ios - 推送 UIViewController 时实例成员不能用于类型

Question

我正在以编程方式设置 ViewController(无 Storyboard)。

我想将数据传递给下一个 VC，虽然我知道如何使用 segue 和 Storyboard来做到这一点，但我无法弄清楚如何纯粹以编程方式做到这一点。

我收到错误“实例成员不能用于类型...”

// Create Next View Controller Variable

let nextViewController = CarbonCalculatorResultsViewController()

// Pass data to next view controller.  There is already a variable in that file: var userInformation: UserInformation?

CarbonCalculatorResultsViewController.userInformation = userInformation

// Push next View Controller
self.navigationController?.pushViewController(nextViewController, animated: true)

在传递数据之前是否需要实例化下一个VC？这就是this answer seems to talk about但我没有 Storyboard。谢谢!

Answer 1

第 1 步:设置目标类(class)

在 CarbonCalculatorResultsViewController 类中，声明一个 var 来接收数据，如下所示:

class CarbonCalculatorResultsViewController: UIViewController {
    var foo: String? {
        didSet {
            // What you'd like to do with the data received
            print(foo ?? "")
        }
    }

    ovevride func viewDidLoad() {
       //
    }
}

第 2 步:在源类中准备数据

let nextViewController = CarbonCalculatorResultsViewController()
// You have access of the variable in CarbonCalculatorResultsViewController
nextViewController.foo = <data_you_want_to_pass>

// Push next View Controller
self.navigationController?.pushViewController(nextViewController, animated: true)

然后，每次 CarbonCalculatorResultsViewController 激活时，foo 的 didSet{} 都会被调用。