Facebook Logout is not working in new SDK V.4.1.0 in ios?

Question

Friends I want to integrate Facebook in my App, so that I am download new Facebook SDK v.4.1.0, for Facebook login button use the class of FBSDKLoginButton as below code in Swift.

if (FBSDKAccessToken.currentAccessToken() != nil)
{
    // User is already logged in, do work such as go to next view controller.

    // Or Show Logout Button
    let loginView : FBSDKLoginButton = FBSDKLoginButton()
    self.view.addSubview(loginView)
    loginView.center = self.view.center
    loginView.readPermissions = ["public_profile", "email", "user_friends"]
    loginView.delegate = self
    self.returnUserData()
}
else
{
    let loginView : FBSDKLoginButton = FBSDKLoginButton()
    self.loginButtonDidLogOut(loginView)
    self.view.addSubview(loginView)
    loginView.center = self.view.center
    loginView.readPermissions = ["public_profile", "email", "user_friends"]
    loginView.delegate = self
 }
}

As above code there is display "Log in with Facebook" button.

After Successfully login thare is display logout button. when I click on logout button then its delegate is called - delegate class FBSDKLoginButtonDelegate

Delegate method of logout :

func loginButtonDidLogOut(loginButton: FBSDKLoginButton!) {
    println("User Logged Out")

    FBSDKAccessToken.setCurrentAccessToken(nil)
    FBSDKProfile.setCurrentProfile(nil)

    let manager = FBSDKLoginManager()
    manager.logOut()

}

in delegate I am clear token and also called function of logout inside class of FBSDKLoginManager. But each time get authorized screen of user. Not get Login screen so that another user can't login with facebook. each time I have to clear browser history.

without clear browser history, There is not display login page so that another user can't login.

Qusetion : Facebook BUG

Each time display screen after logout :

Answer 1

I am also stuck in the same place. However surfing i came to following conclusion.

First lets know the meaning of SingleSignOn:

Single sign-on (SSO) is a property of access control of multiple related, but independent software systems. With this property a user logs in once and gains access to all systems without being prompted to log in again at each of them.

i think theres some point.Why, we are not asked again to login although we have logged out? Its because on simulator the credential has been saved on safari(on the first time using facebook login, your app opens safari or facebook app if installed).

The information that allows you to see the 'you have already authorized...' message lies with Facebook.In order to revoke permissions from your app, you will need to touch the Graph API. FB docs, in the 'Delete' section of https://developers.facebook.com/docs/reference/api/user/

Revoking Login

You can also let people completely de-authorize an app, or revoke login, by making a call to this Graph API endpoint: DELETE /{user-id}/permissions

e.g in swift:

 let deletepermission = FBSDKGraphRequest(graphPath: "me/permissions/", parameters: nil, HTTPMethod: "DELETE")
        deletepermission.startWithCompletionHandler({(connection,result,error)-> Void in            
            println("the delete permission is \(result)")

        })

But in order to logout from the app completely so that user will be prompted to re-enter credentials,see below:

You have to logout from facebook app , then only you are truly logged out and then only the app again asks for credentials.It's because you are not logged anywhere on the phone.So,SSO rule doesnot apply here. If you are logging out only from your app (not the fb one) you will get logged because of logged in from safari in your case.Thats why, you will get the same message showing you are already authorized for this app.

Try testing on simulator, while you insert the credentials for the first time then safari opens and the credentials you enter saves in safari. So,next time when you logout and login app it doesnot ask for credentials.Because safari provides it(or facebook app if you have entered your credential there)

Now you open safari and open facebook. You see facebook has already open and the info it takes from the safari automatically or if you have facebook app installed then from there. So logout from safari and reopen your app and logout from the app.Then your app will ask again credentials.

Answer 2

This answer helped me determine the root cause issue. The 2 keys are SSO and Safari. Facebook poorly documents the Facebook Login process. I had to turn off SSO. This is on the Facebook Developer site, where your app is registered, under Settings. But more importantly is I had to change the behavior of the FBLoginManager to use UIWebView and not Safari. I did this with the following snippet:

FBSDKLoginManager *loginMgr = [[FBSDKLoginManager alloc] init];
loginMgr.loginBehavior = FBSDKLoginBehaviorWeb;

If you use the default behaviors it will manage logouts through the Facebook App or the browser Safari, and not directly from the App. The FBSDKLoginBehaviorWeb is to use iOS UIWebView in a popup. This works perfectly, and credentials are required each time after a logout.