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swift - 可选类型的值必须被解包以引用成员，但它是隐式解包的可选属性

问题描述

为什么我会得到这个？它是一个隐式展开的可选属性。我不认为我应该得到这个错误。我尝试清理我的构建文件夹并删除派生数据，然后关闭 Xcode。没有任何效果。

var questionsWrap: QuestionsWrapper
    
func userMadeSelection(
    _ responseId: Int,
    _ myTheir: Question.Response.Selections.MyTheir,
    _ choice: Question.Response.Selections.MyTheir.Choice
) {
    guard let id = question.id else { return }
    questionsWrap.saveSelection(
        questionId: id,
        responseID: responseId,
        myTheir: myTheir,
       choice: choice
    ) { success in
        if !success {
           AlertViewController<Any>.alertFailure(
               message:  "We made a mistake and we weren't able to save your selection."
            )
        }
    }
    singleQuestionDataSource.observableQuestion.value = question
    print(#line, "userMadeSelectionImportance: \(responseId) \(myTheir) \(choice)")
    if choice.changedBetweenPolarAndNeutral(
        with: questionsWrap.question.theirInteractionStyle
        ) {
        let presenter = Question.Importance.Presenter(question)
        update(presenter?.importance)
        questionCell?.importancePresenter = presenter
    }
}

方法定义

func saveSelection(
    questionId: Int,
    responseID: Int,
    myTheir: Question.Response.Selections.MyTheir,
    choice: Question.Response.Selections.MyTheir.Choice,
    context: Context,
    successAction: SuccessAction? = nil
) {
        
        guard let questionIndex = questions.index(of: questionId),
            let responseIndex = questions[questionIndex].responses.index(of: responseID) else {
                successAction?(false)
                return
        }
        
        questions[questionIndex].responses[responseIndex].set(myTheir, choice, for: context)
        let response = questions[questionIndex].responses[responseIndex]
        URL.make(
           my: response.choice(for: .my, UserDefaults.questionContext),
           their: response.choice(for: .their, UserDefaults.questionContext),
           forResponseID: responseID,
           forQuestionID: questionId,
           forContext: UserDefaults.questionContext
           ).get { jsonDict in
            successAction?(jsonDict.success)
        }
    }

不幸的是，我不知道提供什么代码来原子地重新创建这个问题。

我正在超越规范并发布屏幕截图以证明错误正在显示。

在此处输入图像描述

标签： swiftoptional

解决方案

使用隐式展开的 Optional 看到此错误消息的通常原因是隐式展开不会通过赋值来传播自身。例如，这是合法的：

    var s : String!
    print(s.count)

但这不是：

    let s2 = s
    print(s2.count) // value must be unwrapped

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