IOS KeyChain理解及代码事例

对KeyChain的理解，可参照http://my.oschina.net/w11h22j33/blog/206713

文中利用KeyChain保存用户名和密码，用户名放在属性中，密码放在密码项中；其中对KeyChain项的增删改查，我个人觉得是有问题的，为了方面自己代码上的使用，也帮助阅读该文的其他读者更好的理解，我修正了代码如下：

</pre><p></p><p><pre name="code" class="objc">//存储/增加
-(IBAction)saveClicked:(id)sender{

if(_nameTF.text.length > 0 && _psdTF.text.length > 0) {
NSMutableDictionary* dic = [NSMutableDictionary dictionary];

[dic setObject:(__bridge_transfer id)kSecClassGenericPassword forKey:(__bridge_transfer id)kSecClass];
[dic setObject:_nameTF.text forKey:(__bridge_transfer id)kSecAttrAccount];
[dic setObject:[_psdTF.text dataUsingEncoding:NSUTF8StringEncoding] forKey:(__bridge_transfer id)kSecValueData];

OSStatus s = SecItemAdd((__bridge_retained CFDictionaryRef)dic, NULL);
NSLog(@"%d",s);
}

}

//获取/查询
-(IBAction)showClicked:(id)sender
{
if(_nameTF.text.length > 0) {
NSDictionary* query = [NSDictionary dictionaryWithObjectsAndKeys:
(__bridge_transfer id)kSecClassGenericPassword, (__bridge_transfer id)kSecClass,
_nameTF.text, (__bridge_transfer id)kSecAttrAccount,
kCFBooleanTrue, kSecReturnAttributes,nil];

CFTypeRef result = nil;
OSStatus s = SecItemCopyMatching((__bridge_retained CFDictionaryRef)query, &result);

NSLog(@"%d",s);
NSLog(@"%@",result);

if(s == noErr) {//通过用户名判断item项是否存在
NSMutableDictionary* dic = [NSMutableDictionary dictionary];
[dic setObject:_nameTF.text forKey: (__bridge_transfer id)kSecAttrAccount];
[dic setObject:(__bridge_transfer id)kCFBooleanTrue forKey:(__bridge_transfer id)kSecReturnData];
[dic setObject:(__bridge_transfer id)kSecClassGenericPassword forKey:(__bridge_transfer id)kSecClass];

CFDataRef dataRef = NULL;
if(SecItemCopyMatching((__bridge_retained CFDictionaryRef)dic, (CFTypeRef*)&dataRef) == noErr) {

NSData *data = (__bridge_transfer id)dataRef;
NSLog(@"%ld", data.length);

NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
}
}
}else{

NSDictionary* query = [NSDictionary dictionaryWithObjectsAndKeys:
(__bridge_transfer id)kSecClassGenericPassword,(__bridge_transfer id)kSecClass,
(__bridge_transfer id)kSecMatchLimitAll, (__bridge_transfer id)kSecMatchLimit,
(__bridge_transfer id)kCFBooleanTrue,(__bridge_transfer id)kSecReturnAttributes,nil];

CFArrayRef result = NULL;
OSStatus s = SecItemCopyMatching((__bridge_retained CFDictionaryRef)query, (CFTypeRef*)&result);

NSArray *array = (__bridge_transfer NSArray*)result;//(可以遍历所有keychain项)

NSLog(@"%d",s);
NSLog(@"%@",result);
}

}

//删除
-(IBAction)delClicked:(id)sender{

if(_nameTF.text.length > 0){
NSDictionary* query = [NSDictionary dictionaryWithObjectsAndKeys:(__bridge_transfer id)kSecClassGenericPassword,kSecClass,
_nameTF.text,kSecAttrAccount,nil];
OSStatus status = SecItemDelete((__bridge_retained CFDictionaryRef)query);
NSLog(@"%d",status);
}

}

//改
-(IBAction)modifyClicked:(id)sender{

if(_nameTF.text.length > 0 && _psdTF.text.length > 0) {
NSDictionary* query = [NSDictionary dictionaryWithObjectsAndKeys:
(__bridge_transfer id)kSecClassGenericPassword, (__bridge_transfer id)kSecClass,
_nameTF.text, (__bridge_transfer id)kSecAttrAccount,
(__bridge_transfer id)kCFBooleanTrue, (__bridge_transfer id)kSecReturnAttributes,nil];

CFTypeRef result = nil;
if(SecItemCopyMatching((__bridge_retained CFDictionaryRef)query, &result) == noErr)//存在才修改
{
//设置需要更新的属性列表，一定要删除kSecClass，因为不能update不该字段，否则会报错
NSMutableDictionary* update = [[NSMutableDictionary alloc]init];
[update setObject:[_psdTF.text dataUsingEncoding:NSUTF8StringEncoding] forKey:(__bridge_transfer id)kSecValueData];
[update removeObjectForKey:(__bridge_transfer id)kSecClass];

//设置查找条件，即根据这个条件找到keychain项
NSMutableDictionary* updateItem = [[NSMutableDictionary alloc]init];
[updateItem setObject:[query objectForKey:(__bridge_transfer id)kSecClass] forKey:(__bridge_transfer id)kSecClass];
[updateItem setObject:_nameTF.text forKey:(__bridge_transfer id)kSecAttrAccount];

//参数一表示要查虚的，参数二表示更新后的值
OSStatus status = SecItemUpdate((__bridge_retained CFDictionaryRef)updateItem, (__bridge_retained CFDictionaryRef)update);
NSLog(@"%d",status);
}
}
}