swift 1.2 NSDate？!不可转换为 NSDate

Question

升级到1.2后出现编译错误:

NSDate?! is not convertible to NSDate

代码:

let dateCreated = photoCommentObjects[indexPath.row].createdAt as NSDate

其他尝试:

我也试过:

let dateCreated = photoCommentObjects[indexPath.row].createdAt as? NSDate

我得到错误:

Downcast from NSDate?! to 'NSDate' only unwraps optionals

Answer 1

这是一个类型问题。您有一个 AnyObject 类型的数组，您无法读取 AnyObject 的属性。

//sample data
class PhotoComment {
   let createdAt = NSDate()
}

let photoCommentObjects: [AnyObject] = [PhotoComment()]

//let's get the indexed object first and let's cast it from AnyObject
let photoComment = photoCommentObjects[indexPath.row] as! PhotoComment
//now trivially
let dateCreated = photoComment.createdAt

或

//let's cast the whole array first
let photoComments = photoCommentObjects as! [PhotoComment]
let dateCreated = photoComments[indexPath.row].createdAt