So I have TableViewCell's that are being populated from 2 Dicitionaries in my view controller.
var categories : [Int : [String : Any]]!
var assignments : [Int: [String : Any]]!
I have a UiTextField in my cell that the user is supposed to be able to edit. I then want to be able to change the values of certain keys in that dictionary-based off what the user changes and re-display the table with those changes. My main problem is that I don't know how I will be able to access theese variables from within my cell. I have a method in my view controller that takes the row that the text field is in, along with the value of the textField, and updates the dictionaries. What I need is to be able to instantiate the view controller that the cell is in but I need the original instance that already has values loaded into the categories and assignments Dictionaries. If you have any other ideas on how I could accomplish this please post.
You can use delegate for sharing cell-data to your VC:
protocol YourCellDelegate() {
func pickedString(str: String)
}
class YourCell: UITableViewCell {
var delegate: YourCellDelegate! = nil
#IBOutlet weak var textField: UITextField!
.....//some set-method, where you can handle a text
func textHandle() {
guard let del = delegate else { return }
del.pickedString(textField.text)
}
.....
}
And usage in your VC: When you create cell, set its delegate self:
...
cell.delegate = self
...
and sure you VC supported your Delegate Protocol:
class YourVC: UIViewController, YourCellDelegate {
}
And now, you MUST implement protocol method:
class YourVC: UIViewController, YourCellDelegate {
....
func pickedString(str: String) {
}
....
}
All times, when you use textHandle() in your cell, pickedString(str: String) activates in yourVC with string from textField.
Enjoy!
Related
I needed to delegate a click action for my UIView class to my UIViewController class since Swift does not support multiple class inheritance. So i wanted it such that once a button is clicked on my subview, a function in my BrowserViewController class is called.
I am using a protocol to achieve this, but on the function does not triggered when the button is tapped. Please help me out.
View Controller
class BrowseViewController: UIViewController {
var categoryItem: CategoryItem! = CategoryItem() //Category Item
private func setupExplore() {
//assign delegate of category item to controller
self.categoryItem.delegate = self
}
}
// delegate function to be called
extension BrowseViewController: ExploreDelegate {
func categoryClicked(category: ProductCategory) {
print("clicked")
let categoryView = ProductByCategoryView()
categoryView.category = category
categoryView.modalPresentationStyle = .overCurrentContext
self.navigationController?.pushViewController(categoryView, animated: true)
}
}
Explore.swift (subview)
import UIKit
protocol ExploreDelegate: UIViewController {
func categoryClicked(category: ProductCategory)
}
class Explore: UIView {
var delegate: ExploreDelegate?
class CategoryItem: UIView {
var delegate: ExploreDelegate?
var category: ProductCategory? {
didSet {
self.configure()
}
}
var tapped: ((_ category: ProductCategory?) -> Void)?
func configure() {
self.layer.cornerRadius = 6
self.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(self.categoryTapped)))
self.layoutIfNeeded()
}
#objc func categoryTapped(_ sender: UIGestureRecognizer) {
delegate?.categoryClicked(category: ProductCategory.everything)
self.tapped?(self.category)
}
}
}
Simply add a print statement inside categoryTapped.
You will then know if it is actually being tapped.
A million things could go wrong, for example, you may have forget to set the UIView to allow intertaction.
After checking that. Next add another print statement inside categoryTapped which shows you whether or not the delegate variable is null.
You'll quickly discover the problem using simple print statements.
print("I got to here!")
It's that easy.
And what about
if delegate == nil { print("it is nil!! oh no!" }
else { print("phew. it is NOT nil.") }
Debugging is really that easy at this level.
Next add a print statement inside setupExplore()
func setupExplore() {
print("setup explore was called")
....
See what happens.
I don't see any piece of code which sets the delegate.
First of all, define delegate as a property inside CategoryItem class, Then you must set the current instance of BrowseViewController to the delegate variable of CategoryItem. Now you can expect your method being called.
There are a few things that could cause the delegate method to not be triggered in this code:
Ensure that isUserInteractionEnabled = true on your CategoryItem. This is probably best done in either the configure() function in the CategoryItem or in the setupExplore() function of the BrowseViewController.
Make sure that the setupExplore() function on the BrowseViewController is being called, and that the category is being set on the CategoryItem to trigger the configure function. Otherwise, either the delegate or the gesture recognizer might not being set.
Side Note - weak vs strong delegate
On a side note, it is usually best practice to make your delegate properties weak var rather that having them be a strong reference, as this makes them prone to strong retain cycles.
Therefore, you might want to consider making the var delegate: ExploreDelegate? on your CategoryItem into weak var delegate: ExploreDelegate?. For more information on this problem, view this post.
this should be straight forward but i m finding hard time in understanding.
i have a class
class Field:NSObject {
var name:String?
var answer:String?
