Cannot subclass WKWebView

问题

I am trying to subclass WKWebView. When I implement my own initializer, I got this error:

'required' initializer 'init(coder:)' must be provided by subclass of 'WKWebView'

Ok, that is well known that we have to implement it for subclasses of UIView. For a direct subclass of UIView it works just implementing it, but with WKWebView it does not seem so simple. I followed the Fix-it hint, and this snippet is added to the code:

required @availability(*, unavailable) convenience init!(coder: NSCoder!) {
        fatalError("init(coder:) has not been implemented")
    }

So I get a class like the following:

import WebKit


class TSWebView : WKWebView {

    let s: String
    let i: Int

    init(s: String, i: Int) {
        self.s = s
        self.i = i
        super.init(frame: CGRectZero, configuration: WKWebViewConfiguration())
    }

    required @availability(*, unavailable) convenience init!(coder: NSCoder!) {
        fatalError("init(coder:) has not been implemented")
    }
}

However, when I do this I get these four other errors:

expected declaration
    required @availability(*, unavailable) convenience init!(coder: NSCoder!) {

consecutive declarations on a line must be separated by ';'
    required @availability(*, unavailable) convenience init!(coder: NSCoder!) {

cannot override 'init' which has been marked unavailable
    required @availability(*, unavailable) convenience init!(coder: NSCoder!) {

'required' modifier must be present on all overrides of a required initializer
    required @availability(*, unavailable) convenience init!(coder: NSCoder!) {

Any ideas? My Xcode Version is 6.1.1 (6A2008a). Thanks a lot.

回答1:

This is totes possible. You must only use convenience initializers and properties with default values set:

import WebKit
class MPWebView : WKWebView {
    var transparent: Bool = false

    convenience init(config: WKWebViewConfiguration = WKWebViewConfiguration()) {
       let prefs = WKPreferences()
       prefs.plugInsEnabled = true // NPAPI for Flash, Java, Hangouts
       prefs.minimumFontSize = 14
       prefs.javaScriptCanOpenWindowsAutomatically = true;
       config.preferences = prefs
       config.suppressesIncrementalRendering = false
       self.init(frame: CGRectZero, configuration: config)
    }

    convenience required init(url: NSURL) {
       self.init(config: nil)
       loadRequest(NSURLRequest(URL: url))
    }
}

回答2:

Try taking out the extra decorations:

import WebKit

class TSWebView : WKWebView {

    let s: String
    let i: Int

    init(s: String, i: Int) {
        self.s = s
        self.i = i
        super.init(frame: CGRectZero, configuration: WKWebViewConfiguration())
    }

    convenience init!(coder: NSCoder!) {
        super.init(coder:coder)
    }
}

Although I'm guessing the whole point of the "availablity(*, unavailable)" is to make it so that you can't invoke the initializer (and hence can't effectively subclass WKWebView.

回答3:

Just override the regular initialization like this. This worked for me, Swift 5.

override init(frame: CGRect, configuration: WKWebViewConfiguration) {
    super.init(frame: frame, configuration: configuration)
}

required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

来源：https://stackoverflow.com/questions/27487821/cannot-subclass-wkwebview

标签

ios

swift

subclass

init

wkwebview