gistfile1.m

// SERVER_NAME is a defined constant

// Create dictionary of search parameters
NSDictionary* dict = [NSDictionary dictionaryWithObjectsAndKeys:(__bridge id)(kSecClassInternetPassword),  kSecClass, SERVER_NAME, kSecAttrServer, kCFBooleanTrue, kSecReturnAttributes, nil];
    
// Remove any old values from the keychain
OSStatus err = SecItemDelete((__bridge CFDictionaryRef) dict);
    
// Create dictionary of parameters to add
NSData* passwordData = [credentials.password dataUsingEncoding:NSUTF8StringEncoding];
dict = [NSDictionary dictionaryWithObjectsAndKeys:(__bridge id)(kSecClassInternetPassword), kSecClass, SERVER_NAME, kSecAttrServer, passwordData, kSecValueData, credentials.username, kSecAttrAccount, nil];
    
// Try to save to keychain
err = SecItemAdd((__bridge CFDictionaryRef) dict, NULL);