通常情况下，可以用NSUserDefaults存储数据信息，但是对于一些私密信息，比如账号、密码等等，就需要使用更为安全的keychain了。keyChain是苹果提供的一种安全的保存用户名、密码、证书的方式，将敏感信息保存在keychain中后，这些信息不会随着app的卸载而丢失，除非开发人员在app中手动删除敏感信息，否则，这些信息将会一直保存在keychain中。
** 在使用keychain时，我们首先要将security.framework引入到工程中**
自定义一个类，取名KeyChain，头文件.h如下：
#import <Foundation/Foundation.h>
#import <Security/Security.h>
@interface KeyChain : NSObject
// save username and password to keychain
+ (void)save:(NSString *)service data:(id)data;
// take out username and passwore from keychain
+ (id)load:(NSString *)service;
// delete username and password from keychain
+ (void)delete:(NSString *)service;
@end
在实现文件中.m中，我们这样写：
#import "KeyChain.h"
@implementation KeyChain
+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {
return [NSMutableDictionary dictionaryWithObjectsAndKeys:
(id)kSecClassGenericPassword,(id)kSecClass,
service, (id)kSecAttrService,
service, (id)kSecAttrAccount,
(id)kSecAttrAccessibleAfterFirstUnlock,(id)kSecAttrAccessible,
nil];
}
#pragma mark 写入
+ (void)save:(NSString *)service data:(id)data {
//Get search dictionary
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Delete old item before add new item
SecItemDelete((CFDictionaryRef)keychainQuery);
//Add new object to search dictionary(Attention:the data format)
[keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(id)kSecValueData];
//Add item to keychain with the search dictionary
SecItemAdd((CFDictionaryRef)keychainQuery, NULL);
}
#pragma mark 读取
+ (id)load:(NSString *)service {
id ret = nil;
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Configure the search setting
//Since in our simple case we are expecting only a single attribute to be returned (the password) we can set the attribute kSecReturnData to kCFBooleanTrue
[keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];
[keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
CFDataRef keyData = NULL;
if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {
@try {
ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge NSData *)keyData];
} @catch (NSException *e) {
NSLog(@"Unarchive of %@ failed: %@", service, e);
} @finally {
}
}
if (keyData)
CFRelease(keyData);
return ret;
}
#pragma mark 删除
+ (void)delete:(NSString *)service {
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
SecItemDelete((CFDictionaryRef)keychainQuery);
}
@end
下边是使用这个类,在viewController中，我们定义几个字符串类型的标识符
#import "ViewController.h"
#import "KeyChain.h"
@interface ViewController ()
@end
NSString * const KEY_USERNAME_PASSWORD = @"com.company.app.usernamepassword";
NSString * const KEY_USERNAME = @"com.company.app.username";
NSString * const KEY_PASSWORD = @"com.company.app.password";
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSMutableDictionary *userNamePasswordKVPairs = [NSMutableDictionary dictionary];
[userNamePasswordKVPairs setObject:@"userName" forKey:KEY_USERNAME];
[userNamePasswordKVPairs setObject:@"password" forKey:KEY_PASSWORD];
// Do any additional setup after loading the view, typically from a nib.
// A、将用户名和密码写入keychain
[KeyChain save:KEY_USERNAME_PASSWORD data:userNamePasswordKVPairs];
// B、从keychain中读取用户名和密码
NSMutableDictionary *readUsernamePassword = (NSMutableDictionary *)[KeyChain load:KEY_USERNAME_PASSWORD];
NSString *userName = [readUsernamePassword objectForKey:KEY_USERNAME];
NSString *password = [readUsernamePassword objectForKey:KEY_PASSWORD];
NSLog(@"username = %@", userName);
NSLog(@"password = %@", password);
// C、将用户名和密码从keychain中删除
[KeyChain delete:KEY_USERNAME_PASSWORD];
}
运行结果如下：
2016-08-15 16:36:08.588 KeyChain[8563:1595142] username = userName
2016-08-15 16:36:08.589 KeyChain[8563:1595142] password = password
