异步执行任务的简单封装 -> Swift版

 

func async<T, N>(_ delta: Double, param: T, task: @escaping (_ value: T) -> N, callFunc: @escaping (_ result: N) -> ()) {
    func doTaskThenCallback() {
        let t = task(param)
        DispatchQueue.main.async(execute: {
            callFunc(t)
        })
    }

    if delta > 0.0 {
        DispatchQueue.global().asyncAfter(
            deadline: DispatchTime.now() + Double(Int64(delta * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC)) {
                doTaskThenCallback()
        }
    } else {
        DispatchQueue.global().async {
            doTaskThenCallback()
        }
    }
}

　　

简单的使用小例子：

　　func asyncFetchImageBin(completion: ((Data?) -> Void)?) {
        if let bin = imageBin {
            completion?(bin)
        } else {
            // get bin data from cache file
            async(0.0, param: cacheFilePath, task: { (path) -> Data? in
                guard let bin = try? Data.read(from: path) else { return nil }
                return bin
            }, callFunc: { (bin) in
                completion?(bin)
            })
        }
    }