Swift3：Delegate函数未运行

Question

I'm building an app where I start at a TableViewController and when I click on a cell it will go to another viewcontroller and run a function that I created in the new viewcontroller. I'm currently using protocols and delegate but even after following along tutorials and guides I find online I am still not able to get the function to run.

Here's my tableview controller code. I included the code that I thought relevant.

class interestPTableViewController: BaseViewController, UITableViewDataSource, UITableViewDelegate {

        var ipSearchDelegate: IPSearch?

        public func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {       
                ipSearchDelegate?.ipZoom()
        }
}

Heres my other viewcontroller code. I cannot get it to print "hello"

protocol IPSearch: class{
      func ipZoom()
}

class searchMapViewController: BaseViewController{
      override func viewDidLoad(){
            let ipip = storyboard!.instantiateViewController(withIdentifier: "interestP") as! interestPTableViewController
            ipip.ipSearchDelegate = self
      }
}
extension searchMapViewController: IPSearch {
      func ipZoom(){
           print("hello")
      }
}

Any help will be nice. Thanks in advance.

Answer 1

Try in this way, you should keep instance of your VC:

    class searchMapViewController: BaseViewController{
      var ipip: interestPTableViewController! // <- This is important part

      override func viewDidLoad(){
            ipip = storyboard!.instantiateViewController(withIdentifier: "interestP") as! interestPTableViewController
            ipip.ipSearchDelegate = self
      }
}

Answer 2

Your SearchMapViewController's viewDidLoad is instantiating a new InterestPTableViewController and setting its delegate and then discarding it. That newly created view controller will be deallocated as soon as your viewDidLoad exits. The time to set the delegate is in prepareForSegue

.

Answer 3

Make your first VC conform to your protocol

 class interestPTableViewController: BaseViewController, UITableViewDataSource, UITableViewDelegate, IPSearch {

        var ipSearchDelegate: IPSearch?

        public func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {       
                ipSearchDelegate?.ipZoom()
        }
}

Answer 4

Here is how your task is done in the "conventional" Protocol / Delegate pattern.

This is the "map view" controller...

//
//  SearchMapViewController.swift
//

import UIKit

protocol IPSearch: class{
    func ipZoom()
}

extension SearchMapViewController: IPSearch {
    func ipZoom(){
        print("hello")
    }
}

class SearchMapViewController: BaseViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    // MARK: - Navigation

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        // assuming another button (hamburger menu?) is triggering a segue
        // to the "table view" controller, this is where you
        // assign the delegate

        if let vc = segue.destination as? InterestPViewController {
            vc.delegate = self
        }

    }

}

This is the View with a Table of rows to select from...

//
//  InterestPViewController.swift
//

import UIKit

class InterestPViewController: BaseViewController, UITableViewDelegate, UITableViewDataSource {

    var delegate: IPSearch?

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    // MARK: - Table view data source

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 15
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "basicCell", for: indexPath)

        cell.textLabel?.text = "\(indexPath)"

        return cell
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        // just print so we know we've tapped a row
        print("row selected", indexPath.row)

        // call a func in the "map view" - likely, ipZoom() will be changed to
        // something along the lines of ipZoom(selectedRow: indexPath.row)
        delegate?.ipZoom()

        // returning to the "map view"

        // either
        self.navigationController?.popViewController(animated: true)

        // or
        //presentingViewController?.dismiss(animated: true, completion: nil)

    }

}