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Variadic Views
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import SwiftUI | |
struct MyValue: _ViewTraitKey { | |
static var defaultValue: Int = 0 | |
} | |
extension View { | |
func myValue(_ value: Int) -> some View { | |
_trait(MyValue.self, value) | |
} | |
} | |
struct ContentView: View { | |
var subviews: some View { | |
ForEach(0..<5) { ix in | |
Text("Hello \(ix)") | |
.myValue(ix) | |
} | |
} | |
var body: some View { | |
VStack { | |
VStack { | |
subviews.intersperse(Divider()) | |
} | |
HStack { | |
subviews.reduce { v1, v2 in | |
// Render the views backwards with dividers in between | |
v2 | |
Divider() | |
v1 | |
} | |
} | |
HStack { | |
subviews.filter { $0[MyValue.self].isMultiple(of: 2) } | |
} | |
.padding() | |
} | |
} | |
} | |
struct ContentView_Previews: PreviewProvider { | |
static var previews: some View { | |
ContentView() | |
} | |
} |
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import Foundation | |
import SwiftUI | |
extension View { | |
func filter(_ condition: @escaping (_VariadicView.Children.Element) -> Bool) -> some View { | |
variadic { children in | |
ForEach(children) { child in | |
if condition(child) { | |
child | |
} | |
} | |
} | |
} | |
} |
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import Foundation | |
import SwiftUI | |
extension View { | |
func intersperse<V: View>(_ divider: V) -> some View { | |
variadic { children in | |
if let c = children.first { | |
c | |
ForEach(children.dropFirst(1)) { child in | |
divider | |
child | |
} | |
} | |
} | |
} | |
} |
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import SwiftUI | |
extension View { | |
func reduce<R: View>(@ViewBuilder _ combine: @escaping (AnyView, AnyView) -> R) -> some View { | |
variadic { children in | |
if let c = children.first { | |
children.dropFirst(1).reduce(AnyView(c), { l, r in | |
AnyView(combine(l, AnyView(r))) | |
}) | |
} | |
} | |
} | |
} |
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import SwiftUI | |
extension View { | |
func variadic<R: View>(@ViewBuilder process: @escaping (_VariadicView.Children) -> R) -> some View { | |
modifier(VariadicModifier(helper: Helper(process: process))) | |
} | |
} | |
fileprivate struct VariadicModifier<R: View>: ViewModifier { | |
var helper: Helper<R> | |
func body(content: Content) -> some View { | |
_VariadicView.Tree(helper) { | |
content | |
} | |
} | |
} | |
fileprivate struct Helper<Result: View>: _VariadicView_MultiViewRoot { | |
var process: (_VariadicView.Children) -> Result | |
func body(children: _VariadicView.Children) -> some View { | |
process(children) | |
} | |
} | |
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