Grid layout (LazyVGrid, LazyHGrid) in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

How many items are visible in this LazyVGrid?

Consider this SwiftUI code snippet that creates a vertical grid with fixed columns:

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

var body: some View {
  ScrollView {
    LazyVGrid(columns: columns) {
      ForEach(0..<5) { index in
        Rectangle()
          .frame(height: 50)
          .overlay(Text("Item \(index)"))
      }
    }
  }
}

How many grid items will be shown in one full row?

iOS Swift

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

var body: some View {
  ScrollView {
    LazyVGrid(columns: columns) {
      ForEach(0..<5) { index in
        Rectangle()
          .frame(height: 50)
          .overlay(Text("Item \(index)"))
      }
    }
  }
}

A 2

B 1

C 5

D 10

💡 Hint

Count how many columns are defined in the columns array.

The LazyVGrid uses the columns array to define how many columns appear per row. Here, there are 2 columns, so each row shows 2 items.

❓ ui_behavior

intermediate

What happens if you use LazyHGrid with one fixed row?

Given this SwiftUI code:

let rows = [GridItem(.fixed(80))]

var body: some View {
  ScrollView(.horizontal) {
    LazyHGrid(rows: rows) {
      ForEach(0..<4) { index in
        Circle()
          .frame(width: 60, height: 60)
          .overlay(Text("\(index)"))
      }
    }
  }
}

What is the layout behavior of the circles?

iOS Swift

let rows = [GridItem(.fixed(80))]

var body: some View {
  ScrollView(.horizontal) {
    LazyHGrid(rows: rows) {
      ForEach(0..<4) { index in
        Circle()
          .frame(width: 60, height: 60)
          .overlay(Text("\(index)"))
      }
    }
  }
}

A Circles are arranged vertically in a single column, scrollable up and down.

B Circles are arranged in a grid with 4 rows and 1 column.

C Circles overlap each other in the same position.

D Circles are arranged horizontally in a single row, scrollable sideways.

💡 Hint

LazyHGrid arranges items horizontally along rows.

LazyHGrid with one fixed row arranges items side by side horizontally in that row. The ScrollView(.horizontal) allows sideways scrolling if needed.

🧠 Conceptual

advanced

What is the effect of using .adaptive GridItem in LazyVGrid?

In SwiftUI, you can define grid columns like this:

let columns = [GridItem(.adaptive(minimum: 80))]

What does the .adaptive option do in a LazyVGrid?

iOS Swift

let columns = [GridItem(.adaptive(minimum: 80))]

var body: some View {
  LazyVGrid(columns: columns) {
    ForEach(0..<10) { index in
      Rectangle()
        .frame(height: 50)
        .overlay(Text("Item \(index)"))
    }
  }
}

A It fixes the grid to exactly one column of 80 points width.

B It creates as many columns as fit horizontally with at least 80 points width each.

C It creates columns that automatically resize to fill the entire screen width.

D It creates a grid with a fixed number of columns equal to 80.

💡 Hint

Think about how many columns can fit if each column is at least 80 points wide.

The .adaptive option creates as many columns as possible that are at least the minimum width. This makes the grid flexible and responsive.

❓ lifecycle

advanced

When are views inside LazyVGrid created and destroyed?

In SwiftUI, LazyVGrid creates views lazily. What does this mean for the lifecycle of the views inside the grid?

A Views are created only when they appear on screen and destroyed when scrolled off screen.

B All views are created immediately when the grid appears and stay in memory.

C Views are created randomly regardless of visibility.

D Views are created once and never destroyed even if off screen.

💡 Hint

Lazy means views are made only when needed.

LazyVGrid creates views only when they are about to appear on screen, saving memory and improving performance. Views off screen can be destroyed.

🔧 Debug

expert

Why does this LazyVGrid code cause a runtime crash?

Examine this SwiftUI code:

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

var body: some View {
  ScrollView {
    LazyVGrid(columns: columns) {
      ForEach(0..<3) { index in
        Text("Item \(index)")
          .frame(width: 150, height: 50)
          .background(Color.blue)
      }
    }
  }
}

When running, the app crashes with a layout constraint error. Why?

iOS Swift

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

var body: some View {
  ScrollView {
    LazyVGrid(columns: columns) {
      ForEach(0..<3) { index in
        Text("Item \(index)")
          .frame(width: 150, height: 50)
          .background(Color.blue)
      }
    }
  }
}

A Text views cannot have background colors inside LazyVGrid.

B ForEach range is too small to fill the grid, causing a crash.

C The fixed column width (100) conflicts with the child frame width (150), causing layout errors.

D ScrollView must be horizontal for LazyVGrid to work.

💡 Hint

Check if child views fit inside the fixed column widths.

The columns are fixed at 100 points wide, but the child views request 150 points width, which conflicts and causes a runtime layout crash.