UIView 크기만큼 미리보기 제공

CompactPreview.swift

/// UIView  크기만큼 미리보기 제공 

import SwiftUI

public struct CompactPreview<V: UIView>: View {
    @State private var parentSize: CGSize?
    @State private var foundSize: CGSize?
    /// UIView 빌더 
    let builder: () -> V
    /// 가로를 상위에 채울껀지 
    let fillingWidth: Bool
    
    public init(parentSize: CGSize? = nil, fillParent: Bool = true, builder: @escaping () -> V) {
        self.parentSize = parentSize
        self.fillingWidth = fillParent
        self.builder = builder
    }
    
    public var body: some View {
        ZStack {
            if let parentWidth = parentSize?.width {
                CompactUIWrapper(width: parentWidth, fillWidth: fillingWidth, sizeUpdate: { size in
                    DispatchQueue.main.async {
                        self.foundSize = size
                    }
                }, builder: builder)
            }
        }
        .frame(maxWidth: foundSize?.width ?? parentSize?.width ?? .infinity,
               maxHeight: foundSize?.height ?? parentSize?.height ?? .infinity) // 크기 제한 ..
        .background(
            GeometryReader { geometry in
                Color.clear.onAppear {
                    if foundSize != nil { return }
                    DispatchQueue.main.async {
                        parentSize = geometry.size // 상위 크기 구하기...
                    }
                }
            }
        )
    }
}

struct CompactUIWrapper<V: UIView>: UIViewRepresentable {
    var width: CGFloat
    var fillWidth: Bool
    var sizeUpdate: (CGSize) -> Void
    let builder: () -> V
    
    public func makeUIView(context: Context) -> some UIView {
        let view = builder()
        view.translatesAutoresizingMaskIntoConstraints = false
        // 적합한 크기 계산 
        let size = view.systemLayoutSizeFitting(CGSize(width: width, height: UIView.layoutFittingCompressedSize.height))
        debugPrint("CompactUIWrapper \(width) => \(size)")
        self.sizeUpdate(CGSize(width: fillWidth ? width : size.width, height: size.height))
        // 크기 설정 
        let h = view.heightAnchor.constraint(equalToConstant: size.height)
        h.priority = .defaultHigh
        h.isActive = true
        let w = view.widthAnchor.constraint(equalToConstant: fillWidth ? width : size.width)
        w.priority = .defaultHigh
        w.isActive = true
        view.setContentCompressionResistancePriority(.required, for: .vertical)
        view.setContentHuggingPriority(.required, for: .vertical)
        return view
    }
    
    public func updateUIView(_ uiView: UIViewType, context: Context) {
    }
}