Keychain 中存储的字符串有长度限制吗

Keychain是iOS平台上的一种安全存储机制，用于保存应用程序的敏感信息，如用户密码、令牌等。在使用Keychain存储字符串时，是存在长度限制的。

swift
import UIKit
import Security
func saveStringToKeychain(string: String, forKey key: String) -> Bool {
    if let data = string.data(using: .utf8) {
        let query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrAccount as String: key,
            kSecValueData as String: data,
            kSecAttrAccessible as String: kSecAttrAccessibleWhenUnlocked
        ]
        
        SecItemDelete(query as CFDictionary)
        let status = SecItemAdd(query as CFDictionary, nil)
        return status == errSecSuccess
    }
    
    return false
}
func getStringFromKeychain(forKey key: String) -> String? {
    let query: [String: Any] = [
        kSecClass as String: kSecClassGenericPassword,
        kSecAttrAccount as String: key,
        kSecReturnData as String: true,
        kSecMatchLimit as String: kSecMatchLimitOne
    ]
    
    var result: AnyObject?
    let status = SecItemCopyMatching(query as CFDictionary, &result)
    
    if status == errSecSuccess, let data = result as? Data {
        return String(data: data, encoding: .utf8)
    }
    
    return nil
}
// 存储字符串到Keychain
let stringToSave = "This is a test string to save in Keychain."
let saveResult = saveStringToKeychain(string: stringToSave, forKey: "TestKey")
if saveResult {
    print("String saved to Keychain successfully.")
} else {
    print("Failed to save string to Keychain.")
}
// 从Keychain获取字符串
if let retrievedString = getStringFromKeychain(forKey: "TestKey") {
    print("Retrieved string from Keychain: \(retrievedString)")
} else {
    print("Failed to retrieve string from Keychain.")
}