多线程交替输出字符串（2）

与上一篇逻辑类似，这里采用同样的生产者消费者模式

创建线程使用了BlockOperation封装操作，使用OperationQueue作为并发队列

代码如下：

import Foundation
var run: Bool = true
/// 将字符转成UInt8
func charToInt(chr: Character) -> UInt8? {
    return chr.asciiValue
}
/// 将Uint8转成字符
func intToChr(asciiValue: UInt8) -> Character? {
    return Character(UnicodeScalar(asciiValue))
}
/// 组
let group = DispatchGroup()
group.enter()
let queue = OperationQueue()
queue.maxConcurrentOperationCount = 2
guard var start1: UInt8 = charToInt(chr: Character("A")) else {
    exit(-1)
}
let semaphore1 = DispatchSemaphore(value: 1)
let semaphore2 = DispatchSemaphore(value: 0)

let op1 = BlockOperation(block: {
    while run {
        sleep(1)
        semaphore1.wait()
        let first = (start1 - 65) % 26 + 65
        start1 = start1 + 1
        let second = (start1 - 65) % 26 + 65
        start1 = start1 + 1
        print("(intToChr(asciiValue: first)!), (intToChr(asciiValue: second)!)")
        semaphore2.signal()
    }
    group.leave()
})
var start2 = 0
let op2 = BlockOperation(block: {
    while run {
        sleep(1)
        semaphore2.wait()
        print("(start2 % 10)")
        start2 = start2 + 1
        semaphore1.signal()
    }
    group.leave()
})
queue.addOperation(op1)
queue.addOperation(op2)
group.wait()