Home > Articles > Home & Office Computing > Entertainment/Gaming/Gadgets

Using Model-View-Controller Application Design for iPhone Development

Learn about the application design pattern known as Model-View-Controller and create a single iPhone application from start to finish.
This chapter is from the book

You've come a long way in the past few hours—you've provisioned a developer profile for your phone, learned the basics of the Objective-C language, explored Cocoa Touch, and gotten a feel for Xcode and Interface Builder. Although you've already used a few prebuilt projects, you have yet to build one from scratch. That's about to change!

In this hour, you will learn about the application design pattern known as Model-View-Controller and create a single application from start to finish.

Understanding the Model-View-Controller Paradigm

When you start programming, you'll quickly come to the conclusion that there is more than one "correct" way to do just about everything. Part of the joy of programming is that it is a creative process that allows you to be as clever as your imagination allows. This doesn't mean, however, that adding structure to the development process is a bad idea. Having a defined and documented structure means that other developers will be able to work with your code, projects large and small will be easy to navigate, and you'll be able to reuse your best work in multiple applications.

The application design approach that you'll be using on the iPhone is known as Model-View-Controller (MVC), and will guide you in creating clean, efficient applications.

Making Spaghetti

Before we get into MVC, let's first talk about the development practice that we want to avoid, and why. When creating an application that interacts with a user, several things must be taken into account. First, the user interface. You must present something that the user interacts with: buttons, fields, and so on. Second, handling and reacting to the user input. Finally, the application must store the information necessary to correctly react to the user—frequently in the form of a database.

One approach to incorporating all of these pieces is to combine them into a single class. The code that displays the interface is mixed with the code that implements the logic and the code that handles data. This can be a very straightforward development methodology, but it limits the developer in several ways:

  • When code is mixed together, it is difficult for multiple developers to work together because there is no clear division between any of the functional units.
  • The interface, application logic, and data are unlikely to be reusable in other applications because the combination of the three is too specific to the current project to be useful elsewhere.
  • The application is difficult to extend. Adding features requires working around existing code. The developer must work around the existing code to include new features, even if they are unrelated.

In short, mixing code, logic, and data leads to a mess! This is known as "spaghetti code" and is the exact opposite of what we want for our iPhone applications. Model-View-Controller to the rescue!

Structured Application Design with MVC

MVC defines a clean separation between the critical components of our apps. As implied by the name, MVC defines three parts of an application:

  • A model provides the underlying data and methods that provide information to the rest of the application. The model does not define how the application will look or how it will act.
  • One or more views make up the user interface. A view consists of the different onscreen widgets (buttons, fields, switches, and so forth) that a user can interact with.
  • A controller is typically paired with a view. The controller is responsible for receiving the user's input and acting accordingly. Controllers may access and update a view using information from the model and update the model using the results of user interactions in the view. In short, it bridges the MVC components.

The logical isolation created between the functional parts of an application, illustrated in Figure 6.1, means the code becomes more easily maintainable, reusable, and extendable—the exact opposite of spaghetti code.

Figure 6.1

Figure 6.1 MVC design isolates the functional components of an app.

Unfortunately, MVC comes as an afterthought in many application development environments. A frequent question that I am asked when suggesting MVC design is, "How do I do that?" This isn't indicative of a misunderstanding of what MVC is or how it works, but a lack of a clear means of implementing it.

In the Apple Development Suite, MVC design is natural. As you create new projects and start coding, you'll be guided into using MVC design patterns automatically. It actually becomes more difficult to program poorly than it does to build a well-structured app.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020