我在运行模拟器时一直收到这个 fatal error ，我不知道如何解决。我正在使用 Parse 创建一个模拟 Instagram 项目，由于某种原因，我收到一个 fatal error 和一个线程 1:
query.whereKey("follower", equalTo: PFUser.currentUser()!.objectId!)
我知道这是一个常见问题，因为我查看了许多包含此 fatal error 的问题。但是，我对 Swift 编程还很陌生，所以我很困惑，如果有人能帮助我，我将不胜感激，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()
}
}
})
}
}
}
最佳答案
您可能没有以任何用户身份登录，因此 PFUser.currentUser() 返回 nil 并且当您强制解包时它会产生错误，因为您无法解包 nil 值.
首先检查是否有用户登录使用:
if let user = PFUser.currentUser(){
println("User logged, lets do this")
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()
}
}
})
} else {
println("No user logged, ops!")
}
关于ios - swift: fatal error :在展开可选值 (lldb) 时意外发现 nil，线程 1，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30678934/