📱 Master–Detail Template, Drill-Down Menus & Navigation (iOS – Xcode)

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✅ 1. Definition

🔹 Master–Detail Template

A Master–Detail app is a common iOS design pattern where:

• Master View → shows a list of items
• Detail View → shows full information about the selected item

👉 Example:

• Email app (Inbox → Email content)
• Contacts app (List → Contact details)

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🔹 Drill-Down Menu

A drill-down menu is a navigation style where the user:

• Starts from a list (main screen)
• Taps an item
• Moves deeper into another screen with more details

👉 It creates a hierarchical navigation flow

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🔹 Navigation

Navigation is the process of moving between different screens (View Controllers) using:

• Navigation Controller
• Segues
• Push / Pop transitions

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🧠 2. Key Concepts

🔹 UINavigationController

• Manages a stack of view controllers
• Controls navigation flow

🔹 Navigation Stack

• First screen = root view controller
• New screens are pushed on top

Root → Screen 1 → Screen 2 → Screen 3

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🔹 Push & Pop

Action	Meaning
Push	Move to next screen
Pop	Go back to previous screen

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🏗️ 3. Master–Detail Structure

Master View (List)
        ↓
   User selects item
        ↓
Detail View (Information)

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⚙️ 4. How Master–Detail Works

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🔹 Step 1: Master View (Table View)

• Displays list of items
• Uses UITableView

let items = ["iPhone", "iPad", "MacBook"]

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🔹 Step 2: Select Item

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let selectedItem = items[indexPath.row]
}

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🔹 Step 3: Navigate to Detail View

Using Storyboard Segue:

• Control + Drag → “Show (Push)”

OR programmatically:

let vc = storyboard?.instantiateViewController(withIdentifier: "DetailVC") as! DetailViewController
vc.selectedItem = items[indexPath.row]
navigationController?.pushViewController(vc, animated: true)

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🔹 Step 4: Display Detail Data

override func viewDidLoad() {
    super.viewDidLoad()
    
    detailLabel.text = selectedItem
}

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🔄 5. Drill-Down Navigation Flow

List Screen
   ↓ tap
Category Screen
   ↓ tap
Detail Screen

👉 Each selection goes deeper into the app structure.

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📊 6. Diagram Description (for Exams)

Draw:

Master (List)
    ↓
Detail (Info)
    ↓
More Detail (Optional Drill Down)

OR Navigation Stack:

Root → Screen 1 → Screen 2 → Screen 3

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🧭 7. Navigation Methods in iOS

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🔹 1. Push Navigation

navigationController?.pushViewController(vc, animated: true)

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🔹 2. Pop Navigation

navigationController?.popViewController(animated: true)

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🔹 3. Pop to Root

navigationController?.popToRootViewController(animated: true)

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💡 8. Example App

🎯 Product App

• Master: Product list
• Detail: Product information

Flow:

1. User selects “iPhone”
2. Moves to detail screen
3. Shows specs, price, description

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📌 9. Important Rules / Tips

• Always embed in Navigation Controller
• Use segues or push navigation
• Pass data before navigating
• Maintain clean hierarchy
• Use drill-down only for related screens

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⚠️ 10. Common Mistakes

• ❌ Not using Navigation Controller
• ❌ Forgetting to pass data to detail view
• ❌ Wrong storyboard identifiers
• ❌ Losing navigation stack
• ❌ Overcomplicated navigation flow

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🧠 11. Best Practices

• Keep master list simple
• Use clear navigation hierarchy
• Pass only necessary data
• Use reusable view controllers
• Maintain consistent UI flow

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📝 12. Likely Exam Questions

1. What is a Master–Detail application?
2. Explain drill-down navigation.
3. What is UINavigationController?
4. Differentiate push and pop navigation.
5. How do you pass data between view controllers?
6. Explain navigation stack with diagram.
7. Write code to navigate to detail screen.
8. What is the use of Master view in iOS apps?

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📚 13. Quick Revision Summary

• Master View → list of items

• Detail View → selected item info

• Drill-down → step-by-step deeper navigation

• Uses:

  • Navigation Controller
  • Push / Pop methods

• Navigation stack manages screens

• Very common in:

  • Settings apps
  • Email apps
  • Product catalogs

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