Developing iPhone Apps – how to get it right

Parker's Car Pricing Guide was a Top Ten Grossing App - and Top Twenty Paid App - in the UK App Store. It was also featured by Apple on iTunes - giving the App a very healthy sales boost!

Parker's Car Pricing Guide was a Top Ten Grossing App - and Top Twenty Paid App - in the UK App Store. It was also featured by Apple on iTunes - giving the App a very healthy sales boost!

We believe that a healthy portion of this success was due to the simple, polished, fun design of the App. I hope that others can benefit or take inspiration from the process that we followed, which is detailed below.

1. Application Definition Statement

The Application Definition Statement is the most valuable part of the App design process. It is a single sentence that describes what the App will do, who it is for, and what will differentiate it from its competitors. Its role is to keep a focus on why somebody would use your App.

"Parker’s makes it simple for the average car buyer to choose the best deal, wherever they are"

2. Concept

Once we had created our ADS we spent some time thinking through our basic concept. Apple categorises iPhone Apps into three distinct types, of which we chose to place Parker's in the third:

1. Immersive
2. Productivity
3. Utility

Parker's primary usage scenario is in a high pressure situation - allowing the car buyer to respond to a pushy second hand car salesman - so the App needed to enable fast access to a complicated database of information (price by manufacturer, model, year plate, mileage and options).

3. Wireframes

Wireframing the App was a process that took longer than everybody expected. However, as every good software engineer knows, spending more time planning means less rehashing later. One tricky issue was part exchange, as setting this up requires a number of interactions: enter your existing car, enter the car you want to buy, indicate you want to part exchange one for the other. We then needed to ensure that it would be easy for the user to reverse any state changes. Doing so would encourage the user to explore the interface and so discover advanced functions, much as in the excellent Tweetie.

The Wireframes were printed out neatly on large A3 sheets before being scrawled all over in marker pen!

Figure 1 - An early stage interaction diagram

We chose to model Parker's on Apple's Weather App - a well understood interface which puts a two dimensional dataset (cities/temperatures) at the users' fingertips, with functions to add/remove/reorder hidden behind the main screens. It translated well to our cars/prices dataset.

4. Pixel Perfect Designs

Creating pixel perfect designs is the most important phase for any brand stakeholders, as this is when they will finally get to see something resembling an iPhone App! Parker's was no exception, and a number of changes to colour palette and logo placement were made as a result.

We created strong car theme for the App. Items appear as though they are Top Trump cards, with backgrounds ranging from wooden trim to cracked black leather, and buttons look and act like vehicle radio buttons.

Figure 2 - Designs corresponding to Figure 1

After all the designs were signed off, we were finally ready to begin coding!

5. Delivery

The QA process for Parker's was stringent. We lost count of the number of times we ran through our test scripts! One gotcha was memory warnings, which would cause UIViewController classes to lose references to lazily initialised UIViews, often during the process of taking photos on the iPhone 3G. Repeated QA allowed us to prevent this issue occurring in any logic path.

We worked hard at enabling the App for social media. Buying a used vehicle is, by nature, a social process - one might ask acquaintances for their opinion on a purchase, or advertise a car for sale.

Whilst the product’s development consisted of a tremendous amount of hard work, the customer was very happy with the final result.



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About the author

Matthew Brooke-Smith
Matthew Brooke-Smith