Lecture 8: Gestures JSON

TL;DR

Learn how to use UserDefaults to store data persistently and how to handle gestures in SwiftUI.

Transcript

• Stanford University. - Okay, welcome to lecture eight, Stanford CS193p, spring of 2020. I'm gonna try to keep the slides short today so we can jump into another big demo, but I need to talk about conceptual stuff behind a couple of things we're gonna do in the demo, namely UserDefaults, which is a very lightweight, persistent store that we're jus... Read More

Key Insights

• 🏪 UserDefaults is a simple way to store small user preferences persistently, but it is not suitable for storing large amounts of data or documents.
• 👂 Property lists are a common format for data storage in UserDefaults, and Codable can be used to convert custom structs into property list format.

Questions & Answers

Q: What are some ways to store data persistently in iOS?

Data can be stored in the file system, SQL databases, iCloud, or by using third-party options such as network databases.

Q: What are the limitations of UserDefaults?

UserDefaults is limited in the types of data it can store; it can only store basic types like strings, integers, booleans, dates, and arrays.

Q: How can Codable be used with UserDefaults?

Codable can be used to convert a struct into a data object that can be stored in UserDefaults. By implementing the Encodable and Decodable protocols, the struct can be easily encoded into a property list format that is compatible with UserDefaults.

Q: How can gestures be handled in SwiftUI?

Gestures can be handled in SwiftUI by using the .gesture modifier and specifying the gesture to recognize. The .onEnded function can be used to handle the gesture when it ends, and .updating can be used to handle the gesture as it is occurring.

Summary & Key Takeaways

• UserDefaults is a lightweight, persistent store in iOS that can be used to store data persistently, although it is best suited for small user preferences.

• To store data in UserDefaults, use the set(forKey:) function, specifying the object and key. To retrieve data, use functions like integer(forKey:), data(forKey:), and stringArray(forKey:).

• Gestures in SwiftUI allow you to get input from the user using their fingers. Use the .gesture modifier to make a view recognize a gesture, and use functions like .onEnded to handle the gesture.