.................
}
Now i also have a viewcontroller in which there is a tableview. I am using Field array as datasource for this tableview. i am passing relavent object from Field array to my custom cell class (see below) which have a UItextfield .
cell.field = self.fields[indexPath.row]
What i want is that when text inside UItextfield is changed this should update our main Field array. Also custom cell class should have fresh copy of Field instance. I hope i have made it clear, please ask if you didn't understand anything. Much obliged.
here is cell class code
class SpeechCell: UITableViewCell, UITextFieldDelegate {
public var field:Field?{
didSet{
self.lblField.text = self.field?.name
self.txtAnswer.placeholder = self.field?.name
}
}
func textFieldDidEndEditing(_ textField: UITextField, reason: UITextFieldDidEndEditingReason) {
self.field?.answer = textField.text!
self.commandDelegate?.didUpdateField(field: self.field!, textField: textField)
}
override func prepareForReuse() {
self.txtAnswer.text = self.field?.answer
}
here is code for tableview
func didUpdateField(field: Field, textField: UITextField) {
self.fields[textField.tag].answer = textField.text!
}
You should use custom delegate method to notify the view controller about the changes in the textfield. In the custom delegate method you should update the fields array. You should change the field in the cell too before calling the custom delegate method.
You should call this delegate method in the textFieldDidChangeText.
I am relatively new on firebase. I want to update existing data on my firebase database. I have UITableView and UITableViewCells on my Xcode project, when user touch (tap gesture), for example a outlet on cell view, I want to update Firebase Database but this could be any cell on tableview. How to find this cell which user touched on screen, on firebase database and update its messageVoteScore value. There are assigned keys but my cells do not know those keys,
I could not figure it out how to match them.(Database/Messages/{"sender": "email"},{"messageBody":"text.."},{"messageVoteScore":"100"}
#objc func voteUpTapped(sender: UITapGestureRecognizer) {
// Update score //
self.messageVoteScore.text = String(Int(self.messageVoteScore.text!)! + 1 )
//observeSingleEventOfType listens for a tap by the current user.
Database.database().reference().child("Messages").observe(.value){
(snapshot) in
if let snapshotValue = snapshot.value as? [String : String] {
print(snapshotValue)
}
}
}
Are you passing class objects to your cell? If so you could use a protocol/delegate for this. A UITableView Cell is a View and shouldn't function as a controller. your UITableViewController should be updating firebase.
you should start by adding something like this to the top of your Cell class:
protocol MyTableViewCellDelegate: class {
func thingDidDo(object: Object, text: String...) //object is the class object you are changing.
then add the delegate to your properties:
weak var delegate: MyTableViewCellDelegate?
then add the IBAction:
#IBAction func thingDidDo(_ sender: Any) {
delegate?.thingDidDo(object: object, text: textView.text...)
}
Now back to your viewController Class:
In your "cellForRowAt" write in the delegate:
cell.delegate = self
then add an extension
extension MyTableViewController: MyTableViewCellDelegate {
func thingDidDo(object: Object, text: String) {
Do whatever you want with object, text...
}
Not sure what kind of function you are trying to perform so I made this as generic as I could
I have a UICollectionView with a CollectionReusableView header. I want to pass a string from the collecitonview to the header, so that the header knows which data to load based on the string. I am trying to use delegates/protocols to do this, but keep getting "unexpectedly found nil while unwrapping an optional value." Here is my code:
protocol UserToQuery {
func thisUser(x: String)
}
class Profile: UICollectionViewController {
var ownProfile = true
var delegate:UserToQuery?
override func viewDidLoad() {
super.viewDidLoad()
if self.ownProfile == true {
let username = PFUser.currentUser()?.username
self.delegate!.thisUser(username!)
}
}
}
And here is the code for the Header view:
class ProfileHeader: UICollectionReusableView, UserToQuery {
var id1 = String()
var controller = Profile()
override func awakeFromNib() {
print(id1)
controller.delegate? = self
}
func thisUser(x: String) {
self.id1 = x
getProfileInfo()
}
func getUserData() {
// code here uses the id1 value to get data
}
}
My understanding of delegates/protocols is this: if you want to pass data (i.e., string), to another view, you make the view that receives the string conform to a protocol. This protocol includes a function that is used to pass the string, and when that function is called, it notifies the other view that the string is now available for use, and then you code what you want and use the string. Is that accurate?
In ProfileHeader, you have a variable, controller, which is creating a new instance of Profile, which is NOT the Profile view controller from your storyboard. This is why self.delegate! is nil in Profile.viewDidLoad().
