ios - 在我想要的时候执行 segue

Question

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

这是我的:

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。但我不知道热用它。有什么建议吗？

Answer 1

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

P.S:Swift 3 代码(我假设这就是您想要的)。

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
        }
    }

希望这对您有所帮助。