所以我有以下代码块：
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
// Recall cell to call further cell data
let cell = tableView.cellForRow(at: indexPath) as! FollowersCell
var i: Int = 0;
// if user tapped on himself, go home. If not, go guest
if cell.usernameLabel.text == PFUser.current()!.username! {
let home = self.storyboard?.instantiateViewController(withIdentifier: "HomeViewController") as! HomeViewController
self.navigationController?.pushViewController(home, animated: true)
} else {
print("You made it inside the else - clause")
print(cell.usernameLabel.text!) // this prints out the correct username no matter which user I click on
guestName.append(cell.usernameLabel.text!)
print(guestName[i]) // this should print out the same as cell.usernameLabel.text (I think?) but only prints out whichever user I press the first time during runtime
print(i) // this should print 0,1,2,3,... incrementing each time I press a given user, but it always prints only 0
i = i + 1 // incrementing i by one
let guest = self.storyboard?.instantiateViewController(withIdentifier: "GuestViewController") as? GuestViewController
print("Made it this far")
if guest == nil {
print("The view controller is nil for some reason")
} else {
print("The view controller is not nil but it still doesn't work")
}
//self.navigationController?.pushViewController(guest!, animated: true)
}
}
每当我点击应该调用此函数的视图时，都会在日志中打印以下内容：
You made it inside the else - clause
test3
test3
0
Made it this far
The view controller is not nil but it still doesn't work
正如您所看到的，我已经提供了一些检查点和行，以打印出有关我的程序状态的信息，并且我在代码中也添加了一些注释，请查看这些注释因为他们解释了我遇到麻烦的一些事情。然而，这是导致我最麻烦的最后一行（被评论出来的）。出于某种原因，每当我取消注释该行时，我的应用程序崩溃时出现以下错误：Error message，我在日志中收到以下消息：
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)
是否有人能够看到问题所在？从代码中可以看出，我试图推送的视图控制器不是零。我已经被困在这几天了，似乎无法弄明白。
EDIT 这里是GuestViewController：
import UIKit
import Parse
var guestName = [String]()
class GuestViewController: UICollectionViewController {
// UI Objects
var refresher: UIRefreshControl!
var page: Int = 10
// Arrays to hold data from server
var uuidArray = [String]()
var pictureArray = [PFFile]()
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView!.alwaysBounceVertical = true
self.navigationItem.title = guestName.last?.uppercased()
self.navigationItem.hidesBackButton = true
let backButton = UIBarButtonItem(title: "Back", style: .plain, target: self, action: #selector(GuestViewController.back(_:)))
self.navigationItem.leftBarButtonItem = backButton
// Swipe to go back
let backSwipe = UISwipeGestureRecognizer(target: self, action: #selector(GuestViewController.back(_:)))
backSwipe.direction = UISwipeGestureRecognizerDirection.right
self.view.addGestureRecognizer(backSwipe)
// Pull to refresh
refresher = UIRefreshControl()
refresher.addTarget(self, action: #selector(GuestViewController.refresh), for: UIControlEvents.valueChanged)
collectionView?.addSubview(refresher)
// Load posts
loadPosts()
}
func back(_ sender : UIBarButtonItem) {
_ = self.navigationController?.popViewController(animated: true)
if !guestName.isEmpty {
guestName.removeLast()
}
}
func refresh() {
collectionView?.reloadData()
refresher.endRefreshing()
}
func loadPosts() {
let query = PFQuery(className: "posts")
query.whereKey("username", equalTo: guestName.last!)
query.limit = page
query.findObjectsInBackground { (objects, error) in
if error != nil {
print(error!.localizedDescription)
} else {
for object in objects! {
self.uuidArray.append(object.value(forKey: "uuid") as! String)
self.pictureArray.append(object.value(forKey: "picture") as! PFFile)
}
self.collectionView?.reloadData()
}
}
}
// Cell number
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return pictureArray.count
}
// Cell configuration
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! pictureCell
pictureArray[indexPath.row].getDataInBackground { (data, error) in
if error != nil {
print(error!.localizedDescription)
} else {
cell.picture.image = UIImage(data: data!)
}
}
return cell
}
// header configuration
override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let header = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "Header", for: indexPath) as! HeaderViewController
// Load data of guest
let infoQuery = PFQuery(className: "_User")
infoQuery.whereKey("username", equalTo: guestName.last!)
infoQuery.findObjectsInBackground { (objects, error) in
if error != nil {
print(error!.localizedDescription)
} else {
// shown wrong user
if objects!.isEmpty {
print("Wrong user")
}
// find user information
for object in objects! {
header.fullnameLabel.text = (object.object(forKey: "fullname") as? String)?.uppercased()
header.bioLabel.text = object.object(forKey: "bio") as? String
header.bioLabel.sizeToFit()
let profilePictureFile: PFFile = (object.object(forKey: "profilePicture") as? PFFile)!
profilePictureFile.getDataInBackground(block: { (data, error) in
header.profilePicture.image = UIImage(data: data!)
