Added session expired error handling.

Summary: Whenever we call an API that returns a "session expired" error we
should clear the session data (acessToken / expiring date) and notify user about
it.

Test Plan: Login to app, then log out using www, then try calling rest / graph
method.

Reviewers: yariv, jimbru, brent, toddkrabach, jonathan

Reviewed By: yariv

CC: lshepard, yariv, kamil, brent, jonathan, toddkrabach

Differential Revision: 378197

sample/Hackbook/Hackbook/RootViewController.m

@@ -356,6 +356,22 @@ - (void)fbDidLogout {
     [self showLoggedOut];
 }
 
+/**
+ * Called when the session has expired.
+ */
+- (void)fbSessionInvalidated {   
+    UIAlertView *alertView = [[UIAlertView alloc]
+                              initWithTitle:@"Auth Exception" 
+                              message:@"Your session has expired." 
+                              delegate:nil 
+                              cancelButtonTitle:@"OK" 
+                              otherButtonTitles:nil, 
+                              nil];
+    [alertView show];
+    [alertView release];
+    [self fbDidLogout];
+}
+
 #pragma mark - FBRequestDelegate Methods
 /**
  * Called when the Facebook API request has returned a response. This callback
@@ -430,14 +446,6 @@ - (void)request:(FBRequest *)request didLoad:(id)result {
 - (void)request:(FBRequest *)request didFailWithError:(NSError *)error {
     NSLog(@"Err message: %@", [[error userInfo] objectForKey:@"error_msg"]);
     NSLog(@"Err code: %d", [error code]);
-
-    // Show logged out state if:
-    // 1. the app is no longer authorized
-    // 2. the user logged out of Facebook from m.facebook.com or the Facebook app
-    // 3. the user has changed their password
-    if ([error code] == 190) {
-        [self fbDidLogout];
-    }
 }
 
 @end

src/FBRequest.m

@@ -242,6 +242,7 @@ - (void)failWithError:(NSError *)error {
   if ([_delegate respondsToSelector:@selector(request:didFailWithError:)]) {
     [_delegate request:self didFailWithError:error];
   }
+  self.state = kFBRequestStateError;
 }
 
 /*
@@ -355,7 +356,9 @@ - (void)connectionDidFinishLoading:(NSURLConnection *)connection {
   self.responseText = nil;
   self.connection = nil;
 
-  self.state = kFBRequestStateComplete;
+  if (self.state != kFBRequestStateError) {
+    self.state = kFBRequestStateComplete;
+  }
 }
 
 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {

src/Facebook.h

@@ -110,4 +110,13 @@
  */
 - (void)fbDidLogout;
 
-@end
+/**
+ * Called when the current session has expired. This might happen when:
+ *  - the access token expired 
+ *  - the app has been disabled
+ *  - the user revoked the app's permissions
+ *  - the user changed his or her password
+ */
+- (void)fbSessionInvalidated;
+
+@end

src/Facebook.m

@@ -30,7 +30,7 @@
 static NSString* kSDK = @"ios";
 static NSString* kSDKVersion = @"2";
 
-static NSString *requestFinishedKeyPath = @"finished";
+static NSString *requestFinishedKeyPath = @"state";
 static void *finishedContext = @"finishedContext";
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
@@ -122,6 +122,19 @@ - (void)dealloc {
   [super dealloc];
 }
 
+- (void)invalidateSession {
+  self.accessToken = nil;
+  self.expirationDate = nil;
+
+  NSHTTPCookieStorage* cookies = [NSHTTPCookieStorage sharedHTTPCookieStorage];
+  NSArray* facebookCookies = [cookies cookiesForURL:
+                                [NSURL URLWithString:@"http://login.facebook.com"]];
+
+  for (NSHTTPCookie* cookie in facebookCookies) {
+    [cookies deleteCookie:cookie];
+  }
+}
+
 /**
  * A private helper function for sending HTTP requests.
  *
@@ -161,6 +174,12 @@ - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(N
   if (context == finishedContext) {
     FBRequest* _request = (FBRequest*)object;
     FBRequestState requestState = [_request state];
+    if (requestState == kFBRequestStateError) {
+      [self invalidateSession];
+      if ([self.sessionDelegate respondsToSelector:@selector(fbSessionInvalidated)]) {
+        [self.sessionDelegate fbSessionInvalidated];
+      }
+    }
     if (requestState == kFBRequestStateComplete || requestState == kFBRequestStateError) {
       [_request removeObserver:self forKeyPath:requestFinishedKeyPath];
       [_requests removeObject:_request];
@@ -388,22 +407,11 @@ - (BOOL)handleOpenURL:(NSURL *)url {
  * settings screen on facebook.com.
  */
 - (void)logout {
-    [_accessToken release];
-    _accessToken = nil;
-    [_expirationDate release];
-    _expirationDate = nil;
-
-    NSHTTPCookieStorage* cookies = [NSHTTPCookieStorage sharedHTTPCookieStorage];
-    NSArray* facebookCookies = [cookies cookiesForURL:
-                                [NSURL URLWithString:@"http://login.facebook.com"]];
+  [self invalidateSession];
 
-    for (NSHTTPCookie* cookie in facebookCookies) {
-        [cookies deleteCookie:cookie];
-    }
-
-    if ([self.sessionDelegate respondsToSelector:@selector(fbDidLogout)]) {
-        [self.sessionDelegate fbDidLogout];
-    }
+  if ([self.sessionDelegate respondsToSelector:@selector(fbDidLogout)]) {
+    [self.sessionDelegate fbDidLogout];
+  }
 }
 
 /**