是 Reactive结构体内的一个占位类型名 因此 Swift是不会去查找这个名为Base的实际类型 只有在初始化Reactive的时候，才能根据所传入的实际类型决定 Base 所代表的类型*