UserDefaults for simple values in iOS Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is UserDefaults used for in iOS development?

UserDefaults is used to store small pieces of data like settings or preferences that need to persist between app launches.

beginner

How do you save a simple string value "Hello" for the key "greeting" using UserDefaults in Swift?

Use UserDefaults.standard.set("Hello", forKey: "greeting") to save the string.

beginner

How do you retrieve a string value for the key "greeting" from UserDefaults safely?

Use UserDefaults.standard.string(forKey: "greeting"). It returns an optional string, so you can safely unwrap it.

intermediate

Can UserDefaults store complex objects like custom classes directly?

No, UserDefaults is meant for simple data types like strings, numbers, booleans, and arrays. For complex objects, you need to encode them first.

beginner

What happens if you try to read a value from UserDefaults for a key that does not exist?

You get nil or a default value depending on the method used. For example, string(forKey:) returns nil if the key is missing.

Which method saves a boolean value to UserDefaults?

A UserDefaults.standard.set(true, forKey: "isOn")

B UserDefaults.standard.bool(forKey: "isOn")

C UserDefaults.standard.getBool("isOn")

D UserDefaults.standard.saveBool(true, "isOn")

The set(_:forKey:) method saves values. The bool(forKey:) method reads a boolean.

What type of data can UserDefaults store directly?

A Images and videos

B Strings, numbers, booleans, arrays, dictionaries

C Only strings

D Custom classes without encoding

UserDefaults supports simple data types like strings, numbers, booleans, arrays, and dictionaries.

How do you remove a value for a key from UserDefaults?

A UserDefaults.standard.clearKey("key")

B UserDefaults.standard.delete("key")

C UserDefaults.standard.removeObject(forKey: "key")

D UserDefaults.standard.set(nil, forKey: "key")

removeObject(forKey:) deletes the value for the given key.

What does UserDefaults.standard.string(forKey: "name") return if "name" does not exist?

A "" (empty string)

B 0

C Throws an error

D nil

It returns nil if the key does not exist.

Why should UserDefaults not be used for storing large data?

A It is designed for small, simple data and large data can slow down the app.

B It cannot store any data larger than 1 KB.

C It deletes large data automatically.

D It encrypts large data which is slow.

UserDefaults is optimized for small pieces of data like settings, not large files.

Explain how to save and retrieve a user's preferred theme (dark or light) using UserDefaults in Swift.

Think about storing true or false for dark mode preference.

Describe the types of data suitable for UserDefaults and why it is not recommended for storing large files.

Consider what UserDefaults is designed for and what it is not.