Passing an objective-c protocol delegate as a parameter

When I pass the objective-c protocol as a parameter, when this delegate is then used to run one of its methods, the method fails.

I am using a delegate from the Paypal iOS SDK, which is defined like this:

@protocol PayPalPaymentDelegate <NSObject>
    - (void)payPalPaymentDidCancel:(PayPalPaymentViewController *)paymentViewController;
@end

      

        
        
        
      

    

I have a UIViewController that implements the protocol:

//simpleviewcontroller.h
@interface SimpleViewController : UIViewController<PayPalPaymentDelegate>

      

        
        
        
      

    

and method signatures like:

// HelperFunctions.m
+ (void) doSomething: (id<PayPalPaymentDelegate>)paypalDelegate
{
    // the selector 'payPalPaymentDidCancel' DOES fire
    [paypalDelegate performSelector:@selector(payPalPaymentDidCancel:) withObject:self]
}


// called from simpleviewcontroller.m that implements PayPalPaymentDelegate
[HelperFunctions doSomething: self]

      

        
        
        
      

    

The problem is that when paypal returns the result, it doesn't call the delegate:

// code inside of the 'success' block of an AFNetworking call
PayPalPaymentViewController *paymentViewController;
paymentViewController = [[PayPalPaymentViewController alloc] initWithPayment:payment    
                                                             configuration:paypalConfiguration   
                                                             delegate:paypalDelegate];

      

        
        
        
      

    

PaypalDelegate passed to 'delegate' never starts paypal here. Whereas it starts if executed with simpleviewcontroller.m and not with the doSomething method