How can I access to TupleView through ViewBuilder in SwiftUI? - swiftui

Question

I am trying to get access to my TupleView which my ViewBuilder use it to build the content, then I am trying to count it, here I made my codes until this point, I need help to find the count of my TupleView, right now for unknown reason it returns 0, which I was expecting 5! thanks for help.
import SwiftUI
struct ContentView: View {
var body: some View {
ModelView(content: {
Text("Hello, world! 1")
.padding()
Text("Hello, world! 2")
.padding()
Text("Hello, world! 3")
.padding()
Text("Hello, world! 4")
.padding()
Text("Hello, world! 5")
.padding()
})
}
}
struct ModelView<Content: View>: View {
var content: () -> Content
init(#ViewBuilder content: #escaping () -> Content) {
self.content = content
let size = Mirror(reflecting: content).children.count // <<: Here! it returns 0! which must be 5!
print(size)
}
var body: some View {
content()
}
}

Answer 1

How can I access to TupleView through ViewBuilder in SwiftUI?
Explicitly to the same way as SwiftUI does. Let's see what is buildBlock of the ViewBuilder:
That means that ViewBuilder has explicit function for every count of content views from 1 to 10. Like
extension ViewBuilder {
public static func buildBlock<C0, C1, C2, C3>(_ c0: C0, _ c1: C1, _ c2: C2, _ c3: C3) -> TupleView<(C0, C1, C2, C3)> where C0 : View, C1 : View, C2 : View, C3 : View
}
So if you want to access view builder tuple views, you need to do the same, like (tested with Xcode 12.4)
struct ModelContentView: View {
var body: some View {
ModelView(content: {
Text("Hello, world! 1")
.padding()
Text("Hello, world! 2")
.padding()
// Text("Hello, world! 3")
// .padding()
// Text("Hello, world! 4")
// .padding()
// Text("Hello, world! 5")
// .padding()
})
}
}
struct ModelView<Content: View>: View {
var count: Int
var content: () -> Content
private init(count: Int = 1, #ViewBuilder content: #escaping () -> Content) {
self.content = content
self.count = count
}
var body: some View {
content()
}
}
extension ModelView {
init<V1: View, V2: View>(#ViewBuilder content: #escaping () -> Content) where Content == TupleView<(V1, V2)> {
self.init(count: 2, content: content)
}
init<V1: View, V2: View, V3: View>(#ViewBuilder content: #escaping () -> Content) where Content == TupleView<(V1, V2, V3)> {
self.init(count: 3, content: content)
}
// ... all other variants
}

Answer 2

First, by accessing Mirror(reflecting: content) you're reflecting the closure that creates Content (you can see that content is actually a closure of type () -> Content).
You probably meant to reflect the view itself. For this you need to reflect the specific instance:
let mirror = Mirror(reflecting: content()) // add the parentheses
Then you tried to access the children. If you access it using the mirror above, you'll get (type formatted for clarity):
AnyCollection<(label: Optional, value: Any)>(
_box: Swift._RandomAccessCollectionBox<
Swift.LazyMapSequence<
Swift.Range<Swift.Int>,
(label: Swift.Optional<Swift.String>, value: Any)
>
>
)
Theoretically, you could then access the value of the first key (with the label value):
if let value = Mirror(reflecting: content()).children.first?.value {
print(value)
}
You'd get the result:
(
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>(
content: SwiftUI.Text(
storage: SwiftUI.Text.Storage.anyTextStorage(
SwiftUI.unknown context at $7fff57642368.LocalizedTextStorage
), modifiers: []
),
modifier: SwiftUI._PaddingLayout(
edges: SwiftUI.Edge.Set(rawValue: 15),
insets: nil
)
),
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>(...)
)
which is a tuple of type:
(
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>,
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>,
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>,
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>,
SwiftUI.ModifiedContent<SwiftUI.Text, SwiftUI._PaddingLayout>
)
This is probably all you can get through reflection here.
Important note
From documentation:
Mirrors are used by playgrounds and the debugger.
You shouldn't probably use it in the real app.