What are various ways to persist data in iOS?

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There are several ways to persist data in iOS, each with its own benefits and trade-offs. Some of the most common ways to persist data in iOS are:

• UserDefaults: UserDefaults is a simple key-value store that allows you to save small amounts of data, such as user preferences or settings. To save a value in UserDefaults, you can use the set method, like this:

let userDefaults = UserDefaults.standard
userDefaults.set("value", forKey: "key")

To retrieve a value from UserDefaults, you can use the value(forKey:) method, like this:

let userDefaults = UserDefaults.standard
if let value = userDefaults.value(forKey: "key") as? String {
  print(value) // Prints "value"
}

• Keychain: The Keychain is a secure store for sensitive data, such as passwords or cryptographic keys. To save a value in the Keychain, you can use the SecItemAdd function from the Security framework, like this:

let query: [String: Any] = [
  kSecClass as String: kSecClassGenericPassword,
  kSecAttrAccount as String: "key",
  kSecValueData as String: "value".data(using: .utf8)!
]

let status = SecItemAdd(query as CFDictionary, nil)

To retrieve a value from the Keychain, you can use the SecItemCopyMatching function, like this: