GCDCancelableDelayCall

GCDCancelableDelayCall.swift

import Foundation

class GCDDelayTask: NSObject {

    typealias DelayTask = (_ cancel: Bool) -> Void

    var pendingTask: DelayTask?

    /// 延时执行
    func delay(time: TimeInterval, task: @escaping () -> ()) {

        func dispatch_later(block: @escaping () -> ()) {
            DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + time, execute: block)
        }

        var closure: (() -> ())? = task
        var result: DelayTask?

        let delayedClosure: DelayTask = {
            cancel in
            if let internalClosure = closure {
                if cancel == false {
                    DispatchQueue.main.async(execute: internalClosure)
                }
            }
            closure = nil
            result = nil
        }

        result = delayedClosure

        dispatch_later {
            if let delayedClosure = result {
                delayedClosure(false)
            }
        }

        pendingTask = result
    }

    /// 取消待执行的任务
    func cancel() {
        pendingTask?(true)
    }

    /// 有待执行的任务
    func hasTask() -> Bool {
        return nil != pendingTask
    }
}