如何在Swift中正确使用#selector？

Question

I'm adding a reload button for iOS in-app web browser using WKWebView.reload
I tried two options, and the two options works for me the same but I want to know what is the technical correct option to use with #selector. Is it #selector(class.method) or #selector (object.method) ?

Here is the first:

let webView = WKWebView()
view = webView
navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .refresh, target: webView, action: #selector(WKWebView.reload))

and here the second one:

let webView = WKWebView()
view = webView
navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .refresh, target: webView, action: #selector(webView)) 

Here is the full code

import UIKit
import WebKit

class ViewController: UIViewController {

    let webView = WKWebView()

    override func loadView() {
        view = webView
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .refresh, target: webView, action: #selector(WKWebView.reload))
    }
}

Answer 1

Your let webView = WKWebView() is creating a new instance of yours.. it won't work independently of your #selector

try it out:

func reloadWebView() {
    webView.reload()
}

your call:

navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .refresh, target: self, action: #selector(MyViewController.reloadWebView))

Answer 2

The function reload is not declared as @objc , therefore, it won't work as selector in swift. You may want to create a function in your ViewController and call the reload function from there.

@objc func reloadWebView() {
    webView.reload()
}

and your selector will look like this #selector(reloadWebView)

Source: https://developer.apple.com/documentation/webkit/wkwebview/1414969-reload

Answer 3

Currently, my recommendation is using #selector(target.method) .

When you pass self as target then, #selector(self.method) , passing webView to target , then #selector(webView.method) .

#selector is just an encoded ObjC method name (which does not include class name), so both #selector(ClassName.method) and #selector(object.method) should work. But you can expect a better compile-time diagnostic with #selector(target.method) .