Now that you’re ready to become a software developer and have read the introduction of this book, you need to become familiar with several key concepts. Your computer program will do exactly what you tell it to do—no more and no less. It will follow the programming rules that were defined by the operating system and the Swift programming language. Your program doesn’t care if you are having a bad day or how many times you ask it to perform something. Often, what you think you’ve told your program to do and what it actually does are two different things.

Depending on your background, working with something absolutely black and white may be frustrating. Many times, programming students have lamented, “That’s not what I wanted it to do!” As you begin to gain experience and confidence in programming, you’ll begin to think like a programmer. You will understand software design and logic, and you will experience having your programs perform exactly as you want and the satisfaction associated with this.

Thinking Like a Developer

Software development involves writing a computer program and then having a computer execute that program. A computer program is the set of instructions that you want the computer to perform. Before beginning to write a computer program, it is helpful to list the steps that you want your program to perform in the order you want them accomplished. This step-by-step process is called an algorithm.

If you want to write a computer program to toast a piece of bread, you would first write an algorithm. This algorithm might look something like this:

1. Take the bread out of the bag.
2. Place the bread in the toaster.
3. Press the toast button.
4. Wait for the toast to pop up.
5. Remove the toast from the toaster.

At first glance, this algorithm seems to solve the problem. However, the algorithm leaves out many details and makes many assumptions. Here are some examples:

• What kind of toast does the user want? Does the user want white bread, wheat bread, or some other kind of bread?
• How does the user want the bread toasted? Light or dark?
• What does the user want on the bread after it is toasted: butter, margarine, honey, or strawberry jam?
• Does this algorithm work for all users in their cultures and languages? Some cultures may have another word for toast or not know what toast is.

Now, you might be thinking this is getting too detailed for making a simple toast program. Over the years, software development has gained a reputation of taking too long, costing too much, and not being what the user wants. This reputation came to be because computer programmers often start writing their programs before they have actually thought through their algorithms.

The key ingredients to making successful applications are design requirements. Design requirements can be formal and detailed or simple like a list on a piece of paper. Design requirements are important because they help the developer flesh out what the application should do and not do when complete. Design requirements should not be completed in a programmer’s vacuum, but should be produced as the result of collaboration between developers, users, and customers.

Another key ingredient to your successful app is the user interface (UI) design. Apple recommends you spend more than 50 percent of the entire development process focusing on the UI design. The design can be done using simple pencil and paper or using Xcode’s storyboard feature to lay out your screen elements. Many software developers start with the UI design, and after laying out all the screen elements and having many users look at paper mock-ups, they then write the design requirements from their screen layouts.

After you have done your best to flesh out all the design requirements, laid out all the user interface screens, and had the clients or potential customers look at your design and give you feedback, you can begin coding. Once coding begins, design requirements and user interface screens can change, but the changes are typically minor and easily accommodated by the development process. See Figures 1-1 and 1-2.

Figure 1-1 shows a mock-up of a mobile banking app screen prior to development. Developing mock-up screens along with design requirements forces developers to think through many of the application’s usability issues before coding begins. This enables the application development time to be shortened and makes for a better user experience and better reviews on the App Store. Figure 1-2 shows how the view for the mobile banking app appears when completed.

Completing the Development Cycle

Now that you have the design requirements and user interface designs and have written your program, what’s next? After programming, you need to make sure your program matches the design requirements and user interface design and ensure that there are no errors. In programming vernacular, errors are called bugs. Bugs are undesired results of your programming and must be fixed before the app is released to the App Store. The process of finding bugs in programs and making sure the program meets the design requirements is called testing. Typically, someone who is experienced in software testing methodology and who didn’t write the app performs this testing. Software testing is commonly referred to as quality assurance (QA).

During the testing phase, the developer will need to work with the QA staff to determine why the application is not working as designed. The process is called debugging. It requires the developer to step through the program to find out why the application is not working as designed. Figure 1-3 shows the complete software development cycle.

Frequently during testing and debugging, changes to the requirements (design) must occur to make the application more usable for the customers. After the design requirements and user interface changes are made, the process starts again.

At some point, the application that everyone has been working so hard on must be shipped to the App Store. Many considerations are taken into account as to when in the cycle this happens:

• Cost of development
• Budget
• Stability of the application
• Return on investment

There is always the give and take between developers and management. Developers want the app to be perfect, and management wants to start realizing revenue from the investment as soon as possible. If the release date were left up to the developers, the app would likely never ship to the App Store. Developers would continue to tweak the app forever, making it faster, more efficient, and more usable. At some point, however, the code needs to be pried from the developers’ hands and uploaded to the App Store so it can do what it was meant to do.

