iOS的keychain服务提供了一种安全的保存私密信息（密码，序列号，证书等）的方式。每个ios程序都有一个独立的keychain存储。从ios 3.0开始，跨程序分享keychain变得可行。
下面就使用keychain来实现存取用户名和密码。
苹果已经有现成的类封装好了keychain,KeychainItemWrapper.h和KeychainItemWrapper.m文件,可以在GenericKeychain实例里找到。
但是这里我只需要存取用户名和密码，就不用苹果提供的类了，自己写个简单的类来实现就好。
代码如下：
CHKeychain.h
#import #import @interface CHKeychain : NSObject+ (void)save:(NSString *)service data:(id)data;+ (id)load:(NSString *)service;+ (void)delete:(NSString *)service;@end
CHKeychain.m
#import "CHKeychain.h"@implementation CHKeychain+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service { return [NSMutableDictionary dictionaryWithObjectsAndKeys: (id)kSecClassGenericPassword,(id)kSecClass, service, (id)kSecAttrService, service, (id)kSecAttrAccount, (id)kSecAttrAccessibleAfterFirstUnlock,(id)kSecAttrAccessible, nil];}+ (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);}+ (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:(NSData *)keyData]; } @catch (NSException *e) { NSLog(@"Unarchive of %@ failed: %@", service, e); } @finally {} } if (keyData) CFRelease(keyData); return ret;}+ (void)delete:(NSString *)service { NSMutableDictionary *keychainQuery = [self getKeychainQuery:service]; SecItemDelete((CFDictionaryRef)keychainQuery);}@end首先需要定义几个字符串用来做key：
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";
把用户名和密码存入keychain：
NSMutableDictionary *usernamepasswordKVPairs = [NSMutableDictionary dictionary];[usernamepasswordKVPairs setObject:txtfldUsername.text forKey:KEY_USERNAME];[usernamepasswordKVPairs setObject:txtfldPassword.text forKey:KEY_PASSWORD];[CHKeychain save:KEY_USERNAME_PASSWORD data:usernamepasswordKVPairs];
从keychain中取出用户名和密码：
NSMutableDictionary *usernamepasswordKVPairs = (NSMutableDictionary *)[CHKeychain load:KEY_USERNAME_PASSWORD];txtfldUsername.text = [usernamepasswordKVPairs objectForKey:KEY_USERNAME];txtfldPassword.text = [usernamepasswordKVPairs objectForKey:KEY_PASSWORD];
删除一个keychain item:
[CHKeychain delete:KEY_USERNAME_PASSWORD];
这样一个简单的使用keychain存取用户名密码的功能就做好了。
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