Lecture 11: Error Handling Persistence

TL;DR

This article discusses the concept of persistence in iOS app development and explores how to handle errors in Swift programming.

Transcript

(gentle music) - [Announcer] Stanford University. - [Instructor] Hello everybody, it's Lecture 11 of Stanford CS193p in Spring of 2021. Our primary topic today is persistence, storing things in a filesystem and other places. But before we talk about that we need to cover another little topic here which comes up quite a bit when we're talking about ... Read More

Key Insights

• 🏪 Persistence involves storing data permanently in various locations, such as the filesystem, databases, or iCloud.
• 🍗 Error handling in Swift involves using the throws and try keywords to handle errors thrown by functions.
• 👨‍🦱 The FileManager class and URLs are used to access and manipulate the filesystem in Swift.
• 👻 Codable is a powerful protocol in Swift that allows for easy conversion between objects and JSON data for storage.

Questions & Answers

Q: What does it mean for a function to throw an error in Swift?

When a function is marked with the throws keyword, it means that it can throw an error during its execution. This is usually used for fatal errors or unexpected situations.

Q: How can you handle errors thrown by a function in Swift?

Errors thrown by a function can be handled using the do-catch statement. Inside the do block, you call the function that can throw an error, and inside the catch block, you handle the error.

Q: What is the purpose of UserDefaults in iOS app development?

UserDefaults is used for lightweight data storage in iOS apps, such as user preferences. It allows you to store and retrieve simple data types like strings, ints, and booleans.

Q: How can you make a custom struct or enum Codable in Swift?

To make a custom struct or enum Codable, you need to make it conform to the Codable protocol. This involves implementing the encode(to encoder:) function for encoding and the init(from decoder:) function for decoding.

Summary & Key Takeaways

• Persistence is the process of storing data permanently in various locations, such as the filesystem, iCloud, or a database.

• Error handling in Swift involves using the throws keyword and the try keyword to handle errors that can occur during function calls.

• The FileManager class in Swift is used to access the filesystem, and URLs are used to specify file locations.

• Codable is a protocol in SwiftUI that allows for the easy conversion of structs and enums into JSON data for storage.

• UserDefaults is an old API in Swift that is used for lightweight data storage, such as user preferences.