swift - Swift中 Unresolved 标识符错误？

我知道在Swift中，未解析的标识符通常是一个非常简单的修复方法，但无论如何，我仍然会遇到一些困难。我知道我没有声明我需要的实例或变量，但我不确定这样做的正确方式。这是我的代码：

import UIKit
import Foundation

func setButton(viewInfo:ChemistryViewInfo, inout button:UIButton, index:Int) {
let buttonInfo = viewInfo.buttons[0]
button.titleLabel?.text = buttonInfo.scale
button.backgroundColor = buttonInfo.color
}


class ChemistryMasterViewController: UIViewController {

    @IBOutlet weak var chemistryButton0: UIButton!
    @IBOutlet weak var chemistryButton1: UIButton!
    @IBOutlet weak var chemistryButton2: UIButton!
    @IBOutlet weak var chemistryButton3: UIButton!
    @IBOutlet weak var chemistryButton4: UIButton!
    @IBOutlet weak var chemistryButton5: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        if let viewInfo = viewInfo {
            setButton(viewInfo, button: &chemistryButton0, index: 0)
            setButton(viewInfo, button: &chemistryButton1, index: 1)
            setButton(viewInfo, button: &chemistryButton2, index: 2)
            setButton(viewInfo, button: &chemistryButton3, index: 3)
            setButton(viewInfo, button: &chemistryButton4, index: 4)
            setButton(viewInfo, button: &chemistryButton5, index: 5)
        }
}

}

还有。。。

import Foundation

import UIKit

let chemistryViewChoice = ["pH":
ChemistryViewInfo(
    text: "pH",
    description: "Most living things depend on proper pH level to sustain life.",
    buttons: [
        ChemistryButtonInfo(scale: "6.2", color: UIColor(red: 212, green: 142, blue: 69)),
        ChemistryButtonInfo(scale: "6.8", color: UIColor(red: 209, green: 122, blue: 31)),
        ChemistryButtonInfo(scale: "7.2", color: UIColor(red: 196, green:  80, blue:  9)),
        ChemistryButtonInfo(scale: "7.8", color: UIColor(red: 194, green:  74, blue: 58)),
        ChemistryButtonInfo(scale: "8.4", color: UIColor(red: 208, green:  48, blue: 75))]),
"Ammonia":
    ChemistryViewInfo(
        text: "Ammonia",
        description: "",

        buttons: [
            ChemistryButtonInfo(scale: "0.00", color: UIColor(red: 244, green: 235, blue: 130)),
            ChemistryButtonInfo(scale: "0.25", color: UIColor(red: 233, green: 233, blue: 156)),
            ChemistryButtonInfo(scale: "0.50", color: UIColor(red: 223, green: 238, blue: 141)),
            ChemistryButtonInfo(scale: "1.00", color: UIColor(red: 221, green: 236, blue: 210)),
            ChemistryButtonInfo(scale: "3.00", color: UIColor(red: 202, green: 227, blue: 191)),
            ChemistryButtonInfo(scale: "6.00", color: UIColor(red: 202, green: 216, blue: 173))])
]

最后：

import Foundation
import UIKit

struct ChemistryButtonInfo{
    let scale: String
    let color: UIColor
}

struct ChemistryViewInfo {

    let text: String
    let description: String
    let buttons: [ChemistryButtonInfo]
    }

    extension UIColor {
    convenience init(red:Int, green:Int, blue:Int) {
        self.init(
            red:   CGFloat(red)/255.0,
            green: CGFloat(green)/255.0,
            blue:  CGFloat(blue)/255.0,
            alpha: 1.0)
    }
}

错误出现在if-let语句的第二个viewInfo上。我想知道声明viewInfo的正确方法是什么。
任何建议、意见或回答都非常感谢。
提前谢谢。

最佳答案

假设您将在ChemistryMasterViewController类中声明viewInfo实例变量，则可以执行此操作。

var viewInfo:ChemistryViewInfo? //instance property declaration

    if let viewInfo = self.viewInfo  {
    ....
    ....
    }