当我想要的时候执行segues

Question

晚上，我的 VC 中有 2 场演出。但我只想在我的pickerView 有row.count > 0 时触发这些segues。

这就是我所拥有的：

Override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

if segue.identifier == "searchImages" {

    if pickerView.numberOfRows(inComponent: 0) > 0  {

        let controller = (segue.destination) as! WebViewController
        //replacing " " with "+" for google search queries
        let type: WebViewController.SearchType = .image
        let queryString = String(nameLabel.text!.characters.map {
                    $0 == " " ? "+" : $0
        })
        controller.searchType = type
        controller.queryString = queryString
        print("2")
        }

        }
        if segue.identifier == "searchWiki" {

        if pickerView.numberOfRows(inComponent: 0) > 0  {
            let controller = (segue.destination) as! WebViewController
            //replacing " " with "+" for google search queries
            let type: WebViewController.SearchType = .wiki
            let queryString = String(nameLabel.text!.characters.map {
                    $0 == " " ? "+" : $0
            })
            controller.searchType = type
            controller.queryString = queryString
        }
    }
}

我知道我应该使用：ShouldperformSomething。但我不知道热使用它。 有什么建议吗？

Answer 1

您应该实现shouldPerformSegue，而不是在您的prepareForSegue 方法中检查pickerView.numberOfRows(inComponent: 0) > 0。

P.S：Swift 3 代码（我认为这就是你想要的）。

override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
        return pickerView.numberOfRows(inComponent: 0) > 0
}

现在，prepareForSegue 方法应该类似于：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "searchImages" {
            let controller = (segue.destination) as! WebViewController
            //replacing " " with "+" for google search queries
            let type: WebViewController.SearchType = .image
            let queryString = String(nameLabel.text!.characters.map {
                $0 == " " ? "+" : $0
            })
            controller.searchType = type
            controller.queryString = queryString
            print("2")

        }

        if segue.identifier == "searchWiki" {
            let controller = (segue.destination) as! WebViewController
            //replacing " " with "+" for google search queries
            let type: WebViewController.SearchType = .wiki
            let queryString = String(nameLabel.text!.characters.map {
                $0 == " " ? "+" : $0
            })
            controller.searchType = type
        }
    }

希望这会有所帮助。

Answer 2

您不应该检查 UIStoryboardSegue 的 prepare 委托，而应该检查 shouldPerform：

override func shouldPerformSegueWithIdentifier(identifier: String!, sender: AnyObject!) -> Bool {
    return pickerView.numberOfRows(inComponent: 0) > 0
}