Lecture 13: Persistence

TL;DR

Learn how to store and manage data in iOS apps using Persistence, including UserDefaults, Codable and JSON, UIDocument, Core Data, CloudKit, and the file system.

Transcript

(enlightening music) - [Announcer] Stanford University. - [Lecturer] All righty then, Lecture 13 of Stanford CS193p Spring of 2020. Today, our topic is persistence. That is to say, storing stuff that lives between launches of your application. Now, we've actually seen quite a bit of this stuff already. And we're gonna go into some more detail on th... Read More

Key Insights

• 👂 UserDefaults is a simple storage option for property lists and is often used for demos.
• 💨 Codable and JSON provide a way to convert custom structs into an interoperable format for storing or sending data.
• 📜 UIDocument is used for managing documents in apps that require document creation, although it is not recommended for final projects due to its advanced API and UIKit integration.
• 😀 Core Data is a powerful database system with SwiftUI integration and is the go-to option for storing significant amounts of data in iOS apps.
• 👻 CloudKit allows for storing data on the network in iCloud, providing the ability to share and sync data across devices.
• 📁 Storing data in the file system allows for more control and flexibility, with the data being accessible even if the app is deleted. The FileManager struct is used for file system operations.

Questions & Answers

Q: What are the advantages of using UserDefaults for storing data in iOS apps?

UserDefaults is simple and easy to use, making it great for demos and storing small amounts of data. It allows you to store property lists and works well for quickly getting started with data persistence in your app.

Q: How does CloudKit differ from Core Data for storing data in iOS apps?

CloudKit allows for storing data on the network in iCloud, making it accessible on all of the user's devices. It also provides features similar to UserDefaults and Core Data, such as storing key-value pairs and integrating with Core Data. Core Data, on the other hand, is a more powerful object-oriented database system with SwiftUI integration for managing larger amounts of data in your app.

Q: What is the benefit of using the file system for data storage in iOS apps?

Storing data in the file system allows for more control and flexibility compared to other storage options. It can be used to store documents and files in a structured way, making it easier to manage and access the data. Additionally, data stored in the file system can be backed up to iCloud and persists even if the app is deleted.

Q: How can CloudKit be used to share data between devices?

CloudKit allows you to store data on the network in iCloud, making it accessible on all of the user's devices. By using CloudKit, data can be synced and shared across devices, ensuring that the user can access the same data regardless of which device they are using.

Summary & Key Takeaways

• Persistence is the act of storing and managing data that lives between app launches.

• UserDefaults is a simple and limited storage option for property lists in iOS apps, often used for demos.

• Codable and JSON provide a way to convert custom structs into an interoperable format for storing or sending data.

• UIDocument is part of UIKit and is used for managing documents in apps that require document creation.

• Core Data is a powerful object-oriented database system with deep SwiftUI integration for managing significant amounts of data in iOS apps.

• CloudKit allows for storing and accessing data on the network in iCloud and has features similar to UserDefaults and Core Data.

• The file system in iOS devices can be accessed using URLs, Data, and the FileManager struct for managing files and directories.