if语句的预期声明

Question

我想要一行代码，每当用户将位置切换到卡萨布兰卡时，它们都会更改情节提要，但由于某些原因，我编写的代码不正确。怎么了？

导入UIKit

ViewController类：UIViewController，UIPickerViewDataSource，UIPickerViewDelegate {

@IBOutlet weak var locationlabel: UILabel!
@IBOutlet weak var locationpicker: UIPickerView!

let locations = ["Select your location", "Casablanca"]

func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return locations[row]
}

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return locations.count
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    locationlabel.text = locations[row]
}


if (locationlabel.text == "Casablanca") {
let storyboard = UIStoryboard(name: "NextBoard1", bundle: nil)
let vc = storyboard.instantiateInitialViewController()!
present(vc, animated: true, completion: nil)
}




override func viewDidLoad() {
    super.viewDidLoad()


}

}

Answer 1

您需要以编程方式更改情节提要，而不仅仅是执行顺序。

假设您有另一个名为“ NextBoard1”的情节提要，并且此情节提要的开头为UIViewController，则可以尝试以下操作：

if (locationlabel.text == "Casablanca") {
     let storyboard = UIStoryboard(name: "NextBoard1", bundle: nil)
     let vc = storyboard.instantiateInitialViewController()!
     present(vc, animated: true, completion: nil)
}

编辑-示例代码

考虑此设置：

Main.storyboard具有一个具有自定义类ViewController的视图控制器，该类具有一个标签和一个选择器：

NextBoard1.storyboard具有一个初始视图控制器：

ViewController.swift

import UIKit

class ViewController: UIViewController,UIPickerViewDataSource, UIPickerViewDelegate {

    @IBOutlet weak var locationlabel: UILabel!
    @IBOutlet weak var locationpicker: UIPickerView!

    let locations = ["Select your location", "Casablanca"]

    override func viewDidLoad() {
        super.viewDidLoad()
        locationpicker.delegate = self
        locationpicker.dataSource = self
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return locations[row]
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return locations.count
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        locationlabel.text = locations[row]

        if (locationlabel.text == "Casablanca") {
            let storyboard = UIStoryboard(name: "NextBoard1", bundle: nil)
            let vc = storyboard.instantiateInitialViewController()!
            present(vc, animated: true, completion: nil)
        }
    }

}

输出