UITabBarController中的“重用” UITableViewController

Question

So I started to work on an app, it has 5 tabs of which 3 shows UITableViewController with custom cells, but with different data.

Is it possible to link 3 tabs to same UITableViewController, but check which tab is selected, and according to that, load right data?

I tried putting in UITableViewController:

if (self.tabBarController.selectedIndex == 0)
//Load array1
else if (self.tabBarController.selectedIndex == 1)
//Load array2
else
//Load array3

But the indexes are not always the same (it depends in which order you select tabs?, and sometimes I get index that is very high number).

How would you do this?

Answer 1

Assuming you mean "Is it possible to link 3 tabs to same UITableViewController instance ":

It is possible, but it's not a great idea. I believe (but couldn't point you at chapter and verse) that the assumption by Apple is that different tabs will have unique, different view controller instances in them. When you change tabs, the view controller instance about to hide has various 'about to be hidden' lifecycle methods called on it. Likewise, the view controller instance about to appear has various 'about to be shown' lifecycle methods shown on it. It's possible your single view controller instance may fall foul of the order of these lifecycle methods being shown.

The above point aside, it's also a waste of effort reloading a table each time just because the user changed a tab. Be kind and do things the way you're meant to do them. There's no reason you can't have a single view controller class that handles everything, but you create a different instance of it for each tab.

Note: your UIViewController being aware of which tab it is in counts as a 'code smell'. This usually means you're doing something in an undesirable fashion and hurting the re-usability of this code. That applies in this case.

To avoid this 'code smell', your view controller should be able to be given the data it is to show, without any knowledge of even being shown in a UITabBarController.

Answer 2

Leverage the UITabBarControllerDelegate to detect when the user switches tabs.

Upon tab switch:

• assign the new array contents to a member variable used to display the data in the table view (with a similar if/else block as you posted), and
• call reloadData on your UITableView to trigger a redraw with the data