})
}
}
}
// Show if current user is following guest
let followQuery = PFQuery(className: "Follow")
followQuery.whereKey("follower", equalTo: PFUser.current()!.username!)
followQuery.whereKey("following", equalTo: guestName.last!)
followQuery.countObjectsInBackground { (count, error) in
if error != nil {
print(error!.localizedDescription)
} else {
if count == 0 {
header.profileButton.setTitle("Follow", for: .normal)
header.bioLabel.backgroundColor = .lightGray
} else {
header.profileButton.setTitle("Following", for: .normal)
header.profileButton.backgroundColor = .green
}
}
}
// Count statistics
// count posts
let posts = PFQuery(className: "posts")
posts.whereKey("username", equalTo: guestName.last!)
posts.countObjectsInBackground { (count, error) in
if error != nil {
print(error!.localizedDescription)
} else {
header.posts.text = "\(count)"
}
}
// count followers
let followers = PFQuery(className: "posts")
posts.whereKey("following", equalTo: guestName.last!)
posts.countObjectsInBackground { (count, error) in
if error != nil {
print(error!.localizedDescription)
} else {
header.followers.text = "\(count)"
}
}
// count followings
let followings = PFQuery(className: "posts")
posts.whereKey("follower", equalTo: guestName.last!)
followings.countObjectsInBackground { (count, error) in
if error != nil {
print(error!.localizedDescription)
} else {
header.following.text = "\(count)"
}
}
// Implement tap gestures
// tap to post
let postsTap = UITapGestureRecognizer(target: self, action: #selector(GuestViewController.postsTap))
postsTap.numberOfTapsRequired = 1
header.posts.isUserInteractionEnabled = true
header.posts.addGestureRecognizer(postsTap)
// tap to followers
let followersTap = UITapGestureRecognizer(target: self, action: #selector(GuestViewController.followersTap))
followersTap.numberOfTapsRequired = 1
header.followers.isUserInteractionEnabled = true
header.followers.addGestureRecognizer(followersTap)
// tap to followings
let followingsTap = UITapGestureRecognizer(target: self, action: #selector(GuestViewController.followingsTap))
followingsTap.numberOfTapsRequired = 1
header.following.isUserInteractionEnabled = true
header.following.addGestureRecognizer(followingsTap)
return header
}
func postsTap() {
if !pictureArray.isEmpty {
let index = NSIndexPath(item: 0, section: 0)
self.collectionView?.scrollToItem(at: index as IndexPath, at: UICollectionViewScrollPosition.top, animated: true)
}
}
func followersTap() {
user = guestName.last!
category = "followers"
let followers = self.storyboard?.instantiateViewController(withIdentifier: "FollowersViewController") as! FollowersViewController
self.navigationController?.pushViewController(followers, animated: true)
}
func followingsTap() {
user = guestName.last!
