iPhone SDK: Using Facebook Connect for iPhone, Working with Extended Permissions Part 2 of 2

Posted by Tim Stephenson, RaddOnline® on Sunday, March 22, 2009

Clearing Up UI Confusion

In part one, I describe using the Facebook Connect for iPhone SDK. In the sample application provided by Facebook, a Get Permission button checks to see if the user has granted the appropriate extended permission to the application. It is a permission to post status updates. The permission needs to be granted only once. If the user clicks the button after permission is granted, they see this message: You have already granted this permission to the application. This begs the question, why display the button after permission is granted?

I’ll provide a sample project at the end of the article. Facebook updates the SDK frequently, be sure to get the latest version from the Facebook site. Facebook Connect for iPhone

Plan of Action

The documentation describes the process for working with the API, and provides two samples of interest:

- (void)getUserName { 
    NSString* fql = @"select name from user where uid == 1234"; 
    NSDictionary* params = [NSDictionary dictionaryWithObject:fql forKey:@"query"]; 
    [[FBRequest requestWithDelegate:self] call:@"facebook.fql.query" params:params]; 
} 
- (void)request:(FBRequest*)request didLoad:(id)result { 
    NSArray* users = result; 
    NSDictionary* user = [users objectAtIndex:0]; 
    NSString* name = [user objectForKey:@"name"]; 
    NSLog(@"Query returned %@", name); 
}

And

-(void)setUsersStatus { 
    NSString *statusString = exampleTextField.text; 
    NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys: statusString, @"status", @"true", @"status_includes_verb", nil]; 
    [[FBRequest requestWithDelegate:self] call:@"facebook.Users.setStatus" params:params]; 
}

Either works. In the first method, replace the FQL with:

select status_update from permissions where uid == 1234

In the second example, use the Users.hasAppPermission method to confirm if the user has opted into the extended permission. Read more about this method here. Users.hasAppPermission

For my example, I’ve decided to go with the first approach. In either case, use this delegate method to process the request:

 - (void)request:(FBRequest*)request didLoad:(id)result

The SessionViewController in the sample project is using this method to handle the request used to retrieve the user’s name:

- (void)request:(FBRequest*)request didLoad:(id)result {
  NSArray* users = result;
  NSDictionary* user = [users objectAtIndex:0];
  NSString* name = [user objectForKey:@"name"];
  _label.text = [NSString stringWithFormat:@"Logged in as %@", name];
}

To avoid confusion with this code, and to make it easier to reuse in other projects, I’ll create a class with the sole purpose of tracking the update status permission.

Creating the Permission Status Class

Open the project in the fbconnect-iphone/samples/Connect folder by double clicking the Connect.xcodeproj file.

1. Right click on the Source group and select Add => New File.
2. Select Cocoa Touch Classes => NSObject subclass and then click Next.
3. Name the file PermissionStatus.m and be sure to check the Also Create “PermissionStatus.h” check box.
4. Open the PermissionStatus.h file and make it look like this:

#import <Foundation/Foundation.h>
#import "FBRequest.h" 

@protocol PermissionStatusDelegate;

@interface PermissionStatus : NSObject <FBRequestDelegate> {
    BOOL userHasPermission;
    id<PermissionStatusDelegate> delegate;
}

@property (nonatomic, assign) BOOL userHasPermission;
@property (nonatomic, retain) id<PermissionStatusDelegate> delegate;

- (PermissionStatus *)initWithUserId:(long long int)uid;

@end

#pragma mark method to call after response
@protocol PermissionStatusDelegate <NSObject>
- (void)statusWasSet:(BOOL)status;
@end

There are a few items of interest here.

1. It imports the FBRequest.h header file.
2. It implements the FBRequestDelegate protocol.
3. It defines a protocol of its own, ”@protocol PermissionStatusDelegate;” that can be used to determine the result of the status check.
4. It contains a property where the delegate can be set.

Next, implement the class as defined in the interface. Open PermissionStatus.m and mimic this:

#import "PermissionStatus.h" 

@implementation PermissionStatus
@synthesize userHasPermission;
@synthesize delegate;

- (PermissionStatus *)initWithUserId:(long long int)uid { 
    self = [super init];

    if (self) {
        NSString* fql = [NSString stringWithFormat:
                         @"select status_update from permissions where uid == %lld", uid]; 
        NSDictionary* params = [NSDictionary dictionaryWithObject:fql forKey:@"query"]; 
        [[FBRequest requestWithDelegate:self] call:@"facebook.fql.query" params:params]; 
        userHasPermission = NO;
    }
    return self;
} 

#pragma mark FBRequestDelegate
- (void)request:(FBRequest*)request didLoad:(id)result {
    NSArray *permissions = result;
    NSDictionary *permission = [permissions objectAtIndex:0];
    userHasPermission = [[permission objectForKey:@"status_update"] boolValue];
    [delegate statusWasSet:userHasPermission];
}

@end

How it works

In the initWithUserId: method, you define the FQL to retrieve the extended permission and add it to the params dictionary. Instantiate the FBRequest with the PermissionStatus instance as the delegate. I set the userHasPermission property to NO just in case an error occurs with the request. I don’t care to report any errors, it returns NO if something went wrong. To report an error, use the request:didFailWithError: method to catch the error.

