RxSwift | 万物皆 rx 的原因

因为 RxSwift 给 NSObject 扩展了一个协议 ReactiveCompatible:

import class Foundation.NSObject

/// Extend NSObject with `rx` proxy.
extension NSObject: ReactiveCompatible { }

在 ReactiveCompatible 协议里，添加了属性 rx：

/// A type that has reactive extensions.
public protocol ReactiveCompatible {
    /// Extended type
    associatedtype ReactiveBase

    @available(*, deprecated, renamed: "ReactiveBase")
    typealias CompatibleType = ReactiveBase

    /// Reactive extensions.
    static var rx: Reactive&lt;ReactiveBase&gt;.Type { get set }

    /// Reactive extensions.
    var rx: Reactive<ReactiveBase> { get set }
}

extension ReactiveCompatible {
    /// Reactive extensions.
    public static var rx: Reactive<Self>.Type {
        get {
            return Reactive<Self>.self
        }
        // swiftlint:disable:next unused_setter_value
        set {
            // this enables using Reactive to "mutate" base type
        }
    }

    /// Reactive extensions.
    public var rx: Reactive<Self> {
        get {
            return Reactive(self)
        }
        // swiftlint:disable:next unused_setter_value
        set {
            // this enables using Reactive to "mutate" base object
        }
    }
}