Sharing facebook dialog by using UIImage as #"picture" - objective-c

Question

Here is simple code
UIImage *ScreenShot = [self getScreenshot];
NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:
#"Name", #"name",
#"Caption.", #"caption",
#"Description.", #"description",
#"www.example.com", #"link",
ScreenShot, #"picture",
nil];
[ facebook dialog:#"feed"
andParams:params
andDelegate:self];
And when I compile it get this message
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIImage length]: unrecognized selector sent to instance 0x1288bb90' *** First throw call stack:

Answer 1

You can't directly upload an image to the wall, when publishing to the wall you can just link an image to it.
So, you need to upload the UIImage somewhere first. You have 2 options:
Upload to your/some server and publish a wall post linking to it.
Upload to a facebook album. Check the graph API about doing that, it is pretty straightforward

Answer 2

I just had a look at the Facebook API in order to see what you are doing here. To my mind, this
http://www.facebook.com/dialog/feed?
app_id=123050457758183&
link=http://developers.facebook.com/docs/reference/dialogs/&
picture=http://fbrell.com/f8.jpg&
name=Facebook%20Dialogs&
caption=Reference%20Documentation&
description=Using%20Dialogs%20to%20interact%20with%20users.&
redirect_uri=http://www.example.com/response
clearly says what Facebook wants you to do. Do you see that the picture parameter is not an image itself but a link to an image? You'll have to upload the image first and then put the Link to the image into this parameter.
I'm not sure if this is the only error in your code but it's a major one for sure.

Answer 3

Import an image into your project and try to change the line UIImage *ScreenShot = [self getScreenshot] to : UIImage *ScreenShot = [UIImage imageNamed:#"yourimage.png"];
If it works, you may probably have problem in your "getScreenshot" method.
I use this for my app :
UIImage *ImageView = [UIImage imageNamed:#"anImage.png"];
NSMutableDictionary *params = [NSMutableDictionary dictionaryWithObjectsAndKeys:
ImageView, #"picture",#"Name", #"name",
nil];
//Let's post it
[facebook requestWithGraphPath:#"me/photos"
andParams:params
andHttpMethod:#"POST"
andDelegate:self];
-(void)request:(FBRequest *)request didLoad:(id)result{
if ([result objectForKey:#"id"]) {
UIAlertView *al = [[UIAlertView alloc] initWithTitle:#"MyApp" message:#"Your image has been posted on your wall!" delegate:self cancelButtonTitle:nil otherButtonTitles:#"OK", nil];
[al show];
[al release];
}
}