Question

有没有办法可以从我的闭包中返回shouldPerformSegueWithIdentifier方法的值？或者我应该采取不同的方式吗？

override func shouldPerformSegueWithIdentifier(identifier: String?, sender: AnyObject?) -> Bool {

    getDataFromSomewhere() { succeeded, data in
        if succeeded {
            // Should return true here            
        } else {
            self.errorAlert("Error", message: "Can't get data...")
            // Should return false here
        }
    }

}

Answer 1

您无法从放置shouldPerformSegueWithIdentifier:sender:的位置返回// Should return true here。你需要做这样的事情：

override func shouldPerformSegueWithIdentifier(identifier: String?, sender: AnyObject?) -> Bool {
    var returnValue: Bool = false

    getDataFromSomewhere() { succeeded, data in
        if succeeded {
            returnValue = true
        } else {
            self.errorAlert("Error", message: "Can't get data...")
            returnValue = false
        }
    }

    return returnValue
}

请注意，这仅在getDataFromSomewhere在getDataFromSomewhere返回之前执行闭包时才有效。如果getDataFromSomewhere存储闭包，并安排稍后调用它（例如，在异步网络请求之后），那么这将不起作用。它只会使shouldPerformSegueWithIdentifier:sender:返回您用于初始化returnValue的值。

Answer 2

您是否反对使用prepareforsegue和unwind segue？

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    if segue.identifier == "fuelButtonUnhide"{

        if let vc = segue.destinationViewController as? DateViewController {

            vc.fuelHidden = false
        }
    } 
}

@IBAction func unwindDateViewToAddFuel(segue: UIStoryboardSegue){
    //Change any data from the date view here
    println("Hit done from date view")
}

您可以在prepareforsegue中传递数据并在展开操作中检索数据。

Swift中关闭方法的返回值

2 个答案: