📱 Using Property Lists (Plist) for Data Persistence & Creating Multi-Section Tables (iOS – Xcode)

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✅ 1. Definition

🔹 Property List (plist)

A Property List (plist) is a file used in iOS to store structured data in key–value format. It is commonly used for simple data persistence.

👉 It stores data like:

• Arrays
• Dictionaries
• Strings, Numbers, Booleans

📌 File extension: .plist

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🔹 Data Persistence

Data persistence means saving data so it remains available even after the app is closed and reopened.

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🔹 Multi-Section Table

A UITableView with multiple sections, where data is grouped into categories.

👉 Example:

• Fruits section
• Vegetables section
• Drinks section

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🧠 2. Key Concepts

🔹 Plist Structure

A plist can be:

• Dictionary-based
• Array-based

Example structure:

Food
 ├── Fruits
 ├── Vegetables
 └── Drinks

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🔹 Table Sections

A table view contains:

• Sections (groups)
• Rows (items inside each section)

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💾 3. Using Property List for Data Persistence

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🔹 Step 1: Create a plist file

• File → New → Property List
• Name it: data.plist

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🔹 Step 2: Add Data

Example plist structure:

Fruits → Apple, Banana, Mango  
Vegetables → Carrot, Potato  
Drinks → Water, Juice

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🔹 Step 3: Read Data from plist

if let path = Bundle.main.path(forResource: "data", ofType: "plist"),
   let dict = NSDictionary(contentsOfFile: path) as? [String: [String]] {
    
    print(dict)
}

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🔹 Step 4: Store Data in Arrays

var sections: [String] = []
var data: [[String]] = []

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🔹 Step 5: Load Data

sections = Array(dict.keys)
data = Array(dict.values)

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📊 4. Multi-Section UITableView

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🔹 Step 1: Number of Sections

func numberOfSections(in tableView: UITableView) -> Int {
    return sections.count
}

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🔹 Step 2: Number of Rows per Section

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return data[section].count
}

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🔹 Step 3: Cell Content

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = UITableViewCell(style: .default, reuseIdentifier: "cell")
    
    cell.textLabel?.text = data[indexPath.section][indexPath.row]
    
    return cell
}

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🔹 Step 4: Section Title

func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
    return sections[section]
}

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📊 5. Diagram Description (for Exams)

Draw:

TableView
 ├── Fruits
 │     ├ Apple
 │     ├ Banana
 │
 ├── Vegetables
 │     ├ Carrot
 │     ├ Potato
 │
 └── Drinks
       ├ Water
       ├ Juice

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💡 6. Example App

🎯 Grocery App

• Sections:

  • Fruits
  • Vegetables
  • Drinks

👉 Data stored in plist 👉 Displayed in multi-section table

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📌 7. Important Rules / Tips

• Plist is good for small static data only
• Use dictionaries for section-based data
• Always reload table after loading data
• Keep data structured (key-value or arrays)
• Use section titles for better UI

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⚠️ 8. Common Mistakes

• ❌ Using plist for large data (not recommended)
• ❌ Wrong data casting from plist
• ❌ Not matching section and row data
• ❌ Forgetting to reload table view
• ❌ Incorrect indexing (section/row mismatch)

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🧠 9. Best Practices

• Use plist for:

  • Settings
  • Static lists

• Use JSON/Core Data for large apps

• Keep data organized in dictionaries

• Always validate data before use

• Use meaningful section names

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📝 10. Likely Exam Questions

1. What is a Property List (plist)?
2. How is data stored in plist files?
3. What is data persistence in iOS?
4. Explain multi-section table view.
5. Write code to load data from plist.
6. How do you define number of sections in UITableView?
7. What is titleForHeaderInSection used for?
8. Differentiate between plist and database storage.

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📚 11. Quick Revision Summary

• Plist = key-value file for storing small data

• Used for data persistence

• Multi-section table groups data into categories

• Key methods:

  • numberOfSections
  • numberOfRowsInSection
  • cellForRowAt

• Section titles improve UI clarity

• Best for static data (settings, lists)

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