初始值设定条件的结合必须有可选的类型，而不是“日期”

问题描述：

但我不知道发生什么。我一直在寻找，我认为这可能是关于铸造和可选的。第一个给初始值设定条件的结合必须有可选的类型，而不是“日期”第二和第三给人初始值设定为有条件的结合必须有可选的类型，而不是“双”

for article in (topic.articleArrays ?? nil)!{ 
      if let articleId = article.id, 
      let articleHeadline = article.headline, 
      let articleSummary = article.summary, 
      let articleCity = article.city, 
      let articleState = article.state, 
      let articleDateretrieved = article.dateRetrieved, 
      let articlePublisher = article.publisher, 
      let articleLatitude = article.latitude, 
      let articleLongitude = article.longitude, 
      let articleRawBaseUrl = article.rawBaseUrl, 
      let articleRawUrl = article.rawUrl { 
       editedArticles?.append(NewsArticle(id: articleId, headline: articleHeadline, publisher: articlePublisher, summary: articleSummary, rawUrl: articleRawUrl, rawBaseUrl: articleRawBaseUrl, retrieved_date: articleDateretrieved, city: articleCity, state: articleState, latitude: articleLatitude, longitude: articleLongitude)) 
      } 
     }

的为结构ediedArticles是NewsArticle我已经下面

struct NewsArticle { 
var id: String 
var headline: String 
var publisher: String 
var summary: String 
var rawUrl: String 
var rawBaseUrl: String 
var retrieved_date: Date 
var city: String 
var state: String 
var latitude: Double 
var longitude: Double 
init(id: String, headline: String, publisher: String, summary: String, rawUrl: String, rawBaseUrl: String, retrieved_date: Date, city: String, state: String, latitude: Double, longitude: Double) { 
    self.id = id 
    self.headline = headline 
    self.publisher = publisher 
    self.summary = summary 
    self.rawUrl = rawUrl 
    self.rawBaseUrl = rawBaseUrl 
    self.retrieved_date = retrieved_date 
    self.city = city 
    self.state = state 
    self.latitude = latitude 
    self.longitude = longitude 
    } 
}

topic.articlesArray列出具有不同的数据结构类型，是SavedArticle（CoreData）

var articleArrays: [SavedArticle]? { 
    return self.articles?.allObjects as? [SavedArticle] 
}

，并有SavedArticle-CoreDataClass

var dateRetrieved: Date { 
    get { 
     return retrieved_date as Date 
    } 
    set(newDate) { 
     retrieved_date = newDate as NSDate 
    } 
} 

// TODO: Figured it out how to stored corrdinates in [Double] 

convenience init?(id: String, headline: String, publisher: String, summary: String, retrieved_date: Date, city: String, state: String, latitude: Double, longitude: Double) { 

    guard let context = NaberCoreDataHandler.sharedInstance.managedContext else { return nil } 
    self.init(entity: SavedArticle.entity(), insertInto: context) 

    self.id = id 
    self.headline = headline 
    self.publisher = publisher 
    self.summary = summary 
    self.dateRetrieved = retrieved_date 
    self.city = city 
    self.state = state 
    self.latitude = latitude 
    self.longitude = longitude 
}

与以下

@NSManaged public var city: String? 
@NSManaged public var headline: String? 
@NSManaged public var id: String? 
@NSManaged public var publisher: String? 
@NSManaged public var rawBaseUrl: String? 
@NSManaged public var rawUrl: String? 
@NSManaged public var retrieved_date: NSDate 
@NSManaged public var state: String? 
@NSManaged public var summary: String? 
@NSManaged public var latitude: Double 
@NSManaged public var longitude: Double 
@NSManaged public var topics: SavedTopic?

的SavedArticle-CoreDataProperties这将是真棒，如果有人能帮助我想通了什么问题。我一整天都在争吵，没有任何帮助。谢谢！ :)

答

if let（和guard let）只能用于展开可选值。您可以在单独的一行中使用常规的let语句分配这些值，或者直接将它们传递给函数，因为它们不需要解包。

请注意，如果数组为零，'（topic.articleArrays ?? nil）！'仍然会导致运行时错误。您可能想使用'（topic.articleArrays []）'代替。 –

非常感谢！ – thunpisit

答

article.dateRetrieved，article.latitude和article.longitude不是可选项。他们没有声明？在他们的名字后面，所以他们永远不会是零。因此，没有必要 - 实际上这是一个错误 - 尝试用“if let”声明对它们进行解包。

删除编译器抱怨的三行代码。

当您创建NewsArticle并将其附加到editedArticles时，可以将文章的这些属性直接传递给NewsArticle的构造函数。

非常感谢！ – thunpisit

初始值设定条件的结合必须有可选的类型，而不是“日期”

相关推荐