RollTide73 RollTide73 - 3 months ago 19
iOS Question

When to use dequeueReusableCellWithIdentifier vs dequeueReusableCellWithIdentifier : forIndexPath

There are two overloads for dequeueReusableCellWithIdentifier and I'm trying to determine when should I use one vs the other?

The apple docs regarding the forIndexPath function states, "This method uses the index path to perform additional configuration based on the cell’s position in the table view."

I'm not sure how to interpret that though?

Answer

The most important difference is that the forIndexPath: version asserts (crashes) if you didn't register a class or nib for the identifier. The older (non-forIndexPath:) version returns nil in that case.

You register a class for an identifier by sending registerClass:forCellReuseIdentifier: to the table view. You register a nib for an identifier by sending registerNib:forCellReuseIdentifier: to the table view.

If you create your table view and your cell prototypes in a storyboard, the storyboard loader takes care of registering the cell prototypes that you defined in the storyboard.

Session 200 - What's New in Cocoa Touch from WWDC 2012 discusses the (then-new) forIndexPath: version starting around 8m30s. It says that “you will always get an initialized cell” (without mentioning that it will crash if you didn't register a class or nib).

The video also says that “it will be the right size for that index path”. Presumably this means that it will set the cell's size before returning it, by looking at the table view's own width and calling your delegate's tableView:heightForRowAtIndexPath: method (if defined). This is why it needs the index path.

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