category = "followings"
let followings = self.storyboard?.instantiateViewController(withIdentifier: "FollowersViewController") as! FollowersViewController
self.navigationController?.pushViewController(followings, animated: true)
}
}
这里是从开始到崩溃的完整日志：
2017-03-13 20:28:26.093035 w2c7[14482:1381876] [] nw_host_stats_add_src recv too small, received 24, expected 28
2017-03-13 20:28:26.100218 w2c7[14482:1381876] [] ____nwlog_simulate_crash_inner_block_invoke dlopen CrashReporterSupport failed
2017-03-13 20:28:26.100529 w2c7[14482:1381876] [] __nwlog_err_simulate_crash simulate crash failed "nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available"
2017-03-13 20:28:26.101709 w2c7[14482:1381876] [] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.30.16
0 libsystem_network.dylib 0x000000010ea4a666 __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010f4e3006 nw_socket_add_input_handler + 3164
2 libnetwork.dylib 0x000000010f4c0555 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010f4bf572 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010f4be298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010f4d9ae1 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010f4d9510 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010f4f11f9 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000010e7c7978 _dispatch_call_block_and_release + 12
9 libdispatch.dylib 0x000000010e7f10cd _dispatch_client_callout + 8
10 libdispatch.dylib 0x000000010e7cee17 _dispatch_queue_serial_drain + 236
11 libdispatch.dylib 0x000000010e7cfb4b _dispatch_queue_invoke + 1073
12 libdispatch.dylib 0x000000010e7d2385 _dispatch_root_queue_drain + 720
13 libdispatch.dylib 0x000000010e7d2059 _dispatch_worker_thread3 + 123
14 libsystem_pthread.dylib 0x000000010eb9a4de _pthread_wqthread + 1129
15 libsystem_pthread.dylib 0x000000010eb98341 start_wqthread + 13
2017-03-13 20:28:26.119252 w2c7[14482:1381876] [] nw_host_stats_add_src recv too small, received 24, expected 28
2017-03-13 20:28:26.124506 w2c7[14482:1381876] [] __nwlog_err_simulate_crash simulate crash already simulated "nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available"
2017-03-13 20:28:26.125618 w2c7[14482:1381876] [] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.30.16
0 libsystem_network.dylib 0x000000010ea4a666 __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010f4e3006 nw_socket_add_input_handler + 3164
2 libnetwork.dylib 0x000000010f4c0555 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010f4bf572 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010f4be298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010f4d9ae1 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010f4d9510 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010f4f11f9 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000010e7c7978 _dispatch_call_block_and_release + 12
9 libdispatch.dylib 0x000000010e7f10cd _dispatch_client_callout + 8
10 libdispatch.dylib 0x000000010e7cee17 _dispatch_queue_serial_drain + 236
11 libdispatch.dylib 0x000000010e7cfb4b _dispatch_queue_invoke + 1073
12 libdispatch.dylib 0x000000010e7d2385 _dispatch_root_queue_drain + 720
13 libdispatch.dylib 0x000000010e7d2059 _dispatch_worker_thread3 + 123
14 libsystem_pthread.dylib 0x000000010eb9a4de _pthread_wqthread + 1129
15 libsystem_pthread.dylib 0x000000010eb98341 start_wqthread + 13
2017-03-13 20:28:26.127269 w2c7[14482:1381876] [] nw_host_stats_add_src recv too small, received 24, expected 28
2017-03-13 20:28:26.131263 w2c7[14482:1381876] [] __nwlog_err_simulate_crash simulate crash already simulated "nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available"
2017-03-13 20:28:26.131965 w2c7[14482:1381876] [] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.30.16
0 libsystem_network.dylib 0x000000010ea4a666 __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010f4e3006 nw_socket_add_input_handler + 3164
2 libnetwork.dylib 0x000000010f4c0555 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010f4bf572 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010f4be298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010f4d9ae1 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010f4d9510 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010f4f11f9 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000010e7c7978 _dispatch_call_block_and_release + 12
9 libdispatch.dylib 0x000000010e7f10cd _dispatch_client_callout + 8
10 libdispatch.dylib 0x000000010e7cee17 _dispatch_queue_serial_drain + 236
11 libdispatch.dylib 0x000000010e7cfb4b _dispatch_queue_invoke + 1073
12 libdispatch.dylib 0x000000010e7d2385 _dispatch_root_queue_drain + 720
13 libdispatch.dylib 0x000000010e7d2059 _dispatch_worker_thread3 + 123
14 libsystem_pthread.dylib 0x000000010eb9a4de _pthread_wqthread + 1129
15 libsystem_pthread.dylib 0x000000010eb98341 start_wqthread + 13
2017-03-13 20:28:26.133267 w2c7[14482:1381876] [] nw_host_stats_add_src recv too small, received 24, expected 28
2017-03-13 20:28:26.136343 w2c7[14482:1381876] [] __nwlog_err_simulate_crash simulate crash already simulated "nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available"
