Deinit not called where blocks used in swift 3.0

Question

I have used blocks in cell for getting switch value but now my problem is that deinit not called where i used the blocks. it is completely working previously but in swift 3.0 it is not working.

My switch cell :

import UIKit

class CellSwitch: UITableViewCell {

    @IBOutlet weak var objSwitch: UISwitch!
    @IBOutlet weak var btnInfo: UIButton!
    @IBOutlet weak var lblTitle: UILabel!
    var blockSwitch_Change : ((_ isOn:Bool) -> Void)!
    var blockBtn_Clicked : (() -> Void)!

    override func awakeFromNib() {
        super.awakeFromNib()
        self.lblTitle.font = Font.init(Font.FontType.custom(Font.FontName.NotoSans_Regular), size: Font.FontSize.standard(Font.StandardSize.Regular)).instance
        // Initialization code
    }
    //MARK:- switch object change
    @IBAction func switch_ValChanged(_ obj:UISwitch){
        self.blockSwitch_Change?(obj.isOn)
    }

    //MARK:-  button clicked
    @IBAction func btnInfo_Clicked(_ sender: UIButton) {
        self.blockBtn_Clicked?()
    }
    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

}

Uses of this cell

let cell = tableView.dequeueReusableCell(withIdentifier: CellSwitch.identifier) as? CellSwitch
                cell?.lblTitle.textColor = Color.custom(hexString: objModel.titleLblColor, alpha: 1.0).value
                cell?.lblTitle.text = objModel.strTitle
                cell?.objSwitch.isOn = objModel.isOn
                cell?.btnInfo.isHidden = !objModel.isInfoBtn
                cell?.blockBtn_Clicked = { 
                   print("button clicked")
                }
                cell?.blockSwitch_Change = { (isOn) in
                    print("switch value changed \(isOn)")
                }
                if objModel.isEnable == false
                {
                    cell?.isUserInteractionEnabled = false
                    cell?.contentView.alpha = 0.5
                }
                else
                {
                    cell?.isUserInteractionEnabled = true
                    cell?.contentView.alpha = 1.0
                }
                return cell!

Also if i comment this two blocks then my deinit will called.

Are those print statements what you always have inside the blocks the code your actually using when you see the issue? — Aidan Malone, Jul 10 '18 at 10:54
@AidanMalone no i cannot share actual code that's why i temporary put the print statement — Chirag Shah, Jul 10 '18 at 11:01
Ok, is the code inside the blocks referencing the cell itself? — Aidan Malone, Jul 10 '18 at 11:02
@AidanMalone no it there are some calculation has happened then i store the value in model of vc — Chirag Shah, Jul 10 '18 at 11:03
Ok, so it you may be creating a retain cycle with the vc itself then where you are referencing the vc inside the block. You will instead need to use a weak reference as @RakeshaShastri suggested. I'll post a code suggestion below. — Aidan Malone, Jul 10 '18 at 11:05
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/174713/discussion-between-chirag-shah-and-aidan-malone). — Chirag Shah, Jul 10 '18 at 11:05

score 3 · Accepted Answer · answered Jul 10 '18 at 11:08

It sounds like you are creating a retain cycle by referencing the view controller strongly inside the blocks. Instead you should create a weak reference to the vc to use. This is my preferred method

cell?.blockBtn_Clicked = { [weak self]
    print("button clicked")
    self?.viewModel.//do something
}
cell?.blockSwitch_Change = { [weak self] (isOn) in
    print("switch value changed \(isOn)")
    self?.viewModel.//do something
}

The [weak self] portion will pass a weak reference of self into the block, although note this reference is now an optional. You can then use optional chaining or unwrap it after that.

As an alternative you can also use [unowned self]. This will also create a weak reference, but it won't be an optional (It will be implicitly unwrapped before being passed into the block). If your unsure weak is typically safer as it protects from a potential crash, but its worth considering as perhaps you may not want the app to continue execution in the scenario where this block is called and the view controller has been removed from memory. — Aidan Malone, Jul 10 '18 at 11:18

Deinit not called where blocks used in swift 3.0

1 Answers1