Hi,
I’ve been trying to refresh a view to reload its data,
for example, let’s say the user has a name called Bill,
if im going to another view to change his name to Jack,
when Im going back to the previous view to see his name changed,
it’s still Bill, only if I’m running the app again it’s showing the changed result- Jack.
Is there a way to refresh the view every time I’m going back to that view?
The standard approach is to repopulate all your view objects (labels, text fields etc.) in your view controller’s viewWillAppear. Or depending on how your app is structured, you might need some sort of notification (NSNotificationCenter works well) that the view controller would respond to when the model data changes.
Typically when there are problems in this area, it’s because you have not separated the view from the model, in your mind at least. It may be useful to read up on the MVC (model-view-controller) design pattern. Without seeing any of your code it’s hard to suggest anything specific though.
You can also use delegation, to update the initial view when you go back.
Typical set up as follows:
You have VC1 and VC2 ; you want to update a field in VC1 when you change a text in VC2.
Declare a protocol
protocol UpdateVC1 {
func updateName(newName: String)
}Declare that VC1 conforms to it, and implement it:
Set the delegate property of VC2 when you segue
class VC1: UIViewController, UpdateVC1 {
@IBOutlet weak var userNameField: UITextField!
func updateName(newName: String) {
userNameField.text = newName
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? VC2 {
destination.delegate = self
}
}
}In VC2 declare a delegate property:
class VC2: UIViewController {
var delegate: UpdateVC1?Then, when you change the field with name, invoke the delegate
delegate?.updateName(newName: name)Another way is to reload data in viewWillAppear (not only in viewDidload because it is not called when you return)
That’s a good idea!
Is it work for button.isHidden too?
I don’t know how to use ViewWillAppear, I tried print() and it works to print every time I open the view,
but for other things like if my data has changed, or changing text it stays the way I opened the view for the first time.
For example if I put in viewWillAppear this code:
for person in peopleWhoLike{
If person = currentUser {
likeButton.isHidden = true
unlikeButton.isHidden = false
}
}
So if the current user liked it,
for the first time I open the view the likeButton is hidden and unlikeButton isn’t.
But if im going back and the user unliked it, the second time I open the view it stays the same.
Yes, delegate can work as well to hide a button.
You use the same pattern as for
func updateName(newName: String)
by declaring
func updateButtons(likeIt: Bool)
class VC1: UIViewController, UpdateVC1 {
@IBOutlet weak var userNameField: UITextField!
@IBOutlet weak var likeButton: UIButton!
@IBOutlet weak var unlikeButton: UIButton!
func updateName(newName: String) {
userNameField.text = newName
}
func updateButtosn(likeIt: Bool) {
likeButton.isHidden = !likeIt // hidden if not likeIt
unlikeButton.isHidden = likeIt
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? VC2 {
destination.delegate = self
}
}
}You will call where needed in VC2 by
delegate?.updateButtosn(likeIt: person == currentUser)In viewWillAppear
you wrote:
If person = currentUserI suppose you mean
If person == currentUserthe code doesnt work.
Ive managed to open the second view(PostCommentController) as a present,
and if i'm doing like\unlike and when I go back,
it reloads the first view (NewsViewController) and been updated.
but if i'm on NewsViewController and I'm like\unlike, it doesnt update the PostCommentController immediately,
only when I'm presenting it for the second time.
Ive tried this:
protocol UpdateVC1 {
func updateButtons(likeIt: Bool)
}class PostCommentController: UIViewController, UITableViewDelegate, UITableViewDataSource, UpdateVC1 {
func updateButtons(likeIt: Bool) {
likeBtn.isHidden = !likeIt
unlikeBtn.isHidden = likeIt
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? NewsViewController {
destination.delegate = self
}
}
@IBOutlet weak var likeBtn: UIButton!
@IBOutlet weak var unlikeBtn: UIButton!class NewsViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource,
commentButtonDelegate {
var delegate: UpdateVC1?
