迅速1.2 NSDate?！不可转换为NSDate
迅速1.2 NSDate?！不可转换为NSDate
提问于 2015-05-09 10:30:16
升级到1.2之后，我有编译错误：
NSDate?! is not convertible to NSDate代码：
let dateCreated = photoCommentObjects[indexPath.row].createdAt as NSDate其他企图：
我也试过：
let dateCreated = photoCommentObjects[indexPath.row].createdAt as? NSDate我得到了错误：
Downcast from NSDate?! to 'NSDate' only unwraps optionals回答 3
Stack Overflow用户
回答已采纳
发布于 2015-05-09 11:37:21
显然，photoCommentObjects[indexPath.row].createdAt正在返回一种NSDate?!类型，它是一个可选选项的隐式包装可选。若要将其解封，首先将结果强制转换为NSDate?和as，以删除隐式包装的可选选项，然后使用可选绑定来解包装结果的NSDate?。
if let dateCreated = photoCommentObjects[indexPath.row].createdAt as NSDate? {
// use dateCreated which is of type NSDate
}其结果是dateCreated将是一个普通的NSDate。
或者，您可以使用：
if let temp = photoCommentObjects[indexPath.row].createdAt, dateCreated = temp {
// each assignment unwraps one layer of Optional
// use dateCreated which is of type NSDate
} else {
println("something is nil")
}Stack Overflow用户
发布于 2015-05-09 10:33:44
这是一个类型问题。您有一个具有AnyObject类型的数组，并且无法读取AnyObject上的属性。
//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].createdAtStack Overflow用户
发布于 2015-05-09 10:58:42
你试过吗？
let dateCreated = photoCommentObjects[indexPath.row].createdAt as! NSDate从SIFT1.2开始，您必须使用!显式标记强制转换。这提醒您，如果失败，您的应用程序将崩溃。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/30138832
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