Question

So I am working on a tip calculator as my first self guided iOS app and I want to be able to output to the UILabel that shows the bill with currency format. As an example, user presses 1, label shows $0.01, user then enters 2, label shows $0.12, user enters 3, label shows $1.23 and so on. Currently I am getting input and updating the display from UIButton’s that have the numbers on them like this:
NSString *digit = sender.currentTitle;
self.display.text = [self.display.text stringByAppendingString:digit];

I have read several questions on here about number formatting and tried the solutions but cannot get anything to work, but most of the solutions were for UITextFields, so I am thinking perhaps there is a problem with how I am getting input? Any help would be greatly appreciated.

*to clarify, what I am going for is speed. I have a decimal button and have the display with the $ sign, but I want to get rid of the decimal button so all the user has to do is punch in the numbers and not even worry about putting the decimal.

Answer 1

Here’s an idea, why not store the number in cents/pennies – i.e the smallest possible value for a currency. That way if the user presses another number you can simply multiply the existing number by 10 and add the new number.

An example:

• User presses 1 => Number was 0 before, so new number is 0 * 10 + 1 =
  1
• User presses 2 => Number was 1 before, so new number is 1 * 10 + 2 =
  12
• User presses 3 => Number was 12 before, so new number is 12 * 10 + 3
  = 123

Now to display this, all you have to do is divide the number by 100 (or whatever is suitable for the given currency) and use the result in a string with format %0.01f