Open the Xcode game template if it's not already open, right-click on the Classes folder, select New Group, and rename the group to Assets.

Right-click on the Assets group and select New File....

Select Objective-C class and click on Next.

Enter AssetsDictionary in the name field, select NSObject from the Subclass of entry, and click on Next.

On the next dialog, click on Create.

Open the AssetsDictionary.h file.

Add an instance variable called _dict, which is a pointer to NSMutableDictionary, as shown in the following code:

@interface AssetsDictionary : NSObject {
    NSMutableDictionary *_dict;
}

Add a property called verbose, which is of type BOOL, as shown in the following code:

@property BOOL verbose;

Add an instance method called registerAsset, as shown in the following code:

-(id) registerAsset:(NSString *)name withContent:(id)content;

Add another instance method called unregisterAsset...