Xcode calculations with multi-component picker
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I would like to set up a view controller with a 2-component picker where each side contains the same 7 objects. Each object carries the same value for both components. The user would make a selection from each side, enter a value in a provided text field (and optionally tap a "Calculate" button). A calculation would occur using that value and the values from the two picker component objects that were selected and the results would be displayed in a label.

For example, each picker contains the letters a - g. Each letter carries the value of 1 - 7 respectively, for each side of the picker. The user selects "b" and "d" and enters 10. The calculated result of 10 * 2 / 4 = 5 is displayed.

It sounds simple enough. I've found tutorials for doing calculations using values associated with a 1-component picker as well as working with 2-component pickers, but nothing for doing calculations with 2-component pickers. My experience with Xcode is somewhat short. So, feel free to go into detail.