Question

当我尝试获取keyChain值时，它返回一个包含以下内容的字符串：

Optional("[thing in the KeyChain]")

所以，我试图删除＆＃34; Optional＆＃34;通过使用循环：

var str = KeychainService.loadToken()

for(var i = 0; i < 9 ; i++)
{
    str[i] = ""
}

但是我收到了一个错误：NSString没有名为＆＃39; subscript＆＃39;

的成员

KeychainService类：

import Foundation
import Security

let serviceIdentifier = "MySerivice"
let userAccount = "authenticatedUser"
let accessGroup = "MySerivice"

// Arguments for the keychain queries
let kSecClassValue = kSecClass.takeRetainedValue() as NSString
let kSecAttrAccountValue = kSecAttrAccount.takeRetainedValue() as NSString
let kSecValueDataValue = kSecValueData.takeRetainedValue() as NSString
let kSecClassGenericPasswordValue = kSecClassGenericPassword.takeRetainedValue() as NSString
let kSecAttrServiceValue = kSecAttrService.takeRetainedValue() as NSString
let kSecMatchLimitValue = kSecMatchLimit.takeRetainedValue() as NSString
let kSecReturnDataValue = kSecReturnData.takeRetainedValue() as NSString
let kSecMatchLimitOneValue = kSecMatchLimitOne.takeRetainedValue() as NSString

class KeychainService: NSObject {

/**
* Exposed methods to perform queries.
* Note: feel free to play around with the arguments
* for these if you want to be able to customise the
* service identifier, user accounts, access groups, etc.
*/
internal class func saveToken(token: NSString) {
    self.save(serviceIdentifier, data: token)
}

internal class func loadToken() -> NSString? {
    var token = self.load(serviceIdentifier)

    return token
}

/**
* Internal methods for querying the keychain.
*/
private class func save(service: NSString, data: NSString) {
    var dataFromString: NSData = data.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)

    // Instantiate a new default keychain query
    var keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, userAccount, dataFromString], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecValueDataValue])

    // Delete any existing items
    SecItemDelete(keychainQuery as CFDictionaryRef)

    // Add the new keychain item
    var status: OSStatus = SecItemAdd(keychainQuery as CFDictionaryRef, nil)
}

private class func load(service: NSString) -> String? {
    // Instantiate a new default keychain query
    // Tell the query to return a result
    // Limit our results to one item
    var keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, userAccount, kCFBooleanTrue, kSecMatchLimitOneValue], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecReturnDataValue, kSecMatchLimitValue])

    var dataTypeRef :Unmanaged<AnyObject>?

    // Search for the keychain items
    let status: OSStatus = SecItemCopyMatching(keychainQuery, &dataTypeRef)

    let opaque = dataTypeRef?.toOpaque()

    var contentsOfKeychain: String?

    if let op = opaque? {
        let retrievedData = Unmanaged<NSData>.fromOpaque(op).takeUnretainedValue()

        // Convert the data retrieved from the keychain into a string
        contentsOfKeychain = NSString(data: retrievedData, encoding: NSUTF8StringEncoding)
    } else {
        println("Nothing was retrieved from the keychain. Status code \(status)")
    }

    return contentsOfKeychain
    }
}

我只是想删除str周围的可选项或者有更好的方法吗？

我从以下代码中获取此代码：

http://matthewpalmer.net/blog/2014/06/21/example-ios-keychain-swift-save-query/

Answer 1

您获得Optional("")，因为未解包可选值。您需要在对象后放置一个!，然后您再也无法获得Optional("")位。我会告诉你代码，但你还没有向我们展示print()声明。我在下面做了一些样本，我认为会复制这个问题，虽然我还没有尝试过。

var value:String?
value = "Hello, World"

print("The Value Is \(value)") // Prints "The Value Is Optional(Hello, World)"
print("The Value Is \(value!)")// Prints "The Value Is Hello, World"

我希望这能回答你的问题，或者至少指出你正确的方向，只要问你是否需要更多的信息或更好的例子。

Answer 2

这是一个Swift 2示例实现：

import Security

class ZLKeychainService: NSObject {

    var service = "Service"
    var keychainQuery :[NSString: AnyObject]! = nil

    func save(name name: NSString, value: NSString) -> OSStatus? {
        let statusAdd :OSStatus?

        guard let dataFromString: NSData = value.dataUsingEncoding(NSUTF8StringEncoding) else {
            return nil
        }

        keychainQuery = [
            kSecClass       : kSecClassGenericPassword,
            kSecAttrService : service,
            kSecAttrAccount : name,
            kSecValueData   : dataFromString]
        if keychainQuery == nil {
            return nil
        }

        SecItemDelete(keychainQuery as CFDictionaryRef)

        statusAdd = SecItemAdd(keychainQuery! as CFDictionaryRef, nil)

        return statusAdd;
    }

    func load(name name: NSString) -> String? {
        var contentsOfKeychain :String?

        keychainQuery = [
            kSecClass       : kSecClassGenericPassword,
            kSecAttrService : service,
            kSecAttrAccount : name,
            kSecReturnData  : kCFBooleanTrue,
            kSecMatchLimit  : kSecMatchLimitOne]
        if keychainQuery == nil {
            return nil
        }

        var dataTypeRef: AnyObject?
        let status: OSStatus = SecItemCopyMatching(keychainQuery, &dataTypeRef)

        if (status == errSecSuccess) {
            let retrievedData: NSData? = dataTypeRef as? NSData
            if let result = NSString(data: retrievedData!, encoding: NSUTF8StringEncoding) {
                contentsOfKeychain = result as String
            }
        }
        else {
            print("Nothing was retrieved from the keychain. Status code \(status)")
        }

        return contentsOfKeychain
    }
}

//Test:
let userName = "TestUser"
let userValue: NSString = "TestValue"
print("userName: '\(userName)'")
print("userValue: '\(userValue)'")

let kcs = ZLKeychainService()

kcs.save(name:userName, value: userValue)
print("Keychain Query \(kcs.keychainQuery)")

if let recoveredToken = kcs.load(name:userName) {
    print("Recovered Value: '\(recoveredToken)'")
}

输出：

userName：＆＃39; TestUser＆＃39;
  userValue：＆＃39; TestValue＆＃39;
  Keychain Query [acct：TestUser，v_Data：＆lt; 54657374 56616c75 65＆gt;，svce：Service，class：genp]
  恢复价值：＆＃39; TestValue＆＃39;

Answer 3

您可以在Keychain C API上使用Swift包装器，并完全避免上述问题。 https://github.com/deniskr/KeychainSwiftAPI

Answer 4

您将获得Optional（“”），因为未解开可选值，并且如果您想解开可选值以获取字符串值，请执行

yourValue.unsafelyUnwrapped

Answer 5

你实际上甚至不需要做任何事情。＆＃34;可选＆＃34;字符串不在实际数据中。这只是Swift似乎放在控制台输出上的东西，当它是一个未被打开的可选值时。 IE数据本身不包含字符串Optional。

如果你知道它包含数据，那么打开它还是很好的。

在尝试从KeyChain获取值时获取可选（“”）

5 个答案: