Introspect underlying UIKit components from SwiftUI

Introspect for SwiftUI

Introspect allows you to get the underlying UIKit or AppKit element of a SwiftUI view.

For instance, with Introspect you can access UITableView to modify separators, or UINavigationController to customize the tab bar.

How it works

Introspect works by adding a custom IntrospectionView to the view hierarchy, then looking into the UIKit hierarchy to find the relevant view.

For instance, when introspecting a TextField, it will:

Add IntrospectionView as an overlay of TextField
Get the view host of the introspection view (which is alongside the view host of the UITextField)
Get the previous sibling containing UITextField

Please note that this introspection method might break in future SwiftUI releases. Future implementations might not use the same hierarchy, or might not use UIKit elements that are being looked for. Though the library is unlikely to crash, the .introspect() method will not be called in those cases.

Usage in production

Introspect is meant to be used in production. It does not use any private API. It only inspects the view hierarchy using publicly available methods. The library takes a defensive approach to inspecting the view hierarchy: there is no hard assumption that elements are laid out a certain way, there is no force-cast to UIKit classes, and the introspect() methods are simply ignored if UIKit views cannot be found.

Install

SwiftPM

https://github.com/siteline/SwiftUI-Introspect.git

Cocoapods

pod "Introspect"

Introspection

Implemented

SwiftUI	UIKit	AppKit	Introspect
List	UITableView	NSTableView	`.introspectTableView()`
ScrollView	UIScrollView	NSScrollView	`.introspectScrollView()`
NavigationView	UINavigationController	N/A	`.introspectNavigationController()`
Any embedded view	UIViewController	N/A	`.introspectViewController()`
TabView	UITabBarController	N/A	`.introspectTabBarController()`
TextField	UITextField	NSTextField	`.introspectTextField()`
Toggle	UISwitch	N/A	`.introspectSwitch()`
Slider	UISlider	NSSlider	`.introspectSlider()`
Stepper	UIStepper	NSStepper	`.introspectStepper()`
DatePicker	UIDatePicker	NSDatePicker	`.introspectDatePicker()`
Picker (SegmentedPickerStyle)	UISegmentedControl	NSSegmentedControl	`.introspectSegmentedControl()`

Missing an element? Please create an issue. As a temporary solution, you can implement your own selector.

Cannot implement

SwiftUI	Why
Text	Not a UILabel
Image	Not a UIImageView
Button	Not a UIButton

Examples

List

List {
    Text("Item 1")
    Text("Item 2")
}
.introspectTableView { tableView in
    tableView.separatorStyle = .none
}

ScrollView

ScrollView {
    Text("Item 2")
}
.introspectScrollView { scrollView in
    scrollView.refreshControl = UIRefreshControl()
}

NavigationView

NavigationView {
    Text("Item 2")
    .introspectNavigationController { navigationController in
        navigationController.navigationBar.backgroundColor = .red
    }
}

TextField

TextField("Text Field", text: $textFieldValue)
.introspectTextField { textField in
    textField.layer.backgroundColor = UIColor.red.cgColor
}

Implement your own selector

Missing an element? Please create an issue.

In case Introspect doesn't support the SwiftUI element that you're looking for, you can implement your own selector. For example, to look for a UITextField:

extension View {
    public func introspectTextField(customize: @escaping (UITextField) -> ()) -> some View {
        return inject(IntrospectionView(
            selector: { introspectionView in
                guard let viewHost = Introspect.findViewHost(from: introspectionView) else {
                    return nil
                }
                return Introspect.previousSibling(containing: UITextField.self, from: viewHost)
            },
            customize: customize
        ))
    }
}

You can use any of the following methods to inspect the hierarchy:

Introspect.findChild(ofType:in:)
Introspect.previousSibling(containing:from:)
Introspect.nextSibling(containing:from:)
Introspect.findAncestor(ofType:from:)
Introspect.findHostingView(from:)
Introspect.findViewHost(from:)

Releasing

Increment version number:

$ bundle exec fastlane run increment_version_number bump_type:minor # major|minor|patch

Update changelog with new version
Bump version in Introspect.podspec
Commit and push changes
Tag new version:

$ git tag -a <VERSION> -m "<MESSAGE>"
$ git push origin --tags

Push to cocoapods trunk:

$ bundle exec pod trunk push .