❌.readSize()

(deprecated)

SwiftUI ⟩ Views ⟩ View ⟩ .readSize()

⭐️ 注意：使用 .readSize() 有個大問題，請看： problem with .readSize().

💡 提示：此方法已改名為 .onChangeSize() 。

🌀 .readSize()

// 2022.02.15

extension View {
    /// get parent's offered size.
    /// ```
    /// view.readSize { size in ... }
    /// ```
    func readSize(onChange: @escaping (CGSize) -> Void) -> some View {
        background( GeometryReader { geo in
            Color.clear.preference(key: SizePreferenceKey.self, value: geo.size)
        }).onPreferenceChange(SizePreferenceKey.self, perform: onChange)
    }
}

private struct SizePreferenceKey: PreferenceKey {
    static var defaultValue: CGSize = .zero
    static func reduce(value: inout CGSize, nextValue: () -> CGSize) {}
}

🗣 討論

• Get width of a view using in SwiftUI

👥 相關

• use Preferences to get view's size.

• .getSize() fix the problem with .readSize().