I am going to make the assumption that ProfileHeader is a view in the Profile view controller. In your viewDidLoad, you should set the delegate to the ProfileHeader. See the example code below (I assume an outlet for the ProfileHeader view):
EDIT: ProfileHeader is not an outlet, as mentioned in the comments. Updated my answer to reflect that.
class Profile: UICollectionViewController {
var ownProfile = true
var delegate:UserToQuery?
override func viewDidLoad() {
super.viewDidLoad()
// Set the delegate!
self.delegate = ProfileHeader()
if self.ownProfile == true {
let username = PFUser.currentUser()?.username
// Delegate won't be nil now
self.delegate!.thisUser(username!)
}
}
}
}
As a general flow, the view controller should keep references to the view, not the other way around. So remove the controller property from your ProfileHeader view. The view shouldn't care what view controller is controlling it.
You have some misunderstandings about protocol/delegate, but it’s normal when you start iOS development.
First of all, why does the app crash :
The variable delegate is an optional UserQuery. It’s okay for a delegate to be optional, but it’s never set in your code, so when you call :
self.delegate!.thisUser(username!)
you try to force unwrapping a nil variable, which results in the crash.
Protocols
Now, let’s talk about the protocol/delegate relationship.
You have an UICollectionViewController subclass, which embeds an UICollectionView object. This UICollectionView will be contains a mix of header, footer and cell. Your ProfileHeader class will thus be displayed within your UICollectionView.
In order to populate an UICollectionView, you don’t need to create your own protocol : there are already two protocols for this :
UICollectionViewDataSource is the main protocol to conforms to, because it allows you to populate the collection view
UICollectionViewDelegate is used for further customization of your tableview, i.e. customizing the appearance and handling events.
Since your Profile class inherits from UICollectionViewControlleryou don’t have to named these protocols after your class name since UICollectionViewController already conforms to these protocols as written in Apple docs
You will have to override the delegate and protocol methods in order to display some data. My advice is, before using headers and footers, to use only UICollectionViewCell objects for start easily.
By overriding the method -collectionView:numberOfItemsInSection: and - collectionView:cellForItemAtIndexPath:, you will be able to populate the collection view.
All of the searches I've done focus on passing data between view controllers. That's not really what I'm trying to do. I have a ViewController that has multiple Views in it. The ViewController has a slider which works fine:
var throttleSetting = Float()
#IBAction func changeThrottleSetting(sender: UISlider)
{
throttleSetting = sender.value
}
Then, in one of the Views contained in that same ViewController, I have a basic line that (for now) sets an initial value which is used later in the DrawRect portion of the code:
var RPMPointerAngle: CGFloat {
var angle: CGFloat = 2.0
return angle
}
What I want to do is have the slider's value from the ViewController be passed to the View contained in the ViewController to allow the drawRect to be dynamic.
Thanks for your help!
EDIT: Sorry, when I created this answer I was having ViewControllers in mind. A much easier way would be to create a method in SomeView and talk directly to it.
Example:
class MainViewController: UIViewController {
var view1: SomeView!
var view2: SomeView!
override func viewDidLoad() {
super.viewDidLoad()
// Create the views here
view1 = SomeView()
view2 = SomeView()
view.addSubview(view1)
view.addSubview(view2)
}
#IBAction func someAction(sender: UIButton) {
view1.changeString("blabla")
}
}
class SomeView: UIView {
var someString: String?
func changeString(someText: String) {
someString = someText
}
}
Delegate:
First you create a protocol:
protocol NameOfDelegate: class { // ": class" isn't mandatory, but it is when you want to set the delegate property to weak
func someFunction() // this function has to be implemented in your MainViewController so it can access the properties and other methods in there
}
In your Views you have to add:
class SomeView: UIView, NameOfDelegate {
// your code
func someFunction() {
// change your slider settings
}
}
And the last step, you'll have to add a property of the delegate, so you can "talk" to it. Personally I imagine this property to be a gate of some sort, between the two classes so they can talk to each other.
class MainViewController: UIViewController {
weak var delegate: NameOfDelegate?
#IBAction func button(sender: UIButton) {
if delegate != nil {
let someString = delegate.someFunction()
}
}
}
I used a button here just to show how you could use the delegate. Just replace it with your slider to change the properties of your Views
EDIT: One thing I forgot to mention is, you'll somehow need to assign SomeView as the delegate. But like I said, I don't know how you're creating the views etc so I can't help you with that.
In the MVC model views can't communicate directly with each other.
There is always a view controller who manages the views. The views are just like the controllers minions.
All communication goes via a view controller.
If you want to react to some view changing, you can setup an IBAction. In the method you can then change your other view to which you might have an IBOutlet.
So in your example you might have an IBAction for the slider changing it's value (as in your original question) from which you could set some public properties on the view you would like to change. If necessary you could also call setNeedsDisplay() on the target view to make it redraw itself.