swift do-catch 中未解决的已识别错误

Question

感谢社区，我昨天在迁移到 swift 2 时解决了错误处理问题。这些更正实际上产生了一个新错误，我不知道如何更正它。以下是当前代码，它在提要中显示一些图片帖子：

override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)

ParseHelper.timelineRequestForCurrentUser {
  (result: [AnyObject]?, error: NSError?) -> Void in
  self.posts = result as? [Post] ?? []

  for post in self.posts {
    do
    {
      let data = try post.imageFile?.getData()
    }
    catch
    {
      print("Error: \(error)")
      //Handle the error instead of print probably
    }
    post.image = UIImage(data: data!, scale:1.0)  --> where I get the error message "Use of unresolved identified 'data'"

  }

  self.tableView.reloadData()
}

另外，我在之前的方法中提到的 ParseHelper 文件中出现了一个新错误。

static func timelineRequestForCurrentUser(completionBlock: PFArrayResultBlock) {
let followingQuery = PFQuery(className: "Follow")
followingQuery.whereKey("fromUser", equalTo:PFUser.currentUser()!)

let postsFromFollowedUsers = Post.query()
postsFromFollowedUsers!.whereKey("user", matchesKey: "toUser", inQuery: followingQuery)

let postsFromThisUser = Post.query()
postsFromThisUser!.whereKey("user", equalTo: PFUser.currentUser()!)

let query = PFQuery.orQueryWithSubqueries([postsFromFollowedUsers!, postsFromThisUser!])
query.includeKey("user")
query.orderByDescending("createdAt")

// 3
query.findObjectsInBackgroundWithBlock(completionBlock) --> I get an error message too here "Cannot convert value of type 'PFArrayResultBlock' to expected argument type 'PFQueryArrayResultBlock?'"

Answer 1

对 Swift 没有太多经验，但编译器输出很有意义。首先，let data 声明的范围仅限于 do/catch 的 do 块。为了让catch 块使用数据，必须在 do/catch 周围的范围内重新声明数据...

let data : NSData? // assuming type is NSData (my point here is about scope)
do {
    data = try post.imageFile?.getData()
} catch {
    print("Error: \(error)")
    //Handle the error instead of print probably
}
// now data is in scope here...
post.image = UIImage(data: data!, scale:1.0)

第二个问题似乎是完成块在这里被声明为PFArrayResultBlock 类型的函数参数：

static func timelineRequestForCurrentUser(completionBlock: PFArrayResultBlock)

...但是 parse 期望将 PFQueryArrayResultBlock 类型的块传递给 findObjectsInBackground。看起来它们之间的区别是数组元素的预期类型略有不同（[PFObject]? 用于查询，[AnyObject]?）。

Answer 2

这就是我纠正问题的方式：

override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated) 
ParseHelper.timelineRequestForCurrentUser { 
(result: [PFObject]?, error: NSError?) -> Void in 
self.posts = result as? [Post] ?? [] 
self.tableView.reloadData() } }