如何在Xcode 9.2中的应用程序构建中保存登录凭据

#import <Security/Security.h>

- (void)saveCredentialsToKeychainWithUsername:(NSString *)username password:(NSString *)password {
    NSDictionary *attributes = @{
        (__bridge id)kSecClass: (__bridge id)kSecClassInternetPassword,
        (__bridge id)kSecAttrServer: @"your.server.com",
        (__bridge id)kSecAttrAccount: username,
        (__bridge id)kSecValueData: [password dataUsingEncoding:NSUTF8StringEncoding]
    };
    
    OSStatus status = SecItemAdd((__bridge CFDictionaryRef)attributes, NULL);
    if (status != errSecSuccess) {
        NSLog(@"Failed to save credentials to Keychain. Error: %d", (int)status);
    }
}

- (NSString *)retrievePasswordFromKeychainWithUsername:(NSString *)username {
    NSDictionary *query = @{
        (__bridge id)kSecClass: (__bridge id)kSecClassInternetPassword,
        (__bridge id)kSecAttrServer: @"your.server.com",
        (__bridge id)kSecAttrAccount: username,
        (__bridge id)kSecReturnData: @YES
    };
    
    CFTypeRef result = NULL;
    OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)query, &result);
    if (status == errSecSuccess && result != NULL) {
        NSData *passwordData = (__bridge_transfer NSData *)result;
        NSString *password = [[NSString alloc] initWithData:passwordData encoding:NSUTF8StringEncoding];
        return password;
    } else {
        NSLog(@"Failed to retrieve password from Keychain. Error: %d", (int)status);
        return nil;
    }
}