Introducing Object-Oriented Programming

As discussed in detail in the introduction, playgrounds enable you to focus on object-oriented programming (OOP) without having to cover all the Swift programming syntax and complex Xcode development environment in one big step. Instead, you can focus on learning the basic principles of OOP and using those principles quickly to write your first programs.

For decades, developers have been trying to figure out a better way to develop code that is reusable, manageable, and easily maintained over the life of a project. OOP was designed to help achieve code reuse and maintainability while reducing the cost of software development.

OOP can be viewed as a collection of objects in a program. Actions are performed on these objects to accomplish the design requirements.

An object is anything that can be acted on. For example, an airplane, person, or screen/view on the iPad can all be objects. You may want to act on the plane by making the plane bank. You may want the person to walk or to change the color of the screen of an app on the iPad.

Playgrounds execute your code as you complete each line, such as the one shown in Figure 1-4. When you run your playground applications, the user can apply actions to the objects in your application. Xcode is an integrated development environment (IDE) that enables you to run your application from within your programming environment. You can test your applications on your computer first before running them on your iOS devices by running the apps in Xcode’s simulator, as shown in Figure 1-5.

Actions that are performed on objects are called methods. Methods manipulate objects to accomplish what you want your app to do. For example, for a jet object, you might have the following methods:

goUp
goDown
bankLeft
turnOnAfterburners
lowerLandingGear

The table object in Figure 1-5 is actually called UITableView when you use it in a program, and it could have the following methods:

numberOfRowsInSection
cellForRowAtIndexPath
canEditRowAtIndexPath
commitEditingStyle
didSelectRowAtIndexPath

Most objects have data that describes those objects. This data is defined as properties. Each property describes the associated object in a specific way. For example, the jet object’s properties might be as follows:

altitude = 10,000 feet
heading = North
speed = 500 knots
pitch = 10 degrees
yaw = 20 degrees
latitude = 33.575776
longitude = -111.875766

For the UITableView object in Figure 1-5, the following might be the properties:

backGroundColor = Red
selectedRow = 3
animateView = No

An object’s properties can be changed at any time when your program is running, when the user interacts with the app, or when the programmer designs the app to accomplish the design requirements. The values stored in the properties of an object at a specific time are collectively called the state of an object.

State is an important concept in computer programming. When teaching students about state, we ask them to go over to a window and find an airplane in the sky. We then ask them to snap their fingers and make up some of the values that the plane’s properties might have at that specific time. Those values might be as follows:

altitude = 10,000 feet
latitude = 33.575776
longitude = -111.875766

Those values represent the state of the object at the specific time that they snapped their fingers.

After waiting a couple minutes, we ask the students to find that same plane, snap their fingers again, and record the plane’s possible state at that specific point in time.

The values of the properties might then be something like the following:

altitude = 10,500 feet
latitude = 33.575665
longitude = -111.875777

Notice how the state of the object changes over time.

Working with the Playground Interface

Playgrounds offer a great approach in using the concepts just discussed without all the complexity of learning Xcode and the Swift language at the same time. It takes only a few minutes to familiarize yourself with the playground interface and begin writing a program.

Technically speaking, the playground interface is not a true IDE like you will be using to write your iOS apps, but it is pretty close and much easier to learn in. A true IDE combines code development, user interface layout, debugging tools, documentation, and simulator/console launching for a single application; see Figure 1-6. However, playgrounds offer a similar look, feel, and features to the Xcode IDE you develop apps with.

In the next chapter, you will go through the playground interface and write your first program.

Summary

Congratulations, you have finished the first chapter of this book. It is important that you have an understanding of the following terms because they will be reinforced throughout this book:

• Computer program
• Algorithm
• Design requirements
• User interface
• Bug
• Quality assurance (QA)
• Debugging
• Object-oriented programming (OOP)
• Object
• Property
• Method
• State of an object
• Integrated development environment (IDE)

What’s Next

The next 15 chapters provide the information you need to learn Swift and write iOS applications. Terms and concepts are introduced and reinforced over and over so you will begin to get more comfortable with them. Keep going and be patient with yourself.

Exercises

Answer the following questions:

• Why is it so important to spend time on your user requirements?
• What is the difference between design requirements and an algorithm?
• What is the difference between a method and a property?
• What is a bug?
• What is state?
• Write an algorithm for how a soda machine works from the time a coin is inserted until a soda is dispensed. Assume the price of a soda is 80 cents.
• Write the design requirements for an app that will run the soda machine.