ios - 如何在 swift 3.0 中返回 void @escaping 闭包？

Question

我是 swift 3.0 的新手，我在一个小代码片段中遇到了问题，当我按照所附的屏幕截图将 @escaping 闭包分配给 nil 时会抛出错误:

这是我的代码...

func delay(_ time:TimeInterval, closure: @escaping ()-> ()) -> dispatch_cancelable_closure? 
{

    func dispatch_later(_ clsr:@escaping ()->Void) {
        DispatchQueue.main.asyncAfter(
            deadline: DispatchTime.now() + Double(Int64(time * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC), execute: clsr)
    }
    var closure : ()->()? = closure
    var cancelableClosure:dispatch_cancelable_closure?
    let delayedClosure:dispatch_cancelable_closure = { cancel in

        if closure != nil {
            if (cancel == false) {
                DispatchQueue.main.async(execute: closure as! @convention(block) () -> Void);
            }
        }

        closure = nil
        cancelableClosure = nil

    }
    cancelableClosure = delayedClosure
    dispatch_later {
        if let delayedClosure = cancelableClosure {
            delayedClosure(false)
        }
    }
    return cancelableClosure;
}

谁能帮我解决这个问题。
提前致谢。

Answer 1

似乎您的问题更多的是可选闭包类型而不是 @escaping .

尝试改变这一行:

var closure : ()->()? = closure

到:

var closure : (()->())? = closure

()->()?表示返回 ()? 的非可选闭包(又名 Optional<Void> )，这可能不是您想要的。