Features
The UserDefaults class provides access to the user's defaults database.
It stores data persistently across the app launches as long as the app is installed.
Access to the data is private to the app unless shared through App Groups.
Access to this database is thread-safe.
It is a key-value store that works through a property list (plist) file.
Supported data types include String, Bool, Date, Array, Dictionary, Data and Numbers.
Custom objects can be stored by encoding them as data.
We can use this to store non-sensitive data such as user preferences.
Usage
Utilising the default shared instance of UserDefaults.
import Foundation
UserDefaults.standard.set("Shivam", forKey: "firstname")
UserDefaults.standard.value(forKey: "firstname")
UserDefaults.standard.removeObject(forKey: "firstname")
Creating a UserDefaults that can be shared with multiple apps and extensions.
import Foundation
let defaults = UserDefaults(suiteName: "group.com.organisation.appname")!
defaults.set("Shivam", forKey: "firstname")
defaults.value(forKey: "firstname")
defaults.removeObject(forKey: "firstname")
Storing custom objects in UserDefaults.
import Foundation
struct Student: Codable {
let firstname: String
let lastname: String
let grade: Int
let subjects: Array<String>
let teachers: [String: String]
let profileImage: Data
let dateModified: Date
}
let student = Student(firstname: "John",
lastname: "Doe",
grade: 2,
subjects: ["Hindi", "English", "Maths"],
teachers: ["Hindi": "Teacher A", "English": "Teacher b", "Maths": "Teacher X"],
profileImage: Data(),
dateModified: Date())
let encoder = JSONEncoder()
do {
let data = try encoder.encode(student)
UserDefaults.standard.setValue(data, forKey: "StudentData")
} catch {
throw error
}
let decoder = JSONDecoder()
if let data = UserDefaults.standard.value(forKey: "StudentData") as? Data {
do {
let object = try decoder.decode(Student.self, from: data)
print(object)
} catch {
throw error
}
} else {
print("No data in UserDefaults.")
}
Using UserDefaults as a Property Wrapper
Check out this gist to use UserDefaults with Property Wrapper. This is a more generalized way to use in Projects.
