SwiftUI-AnySubviews

SwiftUI-AnySubviews backports iOS 18's subview accessing API to iOS 13, providing a unified API to consistently interact with subviews across different iOS versions.

On iOS 18, SwiftUI introduces a new API Group(subviews:transform:) to allow developers to access the subviews of a given content view. This API is only available for iOS 18. However, there is an API called VariadicView exists since the first release of SwiftUI, which has almost the same feature with Group(subviews:transform:). SwiftUI-AnySubViews unifies these two API so developers can use a consistent API across different iOS versions.

You can check VariadicView's detail on The Moving Parts Team's blog SwiftUI under the Hood: Variadic Views.

Requirements

• Xcode 16 (Swift 6.0)
• iOS 13, macOS 10.15, tvOS 13, watchOS 6, visionOS 1 or later

Installation

Use Swift Package Manager to add this package.

https://github.com/Lumisilk/SwiftUI-AnySubviews.git

If you use SwiftUI-AnySubviews in another package, add this line to your dependencies.

.product(name: "AnySubviews", package: "SwiftUI-AnySubviews")

Usage

You can use BackportGroup basiclly like using Group(subviews:transform:).

Check the official documents for further usage.

import AnySubviews

struct CardsView<Content: View>: View {
    
    var content: Content
    
    init(@ViewBuilder content: () -> Content) {
        self.content = content()
    }
    
    var body: some View {
        VStack {
            BackportGroup(subviews: content) { subviews in
                HStack {
                    if subviews.count >= 2 {
                        SecondaryCard { subview[1] }
                    }
                    if let first = subviews.first {
                        FeatureCard { first }
                    }
                    if subviews.count >= 3 {
                        SecondaryCard { subviews[2] }
                    }
                }
                if subviews.count > 3 {
                    subviews[3...]
                }
            }
        }
    }
}

Types

SwiftUI-AnySubViews unifies the following types, ensuring consistent API usage across different iOS versions:

AnySubViews	iOS 18 API	below iOS 18
AnySubview	Subview	_VariadicView_Children.Element
AnySubviewsCollection	SubviewsCollection	_VariadicView_Children
AnySubviewsCollectionSlice	SubviewsCollectionSlice	Slice<_VariadicView_Children>
AnyContainerValues	ContainerValues	_ViewTraitKey

ContainerValues

ContainerValues is also supported in AnySubviews. To define your custom container values associated with a view, use macro AnyEntry within AnyContainerValueKeys's extension:

// Define
extension AnyContainerValueKeys {
//  #AnyEntry<Type>(keyName, defaultValue)
    #AnyEntry<Int>("myNumber", 0)
    #AnyEntry<String>("myName", "Name")
}

// Set
someView
    .anyContainerValue(keyPath: \.myNumber, 1)
    .anyContainerValue(keyPath: \.myName, "Lumi")

// Read
BackportGroup(subviews: content) { subviews in
    ForEach(subviews) { subview in
        let number = subview.containerValues.myNumber.description
        let name = subview.containerValues.myName
        Text(number + " " + name)
    }
}

Dropping iOS 17

When your app no longer needs to support iOS 17 and earlier versions, you can simplify your codebase:

1. Remove the SwiftUI-AnySubviews package from your project completely.
2. Replace all occurrences of BackportGroup with Group throughout your codebase.
3. For ContainerValues especially:
   1. Replace definition part with official API extension ContainerValues { @Entry ... }.
   2. Replace setting part with official API .containerValue(key: MyKey.self, value: 2).
   3. Reaplce reading part with official API subview.containerValues.myCustomValue.

Note: Only proceed with this step when you're certain that your app's minimum supported iOS version is 18 or later.

TODO

• Enrich the error desecription of Macro AnyEntry
• Add a realistic view example using Anysubviews

Contributing

Contributions are welcome! Please feel free to submit a Issue or Pull Request.

License

SwiftUI-AnySubViews is released under the MIT license. See LICENSE for details.