how to pre-fill email field in GTMOAuth2ViewControllerTouch view

Question

how to pre-fill email field in GTMOAuth2ViewControllerTouch view ?

Is it possible ? Has any one tried this ?

I am using the standard way to create the view controller class and showing the gtm view modally

self.gtmVC = [[GTMOAuth2ViewControllerTouch alloc] initWithAuthentication:googleAuth authorizationURL:[GTMOAuth2SignIn googleAuthorizationURL] keychainItemName:kKeychainItemName delegate:self finishedSelector:@selector(viewController:finishedWithAuth:error:)];

Answer 1

There's no supported way of doing this. However, using Javascript, you can get it done. Here's some steps / code:

Wait for the Webview Loading to Complete

GTMOAuth2ViewControllerTouch defines a NSNotification that you can observe through the NSNotificationCenter. It's kGTMOAuth2WebViewStoppedLoading:

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(authControllerWebViewStoppedLoading:)
 name:kGTMOAuth2WebViewStoppedLoading
 object:nil];

The NSNotification object's userInfo dictionary will have a reference to the webview in it. GTMOAuth2ViewControllerTouch also allows public access to the webview. I used the latter in my app.

Use Javascript to Change the Email Input Entity

First, you should know that you can get the HTML of the page the webview is showing like so:

NSString *html = [self.authController.webView
                  stringByEvaluatingJavaScriptFromString:
                  @"document.body.innerHTML"];

You don't need it for this solution, but it will allow you to confirm that the HTML for the Email input entity still looks like the following:

<input id="Email" name="Email" type="email" 
      placeholder="Email" value="" spellcheck="false" class="">

Once you know that email input entity, you can then use javascript to change its text value:

- (void)authControllerWebViewStoppedLoading:(NSNotification *)notification
{
    // Assume emailAddress is a property that holds the email address you
    // you want to pre-populate the Email entity with....

    NSString *javascript = [NSString stringWithFormat:
                            @"var elem = document.getElementById(\"Email\");"
                            @"elem.value = \"%@\";", self.emailAddress];
    [self.authController.webView
     stringByEvaluatingJavaScriptFromString:javascript];
}

That's It

Obviously this solution runs the risk of having Google change things on their end without checking with you first. But, the worst that happens in that case is that the email stops pre-populating and your user has to type it in manually, at least until you can release an update.

Hope this helps.

Answer 2

I believe there is an easier way than using Javascript. Once you've created your controller, get GTMOAuth2SignIn and add additionalAuthorizationParameters with the user email address.

  #import "GTMOAuth2SignIn.h"

  GTMOAuth2ViewControllerTouch *authViewController = 
  [[GTMOAuth2ViewControllerTouch alloc] initWithScope:kGTLAuthScopeDriveFile
                                             clientID:kClientId
                                         clientSecret:kClientSecret
                                     keychainItemName:kKeychainItemName
                                             delegate:self
                                     finishedSelector:finishedSelector];

  GTMOAuth2SignIn *signIn = authViewController.signIn;
  signIn.additionalAuthorizationParameters = @{@"login_hint" : @"example@gmail.com"};

This is from the parameters list for OAuth2 for Installed Applications: https://developers.google.com/accounts/docs/OAuth2InstalledApp#formingtheurl

This worked for me at least.