使函数只能从一个 class 调用

Question

我有一个 class LoggingManager 和一个协议 LoggingHandler，只有一个方法 send(LoggingEvent)。
LoggingManager 保留 LoggingHandler 的列表。
我希望 LoggingManager 成为允许从 LoggingHandler 和使用该协议的 classes 调用 send(LoggingEvent) 的 only class应该实现 send(LoggingEvent) 方法。

我尝试将 LoggingHandler 和 LoggingManager 放入同一个文件并将 send(LoggingEvent) 标记为 fileprivate。但是，它在协议中是不允许的。

有没有办法让它起作用？

LoggingManager.swift

import Foundation

public struct LoggingEvent {
    var eventName: String
    var eventParams: [String: Any]

    public init(_ name: String, _ eventParams: [String: Any]) {
        self.eventName = name
        self.eventParams = eventParams
    }

    public init(_ name: String) {
        self.eventName = name
        eventParams = [String: Any]()
    }

    mutating public func addParameter(_ eventName: String, _ eventValue: Any) {
        self.eventParams[eventName] = eventValue
    }
}

public protocol LoggingHandler {
    func logEvent(_ event: LoggingEvent) ///<--- Only LoggingManager should call this function, but classes implementing this should override it
}

public class LoggingManager {
    private var loggingHandlers: [LoggingHandler]
    static let shared = LoggingManager()

    private init() {
        loggingHandlers = []
    }

    public func registerLoggingHandler(_ loggingHandler: LoggingHandler) {
        loggingHandlers.append(loggingHandler)
    }

    public func logEvent(_ event: LoggingEvent) {
        for handler in loggingHandlers {
            handler.logEvent(event)
        }
    }
}

FirebaseLogger.swift

class FirebaseLogger: LoggingHandler {
    var firebaseApp: FirebaseApp?

    public init() {
        FirebaseApp.configure()
        firebaseApp = FirebaseApp.app()
    }

    func logEvent(_ event: LoggingEvent) {
        Analytics.logEvent(event.eventName, parameters: event.eventParams)
    }
}

LogLoggingHandler.swift（仅打印到控制台）

public class LogLoggingHandler: LoggingHandler {
    public func logEvent(_ event: LoggingEvent) {
        let name = event.eventName
        let description = event.eventParams.description
        print("LogEvent: \(name) \(description)")

    }
}

Answer 1

这不是最好的解决方案，但这是一个想法。在您的第一个文件中，您可以定义这些类型：

struct LoggingSecurity {
    fileprivate init() {}
}

class LoggingManager {
    private let handlers: [LoggingHandler]
    private let security: LoggingSecurity

    init(handlers: [LoggingHandler]) {
        self.handlers = handlers
        self.security = .init()
    }

    func broadcast(event: LoggingEvent) {
        handlers.forEach { handler in
            handler.send(
                event: event,
                securedBy: security
            )
        }
    }
}

由于 LoggingSecurity.init 方法被标记为 fileprivate 唯一可以实例化 LoggingSecurity 的 class 是 LoggingManager.

然后在您的其他文件中您可以定义这些类型：

struct LoggingEvent {
    let data: String
}

protocol LoggingHandler {
    func send(event: LoggingEvent, securedBy security: LoggingSecurity)
}

class PrintLoggingHandler: LoggingHandler {
    func send(event: LoggingEvent, securedBy security: LoggingSecurity) {
        print("LOG: \(event.data)")
    }
}

使函数只能从一个 class 调用

Make function only callable from one class

swift

swift-protocols