2017-03-13 20:28:26.136837 w2c7[14482:1381876] [] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.30.16
0 libsystem_network.dylib 0x000000010ea4a666 __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010f4e3006 nw_socket_add_input_handler + 3164
2 libnetwork.dylib 0x000000010f4c0555 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010f4bf572 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010f4be298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010f4d9ae1 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010f4d9510 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010f4f11f9 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000010e7c7978 _dispatch_call_block_and_release + 12
9 libdispatch.dylib 0x000000010e7f10cd _dispatch_client_callout + 8
10 libdispatch.dylib 0x000000010e7cee17 _dispatch_queue_serial_drain + 236
11 libdispatch.dylib 0x000000010e7cfb4b _dispatch_queue_invoke + 1073
12 libdispatch.dylib 0x000000010e7d2385 _dispatch_root_queue_drain + 720
13 libdispatch.dylib 0x000000010e7d2059 _dispatch_worker_thread3 + 123
14 libsystem_pthread.dylib 0x000000010eb9a4de _pthread_wqthread + 1129
15 libsystem_pthread.dylib 0x000000010eb98341 start_wqthread + 13
Followings loaded
2017-03-13 20:28:30.369257 w2c7[14482:1381917] [] nw_host_stats_add_src recv too small, received 24, expected 28
2017-03-13 20:28:30.373519 w2c7[14482:1381917] [] __nwlog_err_simulate_crash simulate crash already simulated "nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available"
2017-03-13 20:28:30.374350 w2c7[14482:1381917] [] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.30.16
0 libsystem_network.dylib 0x000000010ea4a666 __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010f4e3006 nw_socket_add_input_handler + 3164
2 libnetwork.dylib 0x000000010f4c0555 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010f4bf572 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010f4be298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010f4d9ae1 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010f4d9510 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010f4f11f9 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000010e7c7978 _dispatch_call_block_and_release + 12
9 libdispatch.dylib 0x000000010e7f10cd _dispatch_client_callout + 8
10 libdispatch.dylib 0x000000010e7cee17 _dispatch_queue_serial_drain + 236
11 libdispatch.dylib 0x000000010e7cfb4b _dispatch_queue_invoke + 1073
12 libdispatch.dylib 0x000000010e7d2385 _dispatch_root_queue_drain + 720
13 libdispatch.dylib 0x000000010e7d2059 _dispatch_worker_thread3 + 123
14 libsystem_pthread.dylib 0x000000010eb9a4de _pthread_wqthread + 1129
15 libsystem_pthread.dylib 0x000000010eb98341 start_wqthread + 13
2017-03-13 20:28:30.993304 w2c7[14482:1381876] [] nw_host_stats_add_src recv too small, received 24, expected 28
2017-03-13 20:28:30.996557 w2c7[14482:1381876] [] __nwlog_err_simulate_crash simulate crash already simulated "nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available"
2017-03-13 20:28:30.997102 w2c7[14482:1381876] [] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.30.16
0 libsystem_network.dylib 0x000000010ea4a666 __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010f4e3006 nw_socket_add_input_handler + 3164
2 libnetwork.dylib 0x000000010f4c0555 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010f4bf572 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010f4be298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010f4d9ae1 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010f4d9510 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010f4f11f9 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000010e7c7978 _dispatch_call_block_and_release + 12
9 libdispatch.dylib 0x000000010e7f10cd _dispatch_client_callout + 8
10 libdispatch.dylib 0x000000010e7cee17 _dispatch_queue_serial_drain + 236
11 libdispatch.dylib 0x000000010e7cfb4b _dispatch_queue_invoke + 1073
12 libdispatch.dylib 0x000000010e7d2385 _dispatch_root_queue_drain + 720
13 libdispatch.dylib 0x000000010e7d2059 _dispatch_worker_thread3 + 123
14 libsystem_pthread.dylib 0x000000010eb9a4de _pthread_wqthread + 1129
15 libsystem_pthread.dylib 0x000000010eb98341 start_wqthread + 13
You made it inside the else - clause
test3
test3
0
Made it this far
The view controller is not nil but it still doesn't work
答案 0 :(得分：0)
在包含GuestViewController的实际故事板本身上，是故事板ID设置吗？在拼写/大小写方面，它是否与您在代码中设置的完全相同？此外，对于这行代码，而不是“as”之后的问号，将其置于“！”。
let guest = self.storyboard?.instantiateViewController(withIdentifier: "GuestViewController") as? GuestViewController.
您是否确定故事板上的GuestViewController，该类未设置？或者可能设置错误的班级？最后，您确定所有内容都嵌入在NavigationController中吗？
答案 1 :(得分：0)
经过近一年的时间，你肯定必须解决它，但为了以防万一，检查一下，如果你从故事板中的另一个VC复制并粘贴了组件，那么这些组件的出口是＆＃34;拔掉的＆ ＃34;或在故事板中删除，用于该VC
答案 2 :(得分：-1)
在调用guest后推送视图控制器时，请在没有感叹号的情况下尝试。或者在您设置GuestViewController值的行中guest之后添加一个惊叹号。这样做会将其声明为Optional（GuestViewController）。这意味着您的变量可以是GuestViewController，也可以是nil。
如果您未将其声明为Optional，则未定义引用guest!。此外，如果您尚未将其声明为Optional，则无需检查它是否为nil。
答案 3 :(得分：-2)
你确定你的ViewController是NavigationController的孩子吗？ 你尝试过测试了吗？
{{1}}