The Core iOS Developer’s Cookbook, Fifth Edition

Data Source and Delegate Methods

Implement three key data source methods for your UIPickerView to make it function properly at a minimum level. These methods are as follows:

numberOfComponentsInPickerView:—Return the number of columns, as an integer.

pickerView:numberOfRowsInComponent:—Return the maximum number of rows per wheel, as an integer. The number of rows does not need to be identical. You can have one wheel with many rows and another with very few.

pickerView:titleForRow:forComponent or pickerView:viewForRow:forComponent: reusingView: ...