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath)
-> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "postCell", for: indexPath)
as! PostCell
let inverseIndex = self.posts.count - indexPath.row - 1
cell.postImage.downloadImage(from: self.posts[inverseIndex].pathToImage)
cell.authorLabel.text = self.posts[inverseIndex].author
cell.likeLabel.text = "\(self.posts[inverseIndex].likes!) Likes"
cell.postID = self.posts[inverseIndex].postID
cell.authorImage.downloadImage(from: self.posts[inverseIndex].authorImage)
let string = self.posts[inverseIndex].timeAgo
let df = DateFormatter()
df.dateFormat = "yyyy/MM/dd, H:mm:ss"
let result = df.date(from: string!)
let timeDate = timeAgoSinceDate(result!)
cell.timeLabel.text = timeDate
cell.commentBtn.addTarget(self, action: #selector(buttonClicked(sender:)), for: .touchUpInside)
for person in self.posts[inverseIndex].peopleWhoLike{
if person == Auth.auth().currentUser!.uid{
cell.unlikeBtn.isHidden = false
cell.likeBtn.isHidden = true
delegate?.updateButtons(likeIt: person == Auth.auth().currentUser?.uid)
break
}
}
cell.indexPath = indexPath
cell.delegate = self
return cell
}How do you transition from VC1 to VC2 ?
With a segue ?
And how do you return to VC1? Do you have a nvigation controller ? Do you return with unwindSegue ?
vc1 to vc2:
func commentButtonTapped(at index: IndexPath) {
let vc = storyboard?.instantiateViewController(withIdentifier: "PostCommentController")
as? PostCommentController
let inverseIndex = self.posts.count - index.row - 1
let string = self.posts[inverseIndex].timeAgo
let df = DateFormatter()
df.dateFormat = "yyyy/MM/dd, H:mm:ss"
let result = df.date(from: string!)
let timeDate = timeAgoSinceDate(result!)
vc?.postID = self.posts[inverseIndex].postID
print(self.posts[inverseIndex].postID)
vc?.authorName = self.posts[inverseIndex].author
vc?.authorPic = self.posts[inverseIndex].authorImage
vc?.postPic = self.posts[inverseIndex].pathToImage
vc?.likesText = "\(self.posts[inverseIndex].likes!) Likes"
vc?.time = timeDate
vc?.likesCount = self.posts[inverseIndex].peopleWhoLike
self.present(vc!, animated: true, completion: nil)
}vc2 to vc1:
@IBActionfunc backButton(_ sender: Any) {
let tabVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier:
"NavigationTab") as! UITabBarController
tabVC.selectedIndex = 0
self.present(tabVC, animated: true, completion: nil)
}You should not use present() in backButton.
If you do so, you create a new instance of VC1 ! Hence, the button you have set with the delegate is the one of the old instance (that's what you did in prepare for segue), not the one of the new that you have stacked over !
Small drawing can illustrate
______________________
| VC1- 1st instance | ___________________
| VC2.delegate = me | ----- segue ----> | VC2 |
|_______button of 1st ___| creates instance| delegate = VC1.1st|
Î |___________________|
i_________ unwind or dismiss -----i |
|
______________________ |
| VC1- 2nd instance | < --- present -----------|
| | creates a new instance of VC1
|_______button of 2nd __–|
So, you should return with unwind segue (or a dismiss of VC2):
In VC1, create:
@IBAction func unwindToViewController1(_ sender: UIStoryboardSegue) {
print("I just unwind")
}In IB, control-drag from the back button to the exit at top right of VC2 window, and select unwindToViewController1
Remove the connection from backButton to backButton IBAction, and comment out the IBAction.
That should work now.
Anoter way is to dismiss VC2 in backButton.
self.dismiss(animated: true, completion: nil)
we're back at the start.
It doesn't reload the view when I dismiss\unwind so it doesnt update
if the user liked\unliked the post.
OK, so show the complete code of VC1 and VC2, to see what's happening.
SOmething not clear.
In VC1, there is only one like / unlike button, or a button in each cell ?
delegate?.updateButtons(likeIt: person == Auth.auth().currentUser?.uid)should not be in collectionView(cellForItemAt) but in the button action.
vc1:
protocol UpdateVC1 {
func updateButtons(likeIt: Bool)
}
import UIKit
import Firebase
class NewsViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource,
commentButtonDelegate {
@IBOutlet weak var collectionView: UICollectionView!
var posts = [Post]()
var AFan = [String]()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
fetchPosts()
self.view.setNeedsLayout()
self.loadView()
}
var delegate: UpdateVC1?
