AddingPowerSwiftUI

An extensional package for SwiftUI, which adds some missing APIs like a parsable ViewBuilder.

Status

Still in development. Documentation will be added. Currently APNavigationView fully uses APViewBuilder for the root view. APStackNavigationViewStyle uses view transfer and APStyle. There is an example project showing some basic usage.

Motivation

SwiftUI is an awesome framework that uses simple and clean declarative programming paradigms. However, it's closed source framework and we do not have the full control to the underlying functionality. This makes it hard to create clean APIs like the original. For example, when creating a container view like this:

APTabView {
    View1()
    View2()
    View3()
}

we found that no public APIs can be used to parse the view TupleView<(View1, View2, View3)>. On the contrast, primitive types like ZStack and NavigationView use _VariadicView.Tree to manage the structure inside the SwiftUI framework. The SwiftUI.swiftmodule/arm64.swiftinterface file shows more details about the hidden public APIs.

Therefore, this package aims to achieve following requirements to make APViewBuilder behave like native APIs:

• able to handle any input type like TupleView<(Text, Image)> and TupleView<(View1, View2, View3)>
• allow conditional statements like if and switch
• high efficiency. We don't want everything becomes AnyView or views get updated for unrelated changes. Only modified content needs update.

The main trick is the type erasing by UIHostingView<V> -> UIViewController and wrapping the it into a struct to pass through the view hierarchy. As a result, we only install a View or UIViewController once. Later, it updates itself without any addtional work. In other word, monitor a view in its original decleared place but use it anywhere we want.

A final result like this should work properly.

@APViewBuilder var demoView: some APView {
    Text("First Item")
    if #available(iOS 14.0, *) {
        Text("IOS 14")
    }
    APGroup {
        Text("0")
        if isOne {
            Text("1")
        }
        else {
            Text("2")
            if isThree {
                Text("3")
                
            } else {
                Text("4")
            }
        }
    }
    APForEach(0..<2) {
        if shouldShowContent {
            Text("\($0)")
        }
        Divider()
    }
    Color.green
}

This package tries to reimplement some native APIs like NavigationView and TabView to discover all the need. Some handy APIs like view transfer are provided. (Sometimes we declear an view in some place but we don't want to use it right there, for example,.tabItem(). Therefore, we would like to transfer it like other preference content).

In all, AddingPowerSwiftUI is created to provide more control for developers to SwiftUI framework.