In the request:didLoad: method I retrieve the result and call our new delegate method statusWasSet: with the value of the response.

Using the PermissionStatus Class to Hide the Get Permission Button.

First, open SessionViewController.h and make these changes:

1. Import the new class:

   #import "PermissionStatus.h"

2. Set SessionViewController as a delegate for our class:

   <FBDialogDelegate, FBSessionDelegate, FBRequestDelegate, PermissionStatusDelegate>

3. Add a property to hold an instance of the PermissionStatus class:

@interface SessionViewController : UIViewController
    <FBDialogDelegate, FBSessionDelegate, FBRequestDelegate, PermissionStatusDelegate> {
        IBOutlet UILabel* _label;
        IBOutlet UIButton* _permissionButton;
        IBOutlet UIButton* _feedButton;
        IBOutlet FBLoginButton* _loginButton;
        FBSession* _session;
        PermissionStatus *permissionStatusForUser;
}

@property(nonatomic,readonly) UILabel* label;
@property (nonatomic, retain) PermissionStatus *permissionStatusForUser;

The Implementation

A few more steps remain to complete the task. Open the SessionViewController.m file and make these changes:

Synthesize the property to hold the instance of PermissionStatus

@synthesize permissionStatusForUser;

Use the dialogDidSucceed: method in the FBDialogDelegate protocol to hide the button if the permission dialog succeeds.

- (void)dialogDidSucceed:(FBDialog*)dialog { 
    _permissionButton.hidden = YES;
}

Look for the FBSessionDelegate section and instantiate the PermissionStatus class in the session:didLogin: method

// FBSessionDelegate

- (void)session:(FBSession*)session didLogin:(FBUID)uid {
    //_permissionButton.hidden = NO;
    _feedButton.hidden = NO;

    NSString* fql = [NSString stringWithFormat:
        @"select uid,name from user where uid == %lld", session.uid];

    NSDictionary* params = [NSDictionary dictionaryWithObject:fql forKey:@"query"];
    [[FBRequest requestWithDelegate:self] call:@"facebook.fql.query" params:params];

        //Instantiate the PermissionStatus class with the user id.
    permissionStatusForUser = [[PermissionStatus alloc] initWithUserId:session.uid];
    permissionStatusForUser.delegate = self;
}

Implement the statusWasSet: delegate method and set the hidden property of the button to match the status. When done, release the object.

#pragma mark RAD PermissionStatusDelegate
- (void)statusWasSet:(BOOL)status {
    _permissionButton.hidden = status;
    [permissionStatusForUser release];
}

Build and run the application. The Get Permission button hides if permission was previously granted. If not, it remains visible.

Here is the sample file. I’ve removed the API Keys and Template Bundle IDs. Just add the appropriate IDs and enjoy. fbconnect-iphone.zip

Post a comment

Name (required)

Email Address (required, but not displayed)

Web Address

Comment (required)

Recent Entries

• Ruby on Rails: Using Exchange Web Services from a Rails App
  Posted by Tim Stephenson
  RaddOnline™
  Mar 23, 2010
• iPhone SDK: Testing Network Reachability
  Posted by Tim Stephenson
  RaddOnline™
  Apr 24, 2009
• iPhone SDK: UINavigationController, Hiding the Navigation Bar
  Posted by Tim Stephenson
  RaddOnline™
  Apr 03, 2009
• iPhone SDK: Using Facebook Connect for iPhone, Working with Extended Permissions Part 2 of 2
  Posted by Tim Stephenson
  RaddOnline™
  Mar 22, 2009
• iPhone SDK: Using Facebook Connect for iPhone Part 1 of 2
  Posted by Tim Stephenson
  RaddOnline™
  Mar 21, 2009
• iPhone SDK: Resizing a UITableViewCell to Hold Variable Amounts of Text, Part 2 of 2
  Posted by Tim Stephenson
  RaddOnline™
  Mar 14, 2009
• iPhone SDK: Using a UITableViewCell with a UITextView for Entering Text, Part 1 of 2
  Posted by Tim Stephenson
  RaddOnline™
  Mar 07, 2009
• iPhone SDK: UITabBarController, How to Save User Customized Tab Order
  Posted by Tim Stephenson
  RaddOnline™
  Feb 27, 2009
• iPhone SDK: Creating a Modal Tab Bar Controller
  Posted by Tim Stephenson
  RaddOnline™
  Feb 20, 2009
• Improving SEO With XML Site Mapping
  Posted by Tim Stephenson
  RaddOnline™
  Feb 13, 2009
• Ruby on Rails: Testing Net::HTTP With Mocks
  Posted by Tim Stephenson
  RaddOnline™
  Jan 07, 2009