Protocol Not Working

Question

Created Jan ’21

Replies 19

Boosts 0

Views 1.2k

Participants 3

I'm trying to transfer a tableview cell from my hockeydetailVC to my favouritesVC using a button and I can't transfer it due to some issue.

My hockeydetailVC

Code Block protocol addThis {
  func addFav(data: CurrentPlayers)
}

I'm trying to transfer my item object

Code Block var item: CurrentPlayers?  
 
var delegate: addThis? = nil

Code Block func sendData() {
    if delegate != nil {
      let data = item!
      delegate?.addFav(data: data)
      print("This is the data being transferred: \(data)")
    }
  }
   
  @IBAction func addToFav(_ sender: Any) {
    sendData()
    print("Favourite button Pressed")
  }

My favouritesVC

Code Block  var currentFav: CurrentPlayers?

Code Block func addFav(data: CurrentPlayers) {
    currentFav = data
  }

I have a segue for my button so I have this

Code Block   override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  if segue.identifier == "r" {
    let hockeyDetailVC: HockeyDetailVC = segue.destination as! HockeyDetailVC
    hockeyDetailVC.delegate = self
  }
 }

If the transfer works then my sendData() method up top would print a statement but my addToFav only prints "favourite button pressed".

Answered by ZoneX in 660866022

I'm going to close this thread.

Boost

Answer 1

OOPer OP

Jan ’21

If the transfer works then my sendData() method up top would print a statement but my addToFav only prints "favourite button pressed".

Then I guess delegate is nil when sendData() is called.

By the way, please follow the simple coding rule of Swift -- type names should start with Capital letter.
Your code is hard to read.

0

Answer 2

Claude31 OP

Jan ’21

You just post thumbnail views of your code, it is impossible to guess where the problem is.

Does your class conform to the AddThis protocol ?

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Answer 3

ZoneX OP

Jan ’21

Yeah my class conforms to the protocol addThis class favouritesVC: UITableViewController, addThis . I intialized my delegate to not be nil and it still does not show the print statement from sendData.

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Answer 4

OOPer OP

Jan ’21

I intialized my delegate to not be nil

Hidden parts of your code may be affecting. For example, The actual instance of the view controller running sendData() may not be the same instance you initialized.

If you could show enough code, we would not need such guess game.

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Answer 5

Claude31 OP

Jan ’21

The question is how you initialize the destination controller.

I intialized my delegate to not be nil

probably not.
As explained, you may set the delegate on an instance and then create and use another one somewhere.

Add this print to confirm:

Code Block func sendData() {
    if delegate != nil {
      let data = item!
      delegate?.addFav(data: data)
      print("This is the data being transferred: \(data)")
    } else {
      print("The delegate is nil")
    }
  }

You could also check the instance:

Code Block   override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  if segue.identifier == "r" {
    let hockeyDetailVC: HockeyDetailVC = segue.destination as! HockeyDetailVC	
              // forcing with as! is dangerous; 
              // you'd better use: 
              // if let hockeyDetailVC = segue.destination as? HockeyDetailVC {
    hockeyDetailVC.delegate = self
    print("destination HockeyDetailVC is", hockeyDetailVC)
  }
 }

and in HockeyDetailVC viewDidload, add:

Code Block 	print("invoked HockeyDetailVC is", self)

Report all the results

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Answer 6

ZoneX OP

Jan ’21

Btw this is all the code related to my protocol and what I am trying to transfer. As for the data on the results

Code Block print("invoked HockeyDetailVC is", self)

gives me invoked HockeyDetailVC is <LearnHockey.HockeyDetailVC: 0x7fe0b3026200>. Can you explain the 0x7fe0b3026200.

Code Block print("The delegate is nil")

gives me The delegate is nil.

Code Block print("destination HockeyDetailVC is", hockeyDetailVC)

This does not print anything to my console.

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Answer 7

OOPer OP

Jan ’21

This does not print anything to my console.

That means the segue with identifier "r" is not triggered. Better check how you are showing HockeyDetailVC.

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Answer 8

Claude31 OP

Jan ’21

So there is a problem in prepare.

Instrument more the code:

Code Block override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  print("segue identifier", segue.identifier)
  if segue.identifier == "r" {
    let hockeyDetailVC: HockeyDetailVC = segue.destination as! HockeyDetailVC
    hockeyDetailVC.delegate = self
  }
 }

and tell what you get.
If you get something different from
segue identifier r
such as
segue identifier R
or
segue identifier SomeString
that means that "r" is not the identifier of this segue.
Then change "r" by what you got here after "segue identifier"

Note:

Code Block print("invoked HockeyDetailVC is", self)

gives me invoked HockeyDetailVC is <LearnHockey.HockeyDetailVC: 0x7fe0b3026200>. Can you explain the 0x7fe0b3026200.

0x7fe0b3026200 is simply the address o self.
The point would be to compare with the instance in HockeyDetailVC viewDidload

But the problem is most likely in prepare.

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Answer 9

ZoneX OP

Jan ’21

Okay I can't do segue.destination as? HockeyDetailVC but is (segue.destination as? HockeyDetailVC)! okay?

Code Block print("segue identifier", segue.identifier)

does not give me any response on the console.

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Answer 10

OOPer OP

Jan ’21

does not give me any response on the console.

That means prepare(for:sender:) is not called. Are you really using segue to show HockeyDetailVC?
Aren't you using present to show it?

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Answer 11

Claude31 OP

Jan ’21

Okay I can't do segue.destination as? HockeyDetailVC but is (segue.destination as? HockeyDetailVC)! okay?

Did you write

Code Block     if let hockeyDetailVC = segue.destination as? HockeyDetailVC  {
	  hockeyDetailVC.delegate = self
   }

print("segue identifier", segue.identifier)
does not give me any response on the console.

Please tell exactly how you call the segue:

by defining in IB ? If so, from where to where exactly
in code with performSegue ? If so, show the complete func where it is called

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Answer 12

ZoneX OP

Jan ’21

This is how I define the function

Code Block   override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  if segue.identifier == "r" {
    print("segue identifier", segue.identifier)
    let hockeyDetailVC: HockeyDetailVC = segue.destination as! HockeyDetailVC
    hockeyDetailVC.delegate = self
    print("destination HockeyDetailVC is", hockeyDetailVC)
  }
 }

I don't use an IB but I have an identifier I named r in the storyboard.

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Answer 13

OOPer OP

Jan ’21

I have an identifier I named r in the storyboard.

That has no meaning. Even if you have a segue with identifier r, you need to properly invoke it.

By the way, print("segue identifier", segue.identifier) needs to places outside of if-statement to explore what's happening to your project.

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Answer 14

ZoneX OP

Jan ’21

Even if I place it outside the r it still does not print I may have to do this a different way.

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Answer 15

OOPer OP

Jan ’21

Even if I place it outside the r it still does not print I may have to do this a different way.

Then it's must not may. Please share the solution if you solved it by yourself.

0