Question

我是iOS新手。我需要在本地保存数据。在android中我们可以在sharedPreferences中保存数据。并且开发人员可以清除整个共享首选项，也可以删除/删除特定键。

我正在使用钥匙串。但现在我想删除/删除一个键。但我对如何做到这一点有疑问。这是我从SO获得的钥匙串代码。

    public class KeychainService: NSObject {

    static let USER_PIN : String = "USER_PIN"
    static let LOGGEDIN_ID : String = "LOGGEDIN_ID"
    static let USER_NAME : String = "USER_NAME"
    static let IS_USER_LOGGEDIN : String = "IS_USER_LOGGEDIN"


    static let IS_APP_SETTINGS_DOWNLOADED : String = "IS_APP_SETTINGS_DOWNLOADED"
    static let APP_SETTINGS_DOWNLOADED : String = "APP_SETTINGS_DOWNLOADED"
    static let APP_NAME : String = "APP_NAME"

    class func iterateKeychainItems(log: Bool, delete: Bool) {
        let secItemClasses = [
            kSecClassGenericPassword,
            kSecClassInternetPassword,
            kSecClassCertificate,
            kSecClassKey,
            kSecClassIdentity
        ]

        if (log) {
            for secItemClass in secItemClasses {
                let query: [String: Any] = [
                    kSecReturnAttributes as String: kCFBooleanTrue,
                    kSecMatchLimit as String: kSecMatchLimitAll,
                    kSecClass as String: secItemClass
                ]

                var result: AnyObject?
                let status = SecItemCopyMatching(query as CFDictionary, &result)
                if status == noErr {
                    print(result as Any)
                }
            }
            print("AppUsageMetadata.iterateKeychainItems ended.")
        }

        if (delete) {
            for secItemClass in secItemClasses {
                let dictionary = [kSecClass as String:secItemClass]
                SecItemDelete(dictionary as CFDictionary)
            }
        }
    }

        class func save(key: String, data: Data) -> OSStatus {
            let query = [
                kSecClass as String       : kSecClassGenericPassword as String,
                kSecAttrAccount as String : key,
                kSecValueData as String   : data ] as [String : Any]

            SecItemDelete(query as CFDictionary)

            return SecItemAdd(query as CFDictionary, nil)
        }

        class func load(key: String) -> Data? {
            let query = [
                kSecClass as String       : kSecClassGenericPassword,
                kSecAttrAccount as String : key,
                kSecReturnData as String  : kCFBooleanTrue,
                kSecMatchLimit as String  : kSecMatchLimitOne ] as [String : Any]

            var dataTypeRef: AnyObject? = nil

            let status: OSStatus = SecItemCopyMatching(query as CFDictionary, &dataTypeRef)

            if status == noErr {
                return dataTypeRef as! Data?
            } else {
                return nil
            }
        }

        class func createUniqueID() -> String {
            let uuid: CFUUID = CFUUIDCreate(nil)
            let cfStr: CFString = CFUUIDCreateString(nil, uuid)

            let swiftString: String = cfStr as String
            return swiftString
        }
    }

    extension Data {

        init<T>(from value: T) {
            var value = value
            self.init(buffer: UnsafeBufferPointer(start: &value, count: 1))
        }

        func to<T>(type: T.Type) -> T {
            return self.withUnsafeBytes { $0.pointee }
        }




}

所以现在告诉我如何删除一个键/项目。例如，我想删除IS_USER_LOGGEDIN键。怎么做？请帮帮我

Answer 1

Theres是一个很好的包装器，用于访问GitHub上的系统密钥链：

SAMKeyChain

只需使用＆＃34; setPassword＆＃34;和＆＃34; deletePassword＆＃34;满足您的需求。

Answer 2

您可以像共享偏好设置一样使用 UserDefaults 对于 Swift 3： 对于使用键设置字符串值 UserDefaults.standard.set（“2”，forKey：“LOGINID”）

使用key获取字符串值 让LoginID = UserDefaults.standard.string（forKey：“LOGINID”）！

按键删除 UserDefaults.standard.removeObject（forKey：“LOGINID”）

适用于Swift2.2 let defaults = NSUserDefaults.standardUserDefaults（） defaults.setObject（“2”，forKey：“LOGINID”）

钥匙串如何仅删除特定项目

2 个答案: