升级到xcode 6.4后，我无法解开可选项。这是我在运行这行代码时遇到的错误：
query.whereKey("follower", equalTo: PFUser.currentUser()!.objectId!)
致命错误：在展开Optional值时意外发现nil （LLDB）
我知道，对于xcode的新更新，您必须更加谨慎地展开选项，但我不确定我需要做出哪些更改才能快速合作。我已经尝试了许多不同的方式，这些方法在S / O上提出但尚未得到一个工作方式。这是我的完整代码：
谢谢！
import UIKit
import Parse
class TableViewController: UITableViewController {
var usernames = [""]
var userids = [""]
var isFollowing = ["":false]
override func viewDidLoad() {
super.viewDidLoad()
var query = PFUser.query()
query?.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if let users = objects {
self.usernames.removeAll(keepCapacity: true)
self.userids.removeAll(keepCapacity: true)
self.isFollowing.removeAll(keepCapacity: true)
for object in users {
if let user = object as? PFUser {
if user.objectId! != PFUser.currentUser()?.objectId {
self.usernames.append(user.username!)
self.userids.append(user.objectId!)
var query = PFQuery(className: "followers")
***query.whereKey("follower", equalTo: PFUser.currentUser()!.objectId!)***
query.whereKey("following", equalTo: user.objectId!)
query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if let objects = objects {
if objects.count > 0 {
self.isFollowing[user.objectId!] = true
} else {
self.isFollowing[user.objectId!] = false
}
}
if self.isFollowing.count == self.usernames.count {
self.tableView.reloadData()
}
})
}
}
}
}
})
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete method implementation.
// Return the number of rows in the section.
return usernames.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("cell", forIndexPath: indexPath) as! UITableViewCell
cell.textLabel?.text = usernames[indexPath.row]
let followedObjectId = userids[indexPath.row]
if isFollowing[followedObjectId] == true {
cell.accessoryType = UITableViewCellAccessoryType.Checkmark
}
return cell
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
var cell:UITableViewCell = tableView.cellForRowAtIndexPath(indexPath)!
let followedObjectId = userids[indexPath.row]
if isFollowing[followedObjectId] == false {
isFollowing[followedObjectId] = true
cell.accessoryType = UITableViewCellAccessoryType.Checkmark
var following = PFObject(className: "followers")
following["following"] = userids[indexPath.row]
following["follower"] = PFUser.currentUser()?.objectId
following.saveInBackground()
} else {
isFollowing[followedObjectId] = false
cell.accessoryType = UITableViewCellAccessoryType.None
var query = PFQuery(className: "followers")
query.whereKey("follower", equalTo: PFUser.currentUser()!.objectId!)
query.whereKey("following", equalTo: userids[indexPath.row])
query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in
if let objects = objects {
for object in objects {
object.deleteInBackground()
}
}
})
}
}
}
答案 0 :(得分：0)
您可以使用Optional Binding访问已登录的用户，以确保在将其用作查询参数之前不是nil。
所以你应该换行：
query.whereKey("follower", equalTo: PFUser.currentUser()!.objectId!)
使用：
if let userObj = PFUser.currentUser()?.objectId {
query.whereKey("follower", equalTo: userObj)
}
现在这将解决您的错误并防止您的应用崩溃，但也许您应该重新构建您的应用，以确认用户已登录，无论何时到达此UITableViewController。
在任何情况下，您仍应使用Optional Binding来防止潜在的崩溃。