This is a simple tip calculator to assist users with calculating and splitting bills.

Time spent: 8-9 hours in total

• Required: User can input a bill amount and see both the tip amount and total amount for three different tip percentages.
• Required: User can go to the settings page and change their three standard tip amounts (for bad, average, and great service, respectively). These modified tip amounts will persist across sessions.
• Optional: The app remembers the bill amount used most recently, except when the app was not used in the last 10 minutes.
• Optional: The app also includes a feature for groups to determine the amount each person should pay to split the bill.
• Optional: The app automatically updates all data while the user is typing.
• Optional: The app works flawlessly across different locales and handles commas, periods, and currency symbols correctly.
• Optional: Everything is purple ;)

I chose to increase the font size of the bill amount since it's the only number the user actually inputs. I also moved the tip selector up higher to be right under the actual tip amount.

For the settings I chose to allow the user to change his/her default tip percentages, since I felt this was the setting where people would most likely have different preferences.

I spent the longest time on getting the calculator to work perfectly with any locale/currency. My eventual solution involved using an NSNumberFormatter in NSNumberFormatterCurrencyStyle mode with lenient set to YES. Using this actually enabled me to set up functions to parse numerical amounts out of strings and convert numbers into monetary strings. These functions ended up being extremely useful within my code, since they abstracted out most of the dirty work. (In general, I tried to abstract out redundant code wherever possible.)

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