前言

对于iOS的数据持久化，小的数据我们使用最多的肯定是UserDefaults，但是UserDefaults的弊端也比较明显：存取都是重写整个文件，效率低下、无法存储太大的数据、安全性低，很容易被攻破；当然这些只是题外话，我们今天要讲的KeyChain钥匙串，虽然也不能存储太大的数据，但是它的安全性很高，还可以随着iCould同步，苹果官方也推荐我们使用这个 来存储账号密码等重要的信息，那我们来看看怎么使用KeyChain。

keyChain

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@enum Class Value Constants
@discussion Predefined item class constants used to get or set values in a dictionary. The kSecClass constant is the key and its value is one of the constants defined here. Note: on Mac OS X 10.6, only items of class kSecClassInternetPassword are supported.
@constant kSecClassInternetPassword Specifies Internet password items.
@constant kSecClassGenericPassword Specifies generic password items.
@constant kSecClassCertificate Specifies certificate items.
@constant kSecClassKey Specifies key items.
@constant kSecClassIdentity Specifies identity items.

我们普通账号密码就使用kSecClassGenericPassword（一般密码）就好，keyChain的常用方法如下

public func SecItemCopyMatching(_ query: CFDictionary, _ result: UnsafeMutablePointer<CoreFoundation.CFTypeRef?>?) -> OSStatus
public func SecItemAdd(_ attributes: CFDictionary, _ result: UnsafeMutablePointer<CoreFoundation.CFTypeRef?>?) -> OSStatus
public func SecItemUpdate(_ query: CFDictionary, _ attributesToUpdate: CFDictionary) -> OSStatus
public func SecItemDelete(_ query: CFDictionary) -> OSStatus

顾名思义，分别是查找、添加、更新和删除，直接将我们设置好的Item的字段作为参数传入就可以调用，不过我们这里适当封装一下，便于我们使用

工具封装

代码如下

//
//  KeyChainTool.swift
//
//  Created by Fxxx on 2017/12/6.
//  Copyright © 2017年 Fxxx. All rights reserved.
//

import UIKit

class KeyChainTool: NSObject {
    
    //工具单例类
    static let shared = KeyChainTool()
    
    //item字典
    private func keyChainQueryDictionaryWithKey(key: String) -> NSMutableDictionary {
        
        let dic = NSMutableDictionary()
        dic.setObject(kSecClassGenericPassword, forKey: kSecClass as! NSCopying)
        dic.setObject(kSecAttrAccessibleAfterFirstUnlock, forKey: kSecAttrAccessible as! NSCopying)
        dic.setObject(key, forKey: kSecAttrService as! NSCopying)
        dic.setObject(key, forKey: kSecAttrAccount as! NSCopying)
        return dic
        
    }
    
    //新增
    func addToKeyChain(data: Any, key: String) -> Bool {
        
        let dic = self.keyChainQueryDictionaryWithKey(key: key)
        SecItemDelete(dic)
        dic.setObject(NSKeyedArchiver.archivedData(withRootObject: data), forKey: kSecValueData as! NSCopying)
        let status = SecItemAdd(dic, nil)
        if status == noErr {
            return true
        }
        return false
        
    }
    
    //更新
    func updateData(data: Any, key: String) -> Bool {
        
        let oldDic = self.keyChainQueryDictionaryWithKey(key: key)
        guard SecItemCopyMatching(oldDic, nil) == noErr else {
            return false
        }
        let updateDic = NSMutableDictionary()
        updateDic.setObject(NSKeyedArchiver.archivedData(withRootObject: data), forKey: kSecValueData as! NSCopying)
        let status = SecItemUpdate(oldDic, updateDic)
        if status == errSecSuccess {
            return true
        }
        return false
        
    }
    
    //获取
    func getDataForKey(key: String) -> Any? {
        
        var result: Any?
        let dic = self.keyChainQueryDictionaryWithKey(key: key)
        dic.setObject(kCFBooleanTrue, forKey: kSecReturnData as! NSCopying)
        dic.setObject(kSecMatchLimitOne, forKey: kSecMatchLimit as! NSCopying)
        var queryResult: CFTypeRef?
        if SecItemCopyMatching(dic, &queryResult) == noErr {
            
            if queryResult != nil {
                result = NSKeyedUnarchiver.unarchiveObject(with: queryResult! as! Data)
            }
            
        }
        return result
        
    }
    
    //删除
    func removeDataForKey(key: String) -> Bool {
        
        let dic = self.keyChainQueryDictionaryWithKey(key: key)
        let status = SecItemDelete(dic)
        if status == noErr {
            return true
        }
        return false
        
    }
    
}

这里我使用了单例模式来优化，将主要的功能进行了封装，具体的使用操作在结尾Demo里，欢迎下载查看

Group分享

image.png

PS：之前看到很多教程，使用Keychain即使不分享也要打开Keychain Sharing，这里我试过了，不打开也不影响本地的存储和使用的，我使用的是Xcode9和swift4.

Demo下载

KeyChainDemo