How do I create a text field or label that resizes based on how much text is in it? [duplicate]

This question already has answers here: Closed 开发者_JS百科10 years ago.

Possible Duplicate:

How do I wrap text in a UITableViewCell without a custom cell

I've seen at least one application that uses a grouped UITableView with a cell containing paragraphs of text, and the cell is taller or shorter based on the length of the text, but I don't quite get how this is done.

How does one, given a variable width font, figure out how high a UITextField or something needs to be in order to display all of the text contained in it without reducing the point size of the font?

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See Apple's documentation about NSString additions for the iPhone to read about which methods to use to calculate these metrics.