SwiftUI helpers

helpers.swift

struct <#MyView#>: View {
    var body: some View {
        <#body#>
    }
}

extension View {
    func geometryPreference<P: PreferenceKey>(_ key: P.Type, value: @escaping (GeometryProxy) -> P.Value) -> some View {
        overlay(GeometryReader { proxy in
            Color.clear.preference(key: P.self, value: value(proxy))
        })
    }
}

struct Preference<P: PreferenceKey, Content: View>: View where P.Value: Equatable {
    let content: (P.Value) -> Content
    @State private var value: P.Value = P.defaultValue
    
    init(_ key: P.Type, @ViewBuilder content: @escaping (P.Value) -> Content) {
        self.content = content
    }
    
    var body: some View {
        content(value)
            .onPreferenceChange(P.self) { self.value = $0 }
    }
}