func fetchPosts(){
let ref = Database.database().reference()
ref.child("users").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
let users = snapshot.value as! [String : AnyObject]
for (_,value) in users {
if let uid = value["uid"] as? String{
let userImage = value["urlToImage"] as? String
if uid == Auth.auth().currentUser?.uid{
if let AFanOf = value["a fan"] as? [String : String]{
for(_,user) in AFanOf{
self.AFan.append(user)
}
}
self.AFan.append(Auth.auth().currentUser!.uid)
ref.child("posts").queryOrderedByKey().observeSingleEvent(of: .value, with: {(snap) in
for postSnapshot in snap.children.allObjects as! [DataSnapshot] {
let value = postSnapshot.value as! [String : AnyObject]
if let userID = value["userID"] as? String{
for each in self.AFan{
if each == userID{
let posst = Post()
if let author = value["author"] as? String,
let likes = value["likes"] as? Int,
let pathToImage = value["pathToImage"] as? String,
let postID = value["postID"] as? String{
posst.author = author
posst.likes = likes
posst.pathToImage = pathToImage
posst.postID = postID
posst.authorImage = userImage
if let people = value["peopleWhoLike"] as? [String : AnyObject]{
for (_,person) in people{
posst.peopleWhoLike.append(person as! String)
}
}
if let pastDate = value["createdAt"] as? String{
posst.timeAgo = pastDate
}
self.posts.append(posst)
}
}
}
self.collectionView.reloadData()
}
}
})
}
}
}
})
ref.removeAllObservers()
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.posts.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath)
-> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "postCell", for: indexPath)
as! PostCell
let inverseIndex = self.posts.count - indexPath.row - 1
cell.postImage.downloadImage(from: self.posts[inverseIndex].pathToImage)
cell.authorLabel.text = self.posts[inverseIndex].author
cell.likeLabel.text = "\(self.posts[inverseIndex].likes!) Likes"
cell.postID = self.posts[inverseIndex].postID
cell.authorImage.downloadImage(from: self.posts[inverseIndex].authorImage)
let string = self.posts[inverseIndex].timeAgo
let df = DateFormatter()
df.dateFormat = "yyyy/MM/dd, H:mm:ss"
let result = df.date(from: string!)
let timeDate = timeAgoSinceDate(result!)
cell.timeLabel.text = timeDate
cell.commentBtn.addTarget(self, action: #selector(buttonClicked(sender:)), for: .touchUpInside)
for person in self.posts[inverseIndex].peopleWhoLike{
if person == Auth.auth().currentUser!.uid{
cell.unlikeBtn.isHidden = false
cell.likeBtn.isHidden = true
delegate?.updateButtons(likeIt: person == Auth.auth().currentUser?.uid)
break
}
}
if cell.likeBtn.isHidden == true{
delegate?.updateButtons(likeIt: false)
}else{
delegate?.updateButtons(likeIt: true)
}
cell.indexPath = indexPath
cell.delegate = self
return cell
}
@objc func buttonClicked(sender:UIButton)
{
}
func commentButtonTapped(at index: IndexPath) {
let vc = storyboard?.instantiateViewController(withIdentifier: "PostCommentController")
as? PostCommentController
let inverseIndex = self.posts.count - index.row - 1
let string = self.posts[inverseIndex].timeAgo
let df = DateFormatter()
df.dateFormat = "yyyy/MM/dd, H:mm:ss"
let result = df.date(from: string!)
let timeDate = timeAgoSinceDate(result!)
vc?.postID = self.posts[inverseIndex].postID
print(self.posts[inverseIndex].postID)
vc?.authorName = self.posts[inverseIndex].author
vc?.authorPic = self.posts[inverseIndex].authorImage
vc?.postPic = self.posts[inverseIndex].pathToImage
vc?.likesText = "\(self.posts[inverseIndex].likes!) Likes"
vc?.time = timeDate
vc?.likesCount = self.posts[inverseIndex].peopleWhoLike
self.present(vc!, animated: true, completion: nil)
}
@IBAction func unwindToViewController1(_ sender: UIStoryboardSegue) {
print("I just unwind")
}
}vc2:
import UIKit
import Firebase
class PostCommentController: UIViewController, UITableViewDelegate, UITableViewDataSource, UpdateVC1 {
func updateButtons(likeIt: Bool) {
likeBtn.isHidden = !likeIt
unlikeBtn.isHidden = likeIt
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? NewsViewController {
destination.delegate = self
}
}
@IBOutlet weak var tableview: UITableView!
@IBOutlet weak var postImage: UIImageView!
@IBOutlet weak var authorLabel: UILabel!
@IBOutlet weak var likeLabel: UILabel!
@IBOutlet weak var likeBtn: UIButton!
@IBOutlet weak var unlikeBtn: UIButton!
@IBOutlet weak var authorImage: UIImageView!
@IBOutlet weak var timeLabel: UILabel!
