Lecture Notes: Saving Data in iOS Apps with SQLite

Introduction to SQLite

• SQLite is a simple SQL database used in iOS apps to save data.
• Queries are written in Swift to persist data to disk.
• Data can be read back when users reopen the app.

Basic SQL Queries in SQLite

• CREATE Query: Creates tables

  • Example: CREATE TABLE users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT)
  • id is an INTEGER, PRIMARY KEY, AUTOINCREMENT.
  • name is a TEXT field for user names.

• INSERT Query: Inserts data into tables

  • Example: INSERT INTO users (name) VALUES ('Tommy')

• SELECT Query: Reads data from tables

  • Example: SELECT * FROM users WHERE name = 'Tommy'

• UPDATE Query: Updates existing data in tables

  • Example: UPDATE users SET name = 'Tommy M' WHERE name = 'Tommy'

Example App: Notes App

• Simple Notes App to create, read, save, and browse notes using SQLite.

Setting Up Xcode Project

1. Create a new Xcode project named 'Notes'.
2. Use the storyboard to set up the initial views.
   • Use a TableViewController for the main screen showing notes.
   • Use a second ViewController for the note detail view.
3. Embed a Navigation Controller.
4. Customize the table view cells and navigation.

Creating the Model

1. Define a Note Struct
   • struct Note { var id: Int, var contents: String }
2. Create NoteManager Class
   • Manages database connections, reads, updates, and creates notes.

Connecting to SQLite

1. Database Path Setup
   • Use FileManager to get the database URL.
   • Ensure the database file and its directory exist.
2. Database Connection
   • Use sqlite3_open to connect.
3. Creating Tables
   • Use sqlite3_exec to execute SQL commands.

CRUD Operations

1. Create Note
   • Prepare and execute INSERT statement, bind parameters.
2. Get All Notes
   • Prepare and execute SELECT statement, read data in a loop.
3. Save Note
   • Prepare and execute UPDATE statement, bind parameters.

Integrating Model with ViewControllers

1. Passing Data
   • Use prepare(for:sender:) to pass data between view controllers.
2. Reload Data on Return
   • Use viewWillAppear to refresh data when returning to the main view.
3. Editing and Saving Notes
   • Handle text view data binding and call save methods on note updates.

Adding User Interface Elements

• Add UI elements like buttons, text views, and labels.
• Set up constraints for UI elements to fit different screen sizes.

Final Testing

• Run the app to ensure notes are created, saved, and displayed correctly.