Swift 后台执行代码封装库 Async

Swift 后台执行代码封装库 Async。

Swift 中写GDC(Grand Central Dispatch)类似这样的：

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), {
    print("This is run on the background queue")

    dispatch_async(dispatch_get_main_queue(), {
        print("This is run on the main queue, after the previous block")
    })
})

Async.background {
    print("This is run on the background queue")
}.main {
    print("This is run on the main queue, after the previous block")
}

Async.main {}
Async.userInteractive {}
Async.userInitiated {}
Async.utility {}
Async.background {}

Async.userInitiated {
    // 1
}.main {
    // 2
}.background {
    // 3
}.main {
    // 4
}