Send email in Gmail API - Objective C

问题

We are working on an iOS project that involves sending emails through the Gmail API and we are having trouble finding documentation on how to actually do this.

First, we haven't completely figured out authentication. We are using AppAuth to handle that, and it's worked pretty well so far, but we are not quite sure how to link that up to the Gmail API in our code.

Second, how do we send the message itself? We have the content and everything formatted, we just can't figure out how to actually send the message. All we are looking to do is send a simple message to a specified email address from the user's own email account; no attachments or anything like that. We have seen a couple swift examples, however we would prefer to use Objective C. Any ideas on how we could do this?

Update:

After playing around with things a bit more, we found another way to connect to Gmail. Instead of using the classes from the Google API Objective C Client for REST, we are simply trying to send the email using an HTTP POST method. This appears to be way easier than dealing with all of the errors we were getting before. The only problem we have now is that we still can't quite send messages. With nearly everything we've tried, the API just creates an empty message and puts it in our Sent mailbox; that's it. Here's what we have right now:

- (void)sendEmail{
    NSURL *userinfoEndpoint = [NSURL URLWithString:@"https://www.googleapis.com/upload/gmail/v1/users/TEST_USERNAME/messages/send?uploadType=media"];
    NSString *currentAccessToken = _authState.lastTokenResponse.accessToken;

    [self logMessage:@"Trying to authenticate...."];

    // Handle refreshing tokens

    NSString *message = [NSString stringWithFormat:@"{\"raw\": \"%@\"}",[self generateMessage]];
    NSLog(@"%@", message);

    // creates request to the userinfo endpoint, with access token in the Authorization header
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:userinfoEndpoint];
    NSString *authorizationHeaderValue = [NSString stringWithFormat:@"Bearer %@", accessToken];
    [request addValue:authorizationHeaderValue forHTTPHeaderField:@"Authorization"];
    [request setHTTPMethod:@"POST"];
    [request setValue:@"message/rfc822" forHTTPHeaderField:@"Content-Type"];
    [request setValue:[NSString stringWithFormat:@"%lu", (unsigned long)[message length]] forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody:[message dataUsingEncoding:NSUTF8StringEncoding];

    NSURLSessionConfiguration *configuration =
    [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
                                                          delegate:nil
                                                     delegateQueue:nil];
    // performs HTTP request
    NSURLSessionDataTask *postDataTask =
    [session dataTaskWithRequest:request
               completionHandler:^(NSData *_Nullable data,
                                   NSURLResponse *_Nullable response,
                                   NSError *_Nullable error) {
                  // Handle response
               }];

    [postDataTask resume];
}];

}
- (NSString *)generateMessage{
    NSString *message = [NSString stringWithFormat:@"From: <TEST_USER@domain.com>\nTo: <TEST_USER@domain.com>\nSubject: Test\n\nThis is a test"];
    NSString *rawMessage = [message stringByReplacingOccurrencesOfString:@"\\n" withString:@"\n"];

    NSData *encodedMessage = [rawMessage dataUsingEncoding:NSUTF8StringEncoding];
    NSString *encoded = [encodedMessage base64EncodedStringWithOptions:0];
    NSLog(@"%@", encoded);

    return encoded;
}

We have tested the encoding part and it is making a proper base64 string, however after that point, something clearly is not formatted right or something. We get a confirmation that the message was successfully created, however all the API does is create an empty email with no recipient, subject, or body. Any ideas on what we could do to get this to work?

回答1:

I'm not an expert in this but I remembered we have done something similar in the past. Follow the instructions at the following link and make sure that you select the proper option in Gmail API wizard

https://developers.google.com/gmail/api/quickstart/ios?ver=objc

I hope you find this helpful

回答2:

After numerous experimentations, here is the code that seems to finally work for me, i worked it off your example above.

1st you need to create google project in dev console, get its Client ID and Api-Key(this may not be necessary) and implement Google SignIn in AppDelegete in - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions method:

[GIDSignIn sharedInstance].clientID = @"your proj client id here";
[GIDSignIn sharedInstance].delegate = self;
[GIDSignIn sharedInstance].scopes=[NSArray arrayWithObjects:@"https://www.googleapis.com/auth/gmail.send",@"https://www.googleapis.com/auth/gmail.readonly",@"https://www.googleapis.com/auth/gmail.modify", nil];

Now sending emails:

// refresh token
appDelegate.delAuthAccessToken=@"";
[[GIDSignIn sharedInstance] signInSilently];
NSDate *timeStart = [NSDate date];
NSTimeInterval timeSinceStart=0;
while([appDelegate.delAuthAccessToken isEqualToString:@""] && timeSinceStart<10){//wait for new token but no longer than 10s should be enough
    [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                             beforeDate:[NSDate dateWithTimeIntervalSinceNow:1.0f]];//1sec increment actually ~0.02s
    timeSinceStart = [[NSDate date] timeIntervalSinceDate:timeStart];
}
if (timeSinceStart>=10) {//timed out
    return;
}

//compose rfc2822 message AND DO NOT base64 ENCODE IT and DO NOT ADD {raw etc} TOO, put 'To:' 1st, add \r\n between the lines and double that before the actual text message
NSString *message = [NSString stringWithFormat:@"To: %@\r\nFrom: %@\r\nSubject: EzPic2Txt\r\n\r\n%@", appDelegate.delToEmails, appDelegate.delAuthUserEmail, appDelegate.delMessage];

NSURL *userinfoEndpoint = [NSURL URLWithString:@"https://www.googleapis.com/upload/gmail/v1/users/me/messages/send?uploadType=media"];

NSLog(@"%@", message);

//create request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:userinfoEndpoint];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:[message dataUsingEncoding:NSUTF8StringEncoding]];//message is plain UTF8 string

//add all headers into session config, maybe ok adding to request too
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
configuration.requestCachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
configuration.HTTPAdditionalHeaders = @{
 @"api-key"       : @"api-key here, may not need it though",
 @"Authorization" : [NSString stringWithFormat:@"Bearer %@", appDelegate.delAuthAccessToken],
 @"Content-type"  : @"message/rfc822",
 @"Accept"        : @"application/json",
 @"Content-Length": [NSString stringWithFormat:@"%lu", (unsigned long)[message length]]
 };
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration];

 // performs HTTP request
NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request
                                                completionHandler:^(NSData *_Nullable data, NSURLResponse *_Nullable response, NSError *_Nullable error) {
                                                    // Handle response
                                                }];
 [postDataTask resume];

Hope it helps somebody

In my app I used to be able to use MailCore2 but it got blocked by Google since it works only with full permissions. I was allowed by Google to use only send, readonly and modify scopes. There is no guide lines how to use their "great restful api" with Gmail in iOS though, so it seems like HTTP POST is the last resort until they shut it down too.

来源：https://stackoverflow.com/questions/42777107/send-email-in-gmail-api-objective-c

标签

ios

objective-c

google-api

gmail-api

appauth