仿 Android HandlerThread 的 Message Queue(一小部分功能)

MessageQueue.swift

import Foundation

public class MessageQueue {
    
    public typealias Message = Void -> Void
    
    private var exitFlag = false
    
    private var messageQueue:[Message] = []
    private var loopInterval:Double
    
    public let dispatchQueue:dispatch_queue_t
    
    public init? (name:String,loopInterval:Double = 0.5) {
        guard let _dispatchQueue = dispatch_queue_create(name, DISPATCH_QUEUE_SERIAL) else {
            return nil
        }
        
        self.loopInterval = loopInterval
        self.dispatchQueue = _dispatchQueue
        self.loopAfterInBackground() {
            self.loop()
        }
    }
    
    private func loop() {
        if exitFlag {
            return
        }
        
        if let msg = messageQueue.first {
            messageQueue.removeFirst(1)
            handleMessage(msg)
        }
        
        loopAfterInBackground() {
            self.loop()
        }
    }
    
    private func loopAfterInBackground(block:dispatch_block_t) {
        let queue = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
        let nanoSeconds = Int64(loopInterval * Double(NSEC_PER_SEC))
        let time = dispatch_time(DISPATCH_TIME_NOW, nanoSeconds)
        let _block = dispatch_block_create(DISPATCH_BLOCK_INHERIT_QOS_CLASS, block)
        dispatch_after(time, queue, _block)
    }
    
    private func handleMessage(msg:Message) {
        dispatch_sync(dispatchQueue) {
            msg()
        }
    }
    
    public func sendMessage(msg:Message) {
        messageQueue.append(msg)
    }
    
    public func clear() {
        messageQueue = []
    }
    
    public func exit() {
        exitFlag = true
    }
    
}