Question

在我下面显示的swift 3程序中，我想在计算的初始化程序中访问计算变量'darkColor'。但swift 3编译器给我一个错误：实例成员'darkColor'不能用于'LoginViewController'类型

import UIKit

class LoginViewController: BaseViewController, UITextFieldDelegate {

    // FIXME: - computed variables
    private var darkColor: UIColor {
        return UIColor(hex: 0x0083C5, alpha: 1)
    }

    // FIXME: - create views / computed initializers
    lazy var textEmail: UITextField = {
        let textField = UITextField()
        textField.placeholder = "Email"
        textField.font = UIFont.systemFont(ofSize: 18, weight: UIFontWeightSemibold)
        textField.textColor = darkColor     // here I'm getting error that "instance member 'darkColor' cannot be used on type 'LoginViewController'"
        textField.keyboardType = .emailAddress
        textField.autocorrectionType = .no
        textField.translatesAutoresizingMaskIntoConstraints = false
        textField.delegate = self
        return textField
    }()

    let emailUnderline: UIView = {
        let view = UIView()
        view.backgroundColor = darkColor     // here I'm getting error that "instance member 'darkColor' cannot be used on type 'LoginViewController'"
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    // FIXME: - life cycle
    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.white
    }
}

Answer 1

在计算变量init

期间，几乎没有可能的方法

对self.darkColor变量使用lazy，因为它只会在访问时创建（在初始化类时无法访问self）
更改为类变量，但这会影响LoginViewController
将let darkColor {...}移到课程范围之外会使其成为全局常量

Answer 2

感谢@ Tj3n给我提示。我找到了4个解决这个问题的方法。其中3人来自Tj3n。

解决方案1 - 为常量使用不同的类

解决方案2 - 使用class var而不是var

int num = 1;
object arg;
bool flag = arg = num as object != null;
if (!flag)
{
    arg = null;
}
Console.WriteLine("This should NOT be in scope:" + arg);

解决方案3 - 使用static let而不是var

class var darkColor: UIColor {
    return UIColor(hex: 0x0083C5, alpha: 1)
}

解决方案4 - 对于惰性var类型的计算变量使用self.darkColor。例如，

static let darkColor: UIColor = {
    return UIColor(hex: 0x0083C5, alpha: 1)
}()

如何在swift 3中访问计算初始化程序内的计算变量？

2 个答案: