iOS 钥匙串服务：kSecAttrGeneric Key 仅允许特定值

iOS钥匙串服务是一种安全存储和管理敏感信息的方式，可以用于存储密码、证书、令牌等重要数据。在iOS钥匙串服务中，kSecAttrGeneric Key是一种用于标识和访问存储在钥匙串中的数据的键。与其他属性键相比，kSecAttrGeneric Key具有一些特殊的限制和要求。

swift
import UIKit
import Security
// 定义kSecAttrGeneric Key
let genericKey = "com.example.app.genericKey"
// 存储数据项
func saveDataToKeychain(data: String) {
    if let dataFromString = data.data(using: .utf8) {
        let keychainQuery: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrGeneric as String: genericKey,
            kSecValueData as String: dataFromString
        ]
        
        let status = SecItemAdd(keychainQuery as CFDictionary, nil)
        if status == errSecSuccess {
            print("Data saved to keychain")
        } else {
            print("Failed to save data to keychain")
        }
    }
}
// 从钥匙串中读取数据项
func readDataFromKeychain() -> String? {
    let keychainQuery: [String: Any] = [
        kSecClass as String: kSecClassGenericPassword,
        kSecAttrGeneric as String: genericKey,
        kSecMatchLimit as String: kSecMatchLimitOne,
        kSecReturnAttributes as String: true,
        kSecReturnData as String: true
    ]
    
    var item: CFTypeRef?
    let status = SecItemCopyMatching(keychainQuery as CFDictionary, &item)
    
    if status == errSecSuccess {
        if let existingItem = item as? [String: Any],
           let data = existingItem[kSecValueData as String] as? Data,
           let dataString = String(data: data, encoding: .utf8) {
            return dataString
        }
    }
    
    return nil
}
// 测试代码
let dataToSave = "Hello, Keychain!"
saveDataToKeychain(data: dataToSave)
if let retrievedData = readDataFromKeychain() {
    print("Retrieved data from keychain: \(retrievedData)")
} else {
    print("Failed to retrieve data from keychain")
}