@IBOutlet weak var backButton: UIBarButtonItem!
var postID: String!
var authorName = ""
var authorPic = ""
var postPic = ""
var likesText = ""
var time = ""
var likesCount: [String] = []
@IBAction func likePressed(_ sender: Any) {
self.likeBtn.isEnabled = false
let ref = Database.database().reference()
let keyToPost = ref.child("posts").childByAutoId().key
ref.child("posts").child(self.postID).observeSingleEvent(of: .value, with: { (snapshot) in
if let post = snapshot.value as? [String : AnyObject]{
let updateLikes: [String : Any] = ["peopleWhoLike/\(keyToPost!)" :
Auth.auth().currentUser!.uid]
ref.child("posts").child(self.postID).updateChildValues(updateLikes, withCompletionBlock: {
(error, reff) in
if error == nil{
ref.child("posts").child(self.postID).observeSingleEvent(of: .value, with: { (snap) in
if let properties = snap.value as? [String : AnyObject]{
if let likes = properties["peopleWhoLike"] as? [String : AnyObject]{
let count = likes.count
self.likeLabel.text = "\(count) Likes"
let update = ["likes" : count]
ref.child("posts").child(self.postID).updateChildValues(update)
self.likeBtn.isHidden = true
self.unlikeBtn.isHidden = false
self.likeBtn.isEnabled = true
}
}
})
}else{
}
})
}
})
ref.removeAllObservers()
}
@IBAction func unlikePressed(_ sender: Any) {
self.unlikeBtn.isEnabled = false
let ref = Database.database().reference()
ref.child("posts").child(self.postID).observeSingleEvent(of: .value, with: { (snapshot) in
if let properties = snapshot.value as? [String : AnyObject]{
if let peopleWhoLike = properties["peopleWhoLike"] as? [String : AnyObject]{
for (id,person) in peopleWhoLike{
if person as? String == Auth.auth().currentUser!.uid{
ref.child("posts").child(self.postID).child("peopleWhoLike").child(id)
.removeValue(completionBlock: { (error, reff) in
if error == nil{
ref.child("posts").child(self.postID).observeSingleEvent(of:
.value, with: { (snap) in
if let prop = snap.value as? [String : AnyObject]{
if let likes = prop["peopleWhoLike"] as? [String : AnyObject]{
let count = likes.count
self.likeLabel.text = "\(count) Likes"
ref.child("posts").child(self.postID)
.updateChildValues(["likes" : count])
}else{
self.likeLabel.text = "0 Likes"
ref.child("posts").child(self.postID)
.updateChildValues(["likes" : 0])
}
}
})
}
})
self.likeBtn.isHidden = false
self.unlikeBtn.isHidden = true
self.unlikeBtn.isEnabled = true
break
}
}
}
}
})
ref.removeAllObservers()
}
// @IBAction func backButton(_ sender: Any) {
// let tabVC = UIStoryboard(name: "Main", bundle: nil)
// .instantiateViewController(withIdentifier: "NavigationTab") as! UITabBarController
// tabVC.selectedIndex = 0
// self.present(tabVC, animated: true, completion: nil)
// }
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
authorLabel.text = authorName
authorImage.downloadImage(from: authorPic)
postImage.downloadImage(from: postPic)
likeLabel.text = likesText
timeLabel.text = time
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
for person in likesCount{
if person == Auth.auth().currentUser!.uid{
unlikeBtn.isHidden = false
likeBtn.isHidden = true
break
}
}
}
}PostCell:
import UIKit
import Firebase
protocol commentButtonDelegate {
func commentButtonTapped(at index: IndexPath)
}
class PostCell: UICollectionViewCell {
@IBOutlet weak var postImage: UIImageView!
@IBOutlet weak var authorLabel: UILabel!
@IBOutlet weak var likeLabel: UILabel!
@IBOutlet weak var likeBtn: UIButton!
@IBOutlet weak var unlikeBtn: UIButton!
@IBOutlet weak var authorImage: UIImageView!
@IBOutlet weak var commentBtn: UIButton!
@IBOutlet weak var timeLabel: UILabel!
var postID: String!
var delegate: commentButtonDelegate!
@IBAction func likePressed(_ sender: Any) {
self.likeBtn.isEnabled = false
let ref = Database.database().reference()
let keyToPost = ref.child("posts").childByAutoId().key
ref.child("posts").child(self.postID).observeSingleEvent(of: .value, with: { (snapshot) in
if let post = snapshot.value as? [String : AnyObject]{
let updateLikes: [String : Any] = ["peopleWhoLike/\(keyToPost!)" :
Auth.auth().currentUser!.uid]
ref.child("posts").child(self.postID).updateChildValues(updateLikes,
withCompletionBlock: { (error, reff) in
if error == nil{
ref.child("posts").child(self.postID).observeSingleEvent(of: .value, with: { (snap) in
if let properties = snap.value as? [String : AnyObject]{
if let likes = properties["peopleWhoLike"] as? [String : AnyObject]{
let count = likes.count
self.likeLabel.text = "\(count) Likes"
let update = ["likes" : count]
ref.child("posts").child(self.postID).updateChildValues(update)
self.likeBtn.isHidden = true
self.unlikeBtn.isHidden = false
self.likeBtn.isEnabled = true
}
}
})
}else{
print(post)
}
})
}
})
ref.removeAllObservers()
}
@IBAction func unlikePressed(_ sender: Any) {
self.unlikeBtn.isEnabled = false
let ref = Database.database().reference()
ref.child("posts").child(self.postID).observeSingleEvent(of: .value, with: { (snapshot) in
if let properties = snapshot.value as? [String : AnyObject]{
if let peopleWhoLike = properties["peopleWhoLike"] as? [String : AnyObject]{
for (id,person) in peopleWhoLike{
if person as? String == Auth.auth().currentUser!.uid{
ref.child("posts").child(self.postID).child("peopleWhoLike").child(id)
.removeValue(completionBlock: { (error, reff) in
if error == nil{
ref.child("posts").child(self.postID).observeSingleEvent(of:
.value, with: { (snap) in
if let prop = snap.value as? [String : AnyObject]{
if let likes = prop["peopleWhoLike"] as? [String : AnyObject]{
let count = likes.count
self.likeLabel.text = "\(count) Likes"
ref.child("posts").child(self.postID)
.updateChildValues(["likes" : count])
}else{
self.likeLabel.text = "0 Likes"
ref.child("posts").child(self.postID)
.updateChildValues(["likes" : 0])
}
}
})
}
})
self.likeBtn.isHidden = false
self.unlikeBtn.isHidden = true
self.unlikeBtn.isEnabled = true
break
}
}
}
}
})
ref.removeAllObservers()
}
var indexPath: IndexPath!
@IBAction func commentBtn(_ sender: UIButton) {
self.delegate?.commentButtonTapped(at: indexPath)
}
var userID: String!
}I'm a bit lost in your code:
PostCommentController is VC1
NewsViewController is VC2
So
@IBAction func unwindToViewController1(_ sender: UIStoryboardSegue) {
print("I just unwind")
}must be in VC1 PostCommentController, not in VC2 NewsViewController
In VC2, you have
func commentButtonTapped(at index: IndexPath) {
let vc = storyboard?.instantiateViewController(withIdentifier: "PostCommentController") as? PostCommentController
self.present(vc!, animated: true, completion: nil)So, you instanciate a new VC1 !
So could you also explai in simple words the logic:
- in PostCommentController: you have several posts ? Each with a like button ? What actions are possible for user ?
- in NewsViewController, what do you have ? What actions are possible for user ?
So what should I do instead of instanciate?
in PostCommentController it's the post itself after you press on the index row.
in NewsViewController you have a several posts, you have a like\unlike button,
and a comment button which is:
func commentButtonTapped(at index: IndexPath)and it takes you to PostCommentController,
there you have the same functions as like\unlike button, and a comment section,
which is irrelevent for now.
So what should I do instead of instanciate?
Do you understand why it is a problem with the drawing I posted ?
You should try dismissing the NewsViewController controller instead
TMI below/above. Let's first identify the problem here. You wrote:
"the user has a name called Bill,
.....another view ....change his name to Jack,
when Im going back to the previous view to see his name..."
The issue is what the code understands as "his name". In each view controller there is a local variable that represents "his name". They are different in the different view controllers. When you change that local variable in that second view controller you are not changing that local variable in the first view controller. So your question is really - how do I change the value of a variable in a first view controller from within a second view controller. There are many ways. The best is to use MVC structures and have only one "his name". You can do that with a singleton Model, or just use NSUserDefaults as your Model until you learn how to really follow MVC structure. Set a value for
NSString *hisName = [[NSUserDefaults standardUserDefaults] objectForKey:@"HisName"];
using
[[NSUserDefaults standardUserDefaults] setObject:@"Bill" forKey:@"HisName"];
in any view controller. Then reset it to "Jack" in any other view controller. And if you use that Model value for "HisName" as a local variable in any view controller then set the local variable each time the view controller does a viewWillAppear.