为什么我不能将元素附加到结构？ [复制]

Question

这是我的代码：

import UIKit

struct StructName{
    var name: String?
    var specs: [Spec]?

    init(specs: [Spec]? = nil, name: String? = nil) {
        self.specs = specs
        self.name = name
    }

}

struct Spec{
    var name: String
    var title: String
    var content: String
    var display: Bool
}

class ViewController: UIViewController {
    var structNames: [StructName] = []
    var specs = [Spec]()

    override func viewDidLoad() {
        super.viewDidLoad()
            specs.append(Spec(name: "Name_1", title: "Title_1", content: "Content_1", display: false))
            structNames.append(StructName(name: "Name_3"))
            structNames.append(StructName(name: "Name_4"))
            structNames.append(StructName(name: "Name_1"))

            append()
            print(structNames)
    }


    func append(){
        for i in specs{
            let index = structNames.index { (structName) -> Bool in
                structName.name == i.name
            }
            print(structNames[index!].name)

            structNames[index!].specs?.append(Spec(name: "a", title: "a", content: "a", display: false))
        }
    }


}

为什么这不起作用？

        structNames[index!].specs?.append(Spec(name: "a", title: "a", content: "a", display: false))

它应该打印这个：

[test.Utility(utility_name: Optional("Name_3"), specs: nil), test.Utility(utility_name: Optional("Name_4"), specs: nil), test.Utility(utility_name: Optional("Name_1" "), specs: "SPEC I APPENDED")]

您可能理解，我想将给定的 Spec 附加到特定索引。

Answer 1

您永远不会将每个StructName 的specs 属性初始化为nil 以外的任何值。因此，当您引用 structNames[index!].specs 时，specs 是 nil 并且可选链接跳过对 append 的调用。

一种解决方案是将specs 初始化为一个空数组，而不是nil。

struct StructName{
    var name: String?
    var specs: [Spec]

    init(specs: [Spec] = [], name: String? = nil) {
        self.specs = specs
        self.name = name
    }
}

仅供参考 - 你真的想要一个可选的name吗？