pagerkit/references/PKPageBuilder.md

PKPageBuilder

PKPageBuilder is a result builder that allows you to declaratively construct a list of PKPage components for a PKPagesView.

Overview

You don't use PKPageBuilder directly. Instead, it's the technology that powers the closure-based syntax of PKPagesView. It allows you to mix and match different ways of creating pages in a natural, SwiftUI-like way.

Features

PKPageBuilder supports:

• Multiple pages: Simply list your PKPage views.
• Conditional pages: Use if and if-else statements.
• Optional pages: Use if let to include pages based on optional data.
• Platform-specific pages: Use #if or if #available.
• Pages from arrays: ForEach is also supported through the builder.

Examples

Mixing Static and Conditional Pages

struct ContentView: View {
    @State private var showExtraPage = true

    var body: some View {
        PKPagesView {
            PKPage { Text("Welcome") }

            if showExtraPage {
                PKPage { Text("An Extra Page") }
            }

            if #available(iOS 16.0, *) {
                PKPage { Text("This page is only for iOS 16+") }
            } else {
                PKPage { Text("This is a fallback for older iOS versions") }
            }
        }
    }
}

Pages from a ForEach

PKPageBuilder works with ForEach to dynamically generate pages from a collection.

struct ContentView: View {
    let items = ["First", "Second", "Third"]

    var body: some View {
        PKPagesView {
            ForEach(items, id: \.self) { item in
                PKPage { Text("Page: \(item)") }
            }
        }
    }
}

How It Works

PKPageBuilder has a set of static methods that the Swift compiler uses to transform the declarative code inside the PKPagesView closure into a single array of PKPage objects. These methods include:

• buildBlock(...): Combines multiple pages into one list.
• buildEither(first:) and buildEither(second:): Handles if-else statements.
• buildOptional(_:): Handles if let.
• buildLimitedAvailability(_:): Handles #available checks.
• buildExpression(_:): Handles a single page expression.

You don't need to call these methods yourself; the compiler does it for you.