ios - 无法实例化函数 无法转换类型为 '__NSArrayI' 的值

Question

我在 Swift 3 中实现了以下功能:

    func parseJSON() {
    var JsonResult: NSMutableArray = NSMutableArray()

    do {
        JsonResult = try JSONSerialization.jsonObject(with: self.data as Data, options:JSONSerialization.ReadingOptions.allowFragments) as! NSMutableArray
    } catch let error as NSError {
        print(error)
    }
    var jsonElement:NSDictionary=NSDictionary()
    let locations: NSMutableArray = NSMutableArray()

    for i in 0 ..< JsonResult.count
    {
        jsonElement = JsonResult[i] as! NSDictionary
        let location = Parsexml()

        if let title = jsonElement["Title"] as? String,
            let body = jsonElement["Body"] as? String,
            let userId = jsonElement["UserId"] as? Int,
            let Id = jsonElement["Id"] as? Int
        {

            location.title = title
            location.body = body
            location.userId = userId
            location.id = Id

        }

        locations.add(location)
    }
    DispatchQueue.main.async { () -> Void in

        self.delegate.itemsDownloaded(items: locations)

    }

当我从另一个方法调用此函数时，出现以下错误:

Could not cast value of type '__NSArrayI' (0x105d4fc08) to 'NSMutableArray' (0x105d4fcd0).

它指向这里的元素:

  JsonResult = try JSONSerialization.jsonObject(with: self.data as Data, options:JSONSerialization.ReadingOptions.allowFragments) as! NSMutableArray

它以 SIGBRT 退出的地方..

我在这里错过了什么？

Answer 1

您正在尝试将 NSArray 转换为 NSMutable 数组，这是警告所提示的内容。

获取它提供给您的数组，然后将其转换为可变数组。

let jsonArray = try JSONSerialization.jsonObject(with: self.data as Data, options:JSONSerialization.ReadingOptions.allowFragments) as! NSArray
jsonResult = jsonArray.mutableCopy() as! NSMutableArray

无关，但您可能还希望为 JsonResult 使用小写值以符合正常的 iOS 样式指南。它应该改为 jsonResult。