title: Error objective-c IN APP PURCHASE implementation
body: <p>I'm implementing the IN APP PURCHASE and I'm not a very experienced developer.
  I'm using the brant troy tutorial I found here:
  <a href="http://troybrant.net/blog/2010/01/in-app-purchases-a-full-walkthrough/comment-page-4/#comment-11008" rel="nofollow">Tutorial</a></p>
  
  <p>I have the error in loadStore method implementation:
  Sending ‘InAppPurchaseManager *const __strong’ to parameter of incompatible type ‘id’</p>
  
  <pre><code>//
  //  InAppPurchaseManager.h
  //
  
  #import &lt;Foundation/Foundation.h&gt;
  #import &lt;StoreKit/StoreKit.h&gt;
  
  @interface InAppPurchaseManager : NSObject &lt;SKProductsRequestDelegate&gt;
  {
      SKProduct *proUpgradeProduct;
      SKProductsRequest *productsRequest;
  }
  
  // public methods
  - (void)loadStore;
  - (BOOL)canMakePurchases;
  - (void)purchaseProUpgrade;
  
  @end
  
  ---
  
  #import "InAppPurchaseManager.h"
  
  #define kInAppPurchaseProUpgradeProductId @"com.user.app.product"
  
  @implementation InAppPurchaseManager
  
  - (void)loadStore
  {
      // restarts any purchases if they were interrupted last time the app was open
  
      [[SKPaymentQueue defaultQueue] addTransactionObserver: self];
  ERROR HERE: Sending 'InAppPurchaseManager *const __strong' to parameter of incompatible type 'id&lt;SKPaymentTransactionObserver&gt;'
  
      // get the product description (defined in early sections)
      [self requestProUpgradeProductData];
  }
  
  @end
  </code></pre>
  
  <p>Can anyone help me?</p>