Tippy is a tip calculator application for iOS.
Submitted by: Nandini Bhattacharya
Time spent:12 hours spent in total
The following required functionality is complete:
- User can enter a bill amount, choose a tip percentage, and see the tip and total values.
- Settings page to change the default tip percentage.
The following optional features are implemented:
- UI animations -> Basic fade in, just as proof of concept
- Remembering the bill amount across app restarts (does not reset after 10 minutes yet)
- Using locale-specific currency and currency thousands separators.
- Making sure the keyboard is always visible and the bill amount is always the first responder. This way the user doesn't have to tap anywhere to use this app. Just launch the app and start typing.
The following additional features are implemented:
- Clear Button
- Added UIPickerView Control
- Dark and Light Theme Handling
- Theme class
Here's a walkthrough of implemented user stories:
GIF created with LiceCap.
As part of your pre-work submission, please reflect on the app and answer the following questions below:
Question 1: "What are your reactions to the iOS app development platform so far? How would you describe outlets and actions to another developer? Bonus: any idea how they are being implemented under the hood? (It might give you some ideas if you right-click on the Storyboard and click Open As->Source Code")
Answer: For someone who has never used the Swift or iOS platform, this was a fairly easy platform to ramp up on with reasonable documentation and great tutorials. To me outlets are a way to reference the View UI objects from the Controller. Basically the allow the plumbing of the view objects properties so that the controller can either react to changes of the proerties or manipulate the view object properties. Actions are effectively events that are generated in response to a user interaction with the UI objects.
Within the main.storyboard xml, the TipViewController is associated via an ID with the view as a target for the view. Within the UI object markup code eg the segmentSelector, the controller object is set as the destination for the event, so that when the event is generated, it is routed to the right method within the Controller.
Question 2: "Swift uses Automatic Reference Counting (ARC), which is not a garbage collector, to manage memory. Can you explain how you can get a strong reference cycle for closures? (There's a section explaining this concept in the link, how would you summarize as simply as possible?)"
Answer: Strong reference cycles are created when a class instance holds a strong reference to another class instance while that class instance in turns holds a reference to the former class, resulting in a cyclic reference. In case of a closure, if a class has a closure as a property, then the class instance will hold a strong reference to the closure stored in the property. The closure implicitly captures properties of the class, and thus a strong reference to the class instance. This will result in strong reference cycle.
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