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Building a WebView for iOS and macOS in SwiftUI

Apr 24, 2022  ·  swiftuiopen-sourcemulti-platform

Since SwiftUI currently has no WebView, we have to create one ourselves. Let’s see how easy it is to build a multi-platform web view for iOS, iPadOS & macOS.

One way to achieve this is to wrap native, platform-specific views in UIViewRepresentable for UIKit and an NSViewRepresentable for AppKit.

The big question is then, which view do we want our representable to wrap? We have two native web browser components to consider: WKWebView and SFSafariViewController.

WKWebView

WebKit provides us with an WKWebView, which is a powerful web browser component that supports both iOS & macOS.

To wrap this view, we need to handle both UIKit and AppKit. We can do this by defining a typealias for the view representable type, to make the rest of the code cleaner:

#if os(iOS)
typealias WebViewRepresentable = UIViewRepresentable
#elseif os(macOS)
typealias WebViewRepresentable = NSViewRepresentable
#endif

We can now begin. First import the required frameworks. We need SwiftUI and WebKit:

import SwiftUI
import WebKit

We can then define our view. Let’s call it WebView and let it implement ViewRepresentable:

public struct WebView: WebViewRepresentable {
    ...
}

Add two initializers - one that takes a non-optional URL and one that takes an optional URL and a WKWebView configuration block:

public init(url: URL) {
    self.url = url
    self.configuration = { _ in }
}

public init(
    url: URL? = nil,
    configuration: @escaping (WKWebView) -> Void = { _ in }) {
    self.url = url
    self.configuration = configuration
}

private let url: URL?
private let configuration: (WKWebView) -> Void

We can now create a web view that loads a url or configures itself with a configuration (to setup delegates etc.), then loads the url if we provide it with one.

This gives us full flexibility - either a simple, url-based setup or a more configurable one.

For iOS, we have to implement makeUIView and updateUIView:

#if os(iOS)
public func makeUIView(context: Context) -> WKWebView {
    makeView()
}

public func updateUIView(_ uiView: WKWebView, context: Context) {}
#endif

For macOS, we have to implement makeNSView and updateNSView:

#if os(macOS)
public func makeNSView(context: Context) -> WKWebView {
    makeView()
}

public func updateNSView(_ view: WKWebView, context: Context) {}
#endif

Since both platforms setup WKWebView in the same way, we can define a single function:

private extension WebView {
    
    func makeView() -> WKWebView {
        let view = WKWebView()
        configuration(view)
        tryLoad(url, into: view)
        return view
    }

    func tryLoad(_ url: URL?, into view: WKWebView) {
        guard let url = url else { return }
        view.load(URLRequest(url: url))
    }
}

That’s it! We now have a WebView that can be used on both iOS and macOS.

Let’s take a look at the slightly different SFSafariViewController.

SFSafariViewController

SFSafariViewController is defined in SafariServices. It displays a navigation bar topmost and a toolbar bottommost, with action buttons for navigation, reload, etc.

SFSafariViewController only supports iOS, so we must use an OS check when using it:

#if os(iOS)
....
#endif

Let’s start. First import the required frameworks. We need SwiftUI and SafariServices:

import SwiftUI
import SafariServices

We can then define our view. Let’s call it SafariWebView. Since we only support iOS, it just have to implement UIViewControllerRepresentable:

public struct SafariWebView: UIViewControllerRepresentable {
    ...
}

Notice that we implement UIViewControllerRepresentable instead of UIViewRepresentable, since the embedded type is a view controller and not a view.

Since, SFSafariViewController can be created with a url and configuration, let’s adjust the approach from above to let you inject both a configuration and a viewConfiguration.

public init(
    url: URL,
    configuration: SFSafariViewController.Configuration = .init(),
    viewConfiguration: @escaping (SFSafariViewController) -> Void = { _ in }) {
    self.url = url
    self.configuration = configuration
    self.viewConfiguration = viewConfiguration
}

private let url: URL
private let configuration: SFSafariViewController.Configuration
private let viewConfiguration: (SFSafariViewController) -> Void

We can then implement makeUIViewController and updateUIViewController:

public func makeUIViewController(context: Context) -> SFSafariViewController {
    let controller = SFSafariViewController(url: url, configuration: configuration)
    viewConfiguration(controller)
    return controller
}

public func updateUIViewController(_ safariViewController: SFSafariViewController, context: Context) {}

The configuration is used to craete the view and the view configuration is used to configure the created view.

That’s it! We now have a SafariWebView that can be used on iOS and iPadOS.

Conclusion

You’ve seen two ways to create a web view for SwiftUI. I wouldn’t be surprised if Apple will add such a view at this year’s WWDC. Until they do, I hope that this helps.

I have added the source code and a demo app to a tiny SDK called WebViewKit. Feel free to check it out and let me know what you think.

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