iphone使用keychain来存取 uuid

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 <Foundation/Foundation.h>  
#import <Security/Security.h>  
  
  
@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。

另外附上一篇写得更详细的e文：http://useyourloaf.com/blog/2010/3/29/simple-iphone-keychain-access.html