无法从 JSON 中提取数组

Can't Extract Array from JSON

我正在尝试解析来自我的服务器的 JSON 格式的响应。

这是我的代码的第一部分:

// (responseBody is of type NSData)
guard let dictionary = try? NSJSONSerialization.JSONObjectWithData(responseBody!, options: [.MutableContainers]) else{
    fatalError("JSON Root Dictionary Not Found")
}

print("Dictionary: \(dictionary)")

...日志正确给出:

Dictionary: {
    count = 1;
    date = "2015-12-22T13:16:17.727";
    items =     (
                {
            attribute1 = null;
            attribute2 = null;
            attribute3 = null;
            date = "2015-12-22T17:30:52.764";
            size = 9175;
            version = 19;
        }
    );
}

(不相关的字段省略,相关字段名称和值更改为保密)

...所以键 items 的值似乎是一个符合 "an array of dictionaries, each with keys of type String and values of type Any" 的对象。

接下来,获取items数组:

guard let count = dictionary["count"] as? Int else {
    fatalError("Item Count Not Found")
}

guard count > 0 else {
    fatalError("Item Count Is Zero")
}

guard let items = dictionary["items"]! else{
    fatalError("Items Array Not Found")
}

if items is Array<Any> { 
    // THIS TEST FAILS (SHOULD PASS?)
    print("Items is an array")
}
else if items is Dictionary<String, Any> {
    // THIS TEST FAILS, TOO (JUST OUT OF DESPERATION...)
    print("Items is a dictionary")
}
else{
    // ...SO THIS CODE RUNS.
    print("Really? \(items)")
}

但是 - 正如上面代码中的注释所解释的那样 - 我无法将其转换为数组,而是执行了最后一个 print() 调用(print("Really? \(items)")),给出:

Really? (
        {
        attribute1 = null;
        attribute2 = null;
        attribute3 = null;
        date = "2015-12-22T17:30:52.764";
        size = 9175;
        version = 19;
    }
)

...所以,items 的类型是什么?我如何获得我的数组?

也许我遗漏了一些关于 Swift 的集合类型的信息?


注意: 起初我怀疑数组元素是用圆括号 (()) 而不是方括号 ([]) 括起来的。但是,字典和数组的控制台输出似乎遵循这种格式,如 the answers to this question.

中所述

更新: 根据@Paulw11 在下面评论中给出的提示,我使用以下代码解决了这个问题:

guard let items = dictionary["items"]! as? NSMutableArray else{
    fatalError("Items Array Not Found")
}

for element in documents {               // I wish I could combine these                 
    let item = element as! NSDictionary  // two lines into one (enumeration and cast)

    print("Item: \(item)")
}

...但是,我仍然不清楚如何实施不依赖 Foundation 类.

的纯 Swift 解决方案

更新 2: 我正在尝试使用以下代码将 NSMutableArray 转换为本机 Swift 数组:

if var nativeItems = items as? [[String: AnyObject]] {

}

但这给了我:

WARNING: Cast from 'NSMutableArray' to unrelated type '[[String : AnyObject]]' always fails

if块的位置,并且(等待它):

ERROR: Call can throw, but it is not marked with 'try' and the error is not handled.

...在 AppDelegate.swift(CoreData 样板),完全相同的症状

CoreData 代码一直在编译。 如果我注释掉 if var nativeItems = items... 转换,错误就会消失。更改变量名称无效。确实。巫毒

幸运的是,我可以通过扩展样板 lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {... 部分中的 catch 子句来绕过它:

catch let error as NSError {
        // Report any error we got.

        print("Error: \(error)")

        var dict = [String: AnyObject]()

        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"

        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        dict[NSUnderlyingErrorKey] = error as NSError

        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)

        // TODO: Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and 
        // terminate. You should not use this function in a shipping 
        // application, although it may be useful during development.

        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")

        abort()
    }

    return coordinator
}() 

对此:

catch let error as NSError {
        // Report any error we got.

        print("Error: \(error)")

        var dict = [String: AnyObject]()

        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"

        dict[NSLocalizedFailureReasonErrorKey] = failureReason

        dict[NSUnderlyingErrorKey] = error as NSError

        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)

        // TODO: Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and 
        // terminate. You should not use this function in a shipping 
        // application, although it may be useful during development.

        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")

        abort()
    }
    catch {
        // << ADDED THIS "CATCH-ALL" >>
        fatalError()
    }

    return coordinator
}() 

...令人惊讶的是,上面的警告 ("cast always fails") 是没有根据的,代码执行得很完美...

说真的,苹果?

正如您已经发现的那样,它 returns 是 NSMutableDictionaryNSMutableArray。将其转换为 Swift 中的字典数组:

if var items = items as? [[String: AnyObject]] {
    print(items[0])
} else {
    print("Really?")
}

这就是为什么我更喜欢 SwiftyJSON 而不是 NSJSONSerializer 的原因。

您看到的 if var 可能比 if let 少很多。 if var 用于保持数组可变,因为您指定了 MutableContainers 选项。

let itemsArray:NSMutableArray = NSMutableArray()

itemsArray = dictionary["items"]

print(itemsArray)

这样试试..