charleswiltgen/axiom-swiftui-containers-ref

SwiftUI Containers Reference

Stacks, grids, outlines, and scroll enhancements. iOS 14 through iOS 26.

Sources: WWDC 2020-10031, 2022-10056, 2023-10148, 2024-10144, 2025-256

Quick Decision

| Use Case | Container | iOS | |----------|-----------|-----| | Fixed views vertical/horizontal | VStack / HStack | 13+ | | Overlapping views | ZStack | 13+ | | Large scrollable list | LazyVStack / LazyHStack | 14+ | | Multi-column grid | LazyVGrid | 14+ | | Multi-row grid (horizontal) | LazyHGrid | 14+ | | Static grid, precise alignment | Grid | 16+ | | Hierarchical data (tree) | List with children: | 14+ | | Custom hierarchies | OutlineGroup | 14+ | | Show/hide content | DisclosureGroup | 14+ |

---

Part 1: Stacks

VStack, HStack, ZStack

VStack(alignment: .leading, spacing: 12) {
    Text("Title")
    Text("Subtitle")
}

HStack(alignment: .top, spacing: 8) {
    Image(systemName: "star")
    Text("Rating")
}

ZStack(alignment: .bottomTrailing) {
    Image("photo")
    Badge()
}

ZStack alignments: .center (default), .top, .bottom, .leading, .trailing, .topLeading, .topTrailing, .bottomLeading, .bottomTrailing

Spacer

HStack {
    Text("Left")
    Spacer()
    Text("Right")
}

Spacer(minLength: 20)  // Minimum size

---

LazyVStack, LazyHStack (iOS 14+)

Render children only when visible. Use inside ScrollView.

ScrollView {
    LazyVStack(spacing: 0) {
        ForEach(items) { item in
            ItemRow(item: item)
        }
    }
}

Pinned Section Headers

ScrollView {
    LazyVStack(pinnedViews: [.sectionHeaders]) {
        ForEach(sections) { section in
            Section(header: SectionHeader(section)) {
                ForEach(section.items) { item in
                    ItemRow(item: item)
                }
            }
        }
    }
}

---

Part 2: Grids

Grid (iOS 16+)

Non-lazy grid with precise alignment. Loads all views at once.

Grid(alignment: .leading, horizontalSpacing: 10, verticalSpacing: 10) {
    GridRow {
        Text("Name")
        TextField("Enter name", text: $name)
    }
    GridRow {
        Text("Email")
        TextField("Enter email", text: $email)
    }
}

Modifiers:

• gridCellColumns(_:) — Span multiple columns
• gridColumnAlignment(_:) — Override column alignment

Grid {
    GridRow {
        Text("Header").gridCellColumns(2)
    }
    GridRow {
        Text("Left")
        Text("Right").gridColumnAlignment(.trailing)
    }
}

---

LazyVGrid (iOS 14+)

Vertical-scrolling grid. Define columns; rows grow unbounded.

let columns = [
    GridItem(.flexible()),
    GridItem(.flexible()),
    GridItem(.flexible())
]

ScrollView {
    LazyVGrid(columns: columns, spacing: 16) {
        ForEach(items) { item in
            ItemCard(item: item)
        }
    }
}

LazyHGrid (iOS 14+)

Horizontal-scrolling grid. Define rows; columns grow unbounded.

let rows = [GridItem(.fixed(100)), GridItem(.fixed(100))]

ScrollView(.horizontal) {
    LazyHGrid(rows: rows, spacing: 16) {
        ForEach(items) { item in
            ItemCard(item: item)
        }
    }
}

GridItem.Size

| Size | Behavior | |------|----------| | .fixed(CGFloat) | Exact width/height | | .flexible(minimum:maximum:) | Fills space equally | | .adaptive(minimum:maximum:) | Creates as many as fit |

// Adaptive: responsive column count
let columns = [GridItem(.adaptive(minimum: 150))]

---

Part 3: Outlines

List with Hierarchical Data (iOS 14+)

struct FileItem: Identifiable {
    let id = UUID()
    var name: String
    var children: [FileItem]?  // nil = leaf
}

List(files, children: \.children) { file in
    Label(file.name, systemImage: file.children != nil ? "folder" : "doc")
}
.listStyle(.sidebar)

OutlineGroup (iOS 14+)

For custom hierarchical layouts outside List.

