Question

I have a situation, where i load a facebook feed,and depending upon the post type (video/image/link etc), i create corresponding classes. Each post type has a different corresponding model class and view class, however there is only one controller class which is instantiated for each post.
Now i need a way of dynamically deciding which model and view classes to create inside the controller for a particular post type. Right now, i have a creation helper class, which returns the corresponding model and view classes depending upon the post type. But it seems like a messy way of doing things. If have 20 something post types, thats 20 something if statements.

Is there a better way of doing this ?

Answer 1

You could keep a map (of sorts) of the post types against the classname used to handle the types:

static struct
{
    PostType type;         // A typedef'd enum with POST_TYPE_ONE, ...
    NSString *classname;
} _handlers[] = 
{
    { POST_TYPE_ONE, @"OneHandler" },
    { POST_TYPE_TWO, @"TwoHandler" },
    ....
    { POST_TYPE_TWENTY, @"TwentyHandler" }
};

const NSUInteger NUM_HANDLERS = sizeof(_handlers) / sizeof(_handlers[0]);

And then instantiate the class instance using:

id handler = nil;
for (NSUInteger index = 0; index < NUM_HANDLERS && handler == nil; index++)
{
    if (postType == _handlers[index].postType)
    {
        handler = [[ NSClassFromString(_handlers[index].classname) alloc ] init];
    }
}

Or if you can guarantee that postType will always be between 0 and 19, can just keep an array of classnames and use:

id handler = [[ NSClassFromString(_handlers[postType] alloc ] init];

You should ensure all handler classes derive from a common base class, to provide common functionality.