Swift中的字典访问

Question

请考虑以下代码,该代码从plist获取字典数组:

let path = NSBundle.mainBundle().pathForResource("books", ofType: "plist")
let dict = NSDictionary(contentsOfFile: path)
let books:Array = dict.objectForKey("Books") as Array<Dictionary<String, AnyObject>> //I hate how ugly and specific this is. There has got to be a better way??? Why can't I just say let books:Array = dict.objectForKey("Books")?

let rnd = Int(arc4random_uniform((UInt32(books.count))))
let bookData:Dictionary = books[rnd]

现在,我无法访问单个图书词典:

let title:String = bookData.objectForKey("title") //[String: AnyObject] does not have a member named 'objectForKey'

let title:String = bookData["title"] // (String, AnyObject) is not convertible to String 

找到这本书名称的正确方法是什么？

Answer 1

你可以使用Beta 3的Arrays和Dictionaries的新语法糖.

let path = NSBundle.mainBundle().pathForResource("books", ofType: "plist")
let dict = NSDictionary(contentsOfFile: path)
let books = dict.objectForKey("Books")! as [[String:AnyObject]]

您可以bookData按原样访问,自动类型推断应该工作...

let rnd = Int(arc4random_uniform((UInt32(books.count))))
let bookData = books[rnd]

为书籍词典中的每个项目添加一个显式类型,因为我们已将其定义为AnyObject.

let title = bookData["title"]! as String
let numPages = bookData["pages"]! as Int

晚编辑

• 使用nil合并运算符,??您可以检查nil值并提供如下的备用值:

  let title = (bookData["title"] as? String) ?? "untitled"
  let numPages = (bookData["pages"] as? Int) ?? -1