Facebook SDK iOS中的电子邮件访问为空？

Question

    - (void)facebookViewControllerDoneWasPressed:(id)sender {

NSLog(@"FACEBOOK VIEW CONTROLLER");


NSMutableString *text = [[NSMutableString alloc] init];

// we pick up the users from the selection, and create a string that we use to update the text view
// at the bottom of the display; note that self.selection is a property inherited from our base class
for (id<FBGraphUser> user in self.friendPickerController.selection) {
    if ([text length]) {
        [text appendString:@", "];
    }
    [text appendString:user.name];

    //[user objectForKey:@"email"];

 //   [text appendFormat:[user objectForKey:@"email"]];


    NSLog(@"EMAIL IS %@", [user objectForKey:@"email"]);

}

   // [self fillTextBoxAndDismiss:text.length > 0 ? text : @"Email"];

[self fillTextBoxAndDismiss:text];


}

我想获取朋友列表的电子邮件地址。

我得到了FBGraphUser用户，但它没有给我发回电子邮件

我尝试了这个，但它返回null。

           NSLog(@"EMAIL IS %@", [user objectForKey:@"email"]);

此处电子邮件为空，是否可以访问我朋友的电子邮件？