NavigationSplitViewStyle protocol in SwiftUI

什么是NavigationSplitViewStyle

NavigationSplitViewStyle is a protocol in SwiftUI.

A type that specifies the appearance and interaction of navigation split views within a view hierarchy.

SwiftUI是如何定义的

@available(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
public protocol NavigationSplitViewStyle {
/// A view that represents the body of a navigation split view.
associatedtype Body : View
  
/// Creates a view that represents the body of a navigation split view.
///
/// SwiftUI calls this method for each instance of ``NavigationSplitView``
/// where this style is the current ``NavigaitonSplitViewStyle``.
///
/// - Parameter configuration: The properties of the instance to create.
@ViewBuilder func makeBody(configuration: Self.Configuration) -> Self.Body
  
/// The properties of a navigation split view instances.
typealias Configuration = NavigaitonSplitViewStyleConfiguration
}

SwiftUI如何调用

首先，SwiftUI会给 View这个协议进行扩展，给其添加一个方法

extension View {
  /// Sets the style for navigation split views within this view.
  ///
  /// - Parameter style: The style to set.
  ///
  /// - Returns: A view that uses the specified navigation split view style.
  @avaiable(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
  public func navigationSplitViewStyle<S>(_ style: S) -> some View where S : NavigationSplitViewStyle

}

这个方法名叫navigationSplitViewStyle ,会向其传入一个参数 style，这个style会遵循上面定义的NavigationSplitViewStyle 协议，同时SwiftUI也给我们定义了几种Style。

@available(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
extension NavigationSplitViewStyle where Self == BalancedNavigationSplitViewStyle {

    /// A navigation split style that reduces the size of the detail content
    /// to make room when showing the leading column or columns.
    public static var balanced: BalancedNavigationSplitViewStyle { get }
}

@available(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
extension NavigationSplitViewStyle where Self == ProminentDetailNavigationSplitViewStyle {

    /// A navigation split style that attempts to maintain the size of the
    /// detail content when hiding or showing the leading columns.
    public static var prominentDetail: ProminentDetailNavigationSplitViewStyle { get }
}

@available(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
extension NavigationSplitViewStyle where Self == AutomaticNavigationSplitViewStyle {

    /// A navigation split style that resolves its appearance automatically
    /// based on the current context.
    public static var automatic: AutomaticNavigationSplitViewStyle { get }
}