ok, I've read tons of bits and pieces on the subject of loading dynamic content (from the web) into a UITableView and the problem with calculating cell height upfront. I've tried different simple implementations but the problem persists...

Assuming I need to read a JSON file from the web, parse it into 'item' objects, each with variable size image and various text labels, here is what I believe would be the right approach to avoid long hang time of the app while everything is loading:

1. on app load read JSON file and parse into items array
2. provide only small part of the items array to the tableview (about 10 items) - since I need to load the images associated with each item to calculate cell height - I don't want the view to go through the whole items list and load all images - this hangs the app until every image is loaded
3. display the tableview with the available cells (assuming I load a few 'spare' ones, user can even scroll to more items)
4. in the background using Grand Central Dispatch download images for all/some of the remaining items and then reload the tableview with the new data (repeat step 4 if item list is very long)

Step 2 above is necessary since I have no way to calculate the cell height without loading the images first, and since tableview first calculates height of all cells it may take a very long time to download all images for all items.

Would you say this is the right approach? am I missing something?