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（无故事板）。

我想将数据传递给下一个 VC，虽然我知道如何使用 segue 和情节提要来做到这一点，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 "Instance Member Cannot Be Used on Type..."

// 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)

是否需要实例化下一个VC才能传递数据？就是这样但我没有故事板。谢谢！

Answer 1

您应该在 Object 上传递变量，而不是在 Class

上传递变量

替换：CarbonCalculatorResultsViewController.userInformation = userInformation

有： nextViewController.userInformation = userInformation

注：

CarbonCalculatorResultsViewController 就是 Class.

nextViewController 就是 Object.

您的完整代码应如下所示：

// 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?

nextViewController.userInformation = userInformation

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

Answer 2

当前示例代码（以上）正在为静态变量（由 CarbonCalculatorResultsViewController.Type 所有。

设置一个值

我认为您要执行的是以下内容：

// 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?

nextViewController.userInformation = userInformation

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

此示例代码正在为类型 nextViewController 上的实例变量 userInformation 设置一个值。

Answer 3

第 1 步：设置目的地 class

在 CarbonCalculatorResultsViewController class 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：在源中准备数据 class

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 活跃时，都会调用 foo 的 didSet{}。

推送 UIViewController 时实例成员不能用于类型

Instance Member Cannot Be Used on Type when pushing UIViewController

uinavigationcontroller

ios

programmatically-created

swift

swift4