List {
    ForEach(canvases) { canvas in
        Section(header: Text(canvas.name)) {
            OutlineGroup(canvas.graphics, children: \.children) { graphic in
                GraphicRow(graphic: graphic)
            }
        }
    }
}

DisclosureGroup (iOS 14+)

@State private var isExpanded = false

DisclosureGroup("Advanced Options", isExpanded: $isExpanded) {
    Toggle("Enable Feature", isOn: $feature)
    Slider(value: $intensity)
}

---

Part 4: Common Patterns

Photo Grid

let columns = [GridItem(.adaptive(minimum: 100), spacing: 2)]

ScrollView {
    LazyVGrid(columns: columns, spacing: 2) {
        ForEach(photos) { photo in
            AsyncImage(url: photo.thumbnailURL) { image in
                image.resizable().aspectRatio(1, contentMode: .fill)
            } placeholder: { Color.gray }
            .aspectRatio(1, contentMode: .fill)
            .clipped()
        }
    }
}

Horizontal Carousel

ScrollView(.horizontal, showsIndicators: false) {
    LazyHStack(spacing: 16) {
        ForEach(items) { item in
            CarouselCard(item: item).frame(width: 280)
        }
    }
    .padding(.horizontal)
}

File Browser

List(selection: $selection) {
    OutlineGroup(rootItems, children: \.children) { item in
        Label {
            Text(item.name)
        } icon: {
            Image(systemName: item.children != nil ? "folder.fill" : "doc.fill")
        }
    }
}
.listStyle(.sidebar)

---

Part 5: Performance

When to Use Lazy

| Size | Scrollable? | Use | |------|-------------|-----| | 1-20 | No | VStack/HStack | | 1-20 | Yes | VStack/HStack in ScrollView | | 20-100 | Yes | LazyVStack/LazyHStack | | 100+ | Yes | LazyVStack/LazyHStack or List | | Grid <50 | No | Grid | | Grid 50+ | Yes | LazyVGrid/LazyHGrid |

Cache GridItem arrays — define outside body:

struct ContentView: View {
    let columns = [GridItem(.adaptive(minimum: 150))]  // ✅
    var body: some View {
        LazyVGrid(columns: columns) { ... }
    }
}

iOS 26 Performance

• 6x faster list loading for 100k+ items
• 16x faster list updates
• Reduced dropped frames in scrolling
• Nested ScrollViews with lazy stacks now properly defer loading:

ScrollView(.horizontal) {
    LazyHStack {
        ForEach(photoSets) { set in
            ScrollView(.vertical) {
                LazyVStack {
                    ForEach(set.photos) { PhotoView(photo: $0) }
                }
            }
        }
    }
}

---

Part 6: Scroll Enhancements

containerRelativeFrame (iOS 17+)

Size views relative to scroll container.

ScrollView(.horizontal) {
    LazyHStack {
        ForEach(cards) { card in
            CardView(card: card)
                .containerRelativeFrame(.horizontal, count: 3, span: 1, spacing: 16)
        }
    }
}

scrollTargetLayout (iOS 17+)

Enable snapping.

ScrollView(.horizontal) {
    LazyHStack {
        ForEach(items) { ItemCard(item: $0) }
    }
    .scrollTargetLayout()
}
.scrollTargetBehavior(.viewAligned)

scrollPosition (iOS 17+)

Track topmost visible item. Requires .id() on each item.

@State private var position: Item.ID?

ScrollView {
    LazyVStack {
        ForEach(items) { item in
            ItemRow(item: item).id(item.id)
        }
    }
}
.scrollPosition(id: $position)

scrollTransition (iOS 17+)

.scrollTransition { content, phase in
    content
        .opacity(1 - abs(phase.value) * 0.5)
        .scaleEffect(phase.isIdentity ? 1.0 : 0.75)
}

onScrollGeometryChange (iOS 18+)

.onScrollGeometryChange(for: Bool.self) { geo in
    geo.contentOffset.y < geo.contentInsets.top
} action: { _, isTop in
    showBackButton = !isTop
}

onScrollVisibilityChange (iOS 18+)

VideoPlayer(player: player)
    .onScrollVisibilityChange(threshold: 0.2) { visible in
        visible ? player.play() : player.pause()
    }

---

Resources

WWDC: 2020-10031, 2022-10056, 2023-10148, 2024-10144, 2025-256

Docs: /swiftui/lazyvstack, /swiftui/lazyvgrid, /swiftui/lazyhgrid, /swiftui/grid, /swiftui/outlinegroup, /swiftui/disclosuregroup

Skills: axiom-swiftui-layout, axiom-swiftui-layout-ref, axiom-swiftui-nav, axiom-swiftui-26-ref