We can share post in Facebook by using following steps:

Add one button on ViewController and give action to it.

Import #import <Social/Social.h>

Now in button action write following code.

 - (IBAction)facebookButtonAction:(id)sender {
    
    SLComposeViewController *controller = [SLComposeViewController
                                           composeViewControllerForServiceType:SLServiceTypeFacebook];
    SLComposeViewControllerCompletionHandler myBlock =
    ^(SLComposeViewControllerResult result){
        if (result == SLComposeViewControllerResultCancelled)
        {
            NSLog(@"Cancelled");
        }
        else
        {
            NSLog(@"Done");
        }
        [controller dismissViewControllerAnimated:YES completion:nil];
    };
    controller.completionHandler =myBlock;
    //Adding Text to the facebook post
    [controller setInitialText:@"My test post"];
    //Adding URL to the facebook post 
    [controller addURL:[NSURL URLWithString:@"http://www.test.com"]];
     
    [self presentViewController:controller animated:YES completion:nil];
    
    
}