SwiftUI Introspect

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

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

How it works

SwiftUI Introspect works by adding an invisible IntrospectionView on top of the selected view, and an invisible "anchor" view underneath it, then looking through the UIKit/AppKit view hierarchy between the two to find the relevant view.

For instance, when introspecting a ScrollView...

ScrollView {
    Text("Item 1")
}
.introspect(.scrollView, on: .iOS(.v13, .v14, .v15, .v16, .v17)) { scrollView in
    // do something with UIScrollView
}

... it will:

Add marker views in front and behind ScrollView.
Traverse through all subviews between both marker views until a UIScrollView instance (if any) is found.

Important

Although this introspection method is very solid and unlikely to break in itself, future OS releases require explicit opt-in for introspection (.iOS(.vXYZ)), given potential differences in underlying UIKit/AppKit view types between major OS versions.

By default, the .introspect modifier acts directly on its receiver. This means calling .introspect from inside the view you're trying to introspect won't have any effect. However, there are times when this is not possible or simply too inflexible, in which case you can introspect an ancestor, but you must opt into this explicitly by overriding the introspection scope:

ScrollView {
    Text("Item 1")
        .introspect(.scrollView, on: .iOS(.v13, .v14, .v15, .v16, .v17), scope: .ancestor) { scrollView in
            // do something with UIScrollView
        }
}

Usage in production

SwiftUI 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/AppKit classes, and the .introspect modifier is simply ignored if UIKit/AppKit views cannot be found.

Install

Swift Package Manager

let package = Package(
    dependencies: [
        .package(url: "https://github.com/siteline/swiftui-introspect", from: "1.0.0"),
    ],
    targets: [
        .target(name: <#Target Name#>, dependencies: [
            .product(name: "SwiftUIIntrospect", package: "swiftui-introspect"),
        ]),
    ]
)

CocoaPods

pod 'SwiftUIIntrospect', '~> 1.0'

Introspection

Implemented

Missing an element? Please start a discussion. As a temporary solution, you can implement your own introspectable view type.

Cannot implement

SwiftUI	Affected Frameworks	Why
Text	UIKit, AppKit	Not a UILabel / NSLabel
Image	UIKit, AppKit	Not a UIImageView / NSImageView
Button	UIKit	Not a UIButton

Examples

List

List {
    Text("Item")
}
.introspect(.list, on: .iOS(.v13, .v14, .v15)) { tableView in
    tableView.backgroundView = UIView()
    tableView.backgroundColor = .cyan
}
.introspect(.list, on: .iOS(.v16, .v17)) { collectionView in
    collectionView.backgroundView = UIView()
    collectionView.subviews.dropFirst(1).first?.backgroundColor = .cyan
}

ScrollView

ScrollView {
    Text("Item")
}
.introspect(.scrollView, on: .iOS(.v13, .v14, .v15, .v16, .v17)) { scrollView in
    scrollView.backgroundColor = .red
}

NavigationView

NavigationView {
    Text("Item")
}
.navigationViewStyle(.stack)
.introspect(.navigationView(style: .stack), on: .iOS(.v13, .v14, .v15, .v16, .v17)) { navigationController in
    navigationController.navigationBar.backgroundColor = .cyan
}

TextField

TextField("Text Field", text: <#Binding<String>#>)
    .introspect(.textField, on: .iOS(.v13, .v14, .v15, .v16, .v17)) { textField in
        textField.backgroundColor = .red
    }

Advanced usage

Implement your own introspectable type

Missing an element? Please start a discussion.

In case SwiftUI Introspect (unlikely) doesn't support the SwiftUI element that you're looking for, you can implement your own introspectable type.

For example, here's how the library implements the introspectable TextField type:

import SwiftUI
@_spi(Advanced) import SwiftUIIntrospect

public struct TextFieldType: IntrospectableViewType {}

extension IntrospectableViewType where Self == TextFieldType {
    public static var textField: Self { .init() }
}

#if canImport(UIKit)
extension iOSViewVersion<TextFieldType, UITextField> {
    public static let v13 = Self(for: .v13)
    public static let v14 = Self(for: .v14)
    public static let v15 = Self(for: .v15)
    public static let v16 = Self(for: .v16)
    public static let v17 = Self(for: .v17)
}

extension tvOSViewVersion<TextFieldType, UITextField> {
    public static let v13 = Self(for: .v13)
    public static let v14 = Self(for: .v14)
    public static let v15 = Self(for: .v15)
    public static let v16 = Self(for: .v16)
    public static let v17 = Self(for: .v17)
}

extension visionOSViewVersion<TextFieldType, UITextField> {
    public static let v1 = Self(for: .v1)
}
#elseif canImport(AppKit)
extension macOSViewVersion<TextFieldType, NSTextField> {
    public static let v10_15 = Self(for: .v10_15)
    public static let v11 = Self(for: .v11)
    public static let v12 = Self(for: .v12)
    public static let v13 = Self(for: .v13)
    public static let v14 = Self(for: .v14)
}
#endif

Introspect on future platform versions

By default, introspection applies per specific platform version. This is a sensible default for maximum predictability in regularly maintained codebases, but it's not always a good fit for e.g. library developers who may want to cover as many future platform versions as possible in order to provide the best chance for long-term future functionality of their library without regular maintenance.

For such cases, SwiftUI Introspect offers range-based platform version predicates behind the Advanced SPI:

import SwiftUI
@_spi(Advanced) import SwiftUIIntrospect

struct ContentView: View {
    var body: some View {
        ScrollView {
            // ...
        }
        .introspect(.scrollView, on: .iOS(.v13...)) { scrollView in
            // ...
        }
    }
}

Bear in mind this should be used cautiosly, and with full knowledge that any future OS version might break the expected introspection types unless explicitly available. For instance, if in the example above hypothetically iOS 18 stops using UIScrollView under the hood, the customization closure will never be called on said platform.

Keep instances outside the customize closure

Sometimes, you might need to keep your introspected instance around for longer than the customization closure lifetime. In such cases, @State is not a good option because it produces retain cycles. Instead, SwiftUI Introspect offers a @Weak property wrapper behind the Advanced SPI:

import SwiftUI
@_spi(Advanced) import SwiftUIIntrospect

struct ContentView: View {
    @Weak var scrollView: UIScrollView?

    var body: some View {
        ScrollView {
            // ...
        }
        .introspect(.scrollView, on: .iOS(.v13, .v14, .v15, .v16, .v17)) { scrollView in
            self.scrollView = scrollView
        }
    }
}

Community projects

Here's a list of open source libraries powered by the SwiftUI Introspect library:

If you're working on a library built on SwiftUI Introspect or know of one, feel free to submit a PR adding it to the list.

xbz77/swiftui-introspect