Home > Articles > Home & Office Computing > Mac OS X

This chapter is from the book

In Interface Builder

In the outline view under Resources, you will find a nib file called MainMenu.nib. Double-click on it to open the nib in Interface Builder. Lots of windows will appear, so this is a good time to hide your other applications. In the Interface Builder menu, you will find Hide Others.

Interface Builder allows you to create and edit user interface objects (like windows and buttons) and save those objects into a file. You can also create instances of your custom classes and make connections between those instances and the standard user interface objects. When users interact with the user interface objects, the connections you have made between them and your custom classes will cause your code to be executed.

The Standard Palettes

The palette window (Figure 2.7) is where you will find user interface widgets that can be dragged into your interface. For example, if you want a button, you can drag it from the palette window. Notice the row of buttons at the top of the palette window. As you click the buttons, the various palettes will appear. In Chapter 27, you will learn to create your own palettes.

02fig07.jpgFigure 2.7 Palette

The Blank Window

The blank window (Figure 2.8) represents an instance of the NSWindow class that is inside your nib file.

02fig08.jpgFigure 2.8 Blank

As you drop objects from the palettes onto the window, they will be added to the nib file. After you have created instances of these objects and edited their attributes, saving the nib file is like "freeze-drying" the objects into the file. When the application is run, the nib file will be read and the objects will be revived. The cool kids say, "The objects are archived into the nib file by Interface Builder and unarchived when the application is run."

Lay Out the Interface

I am going to walk you through it, but keep in mind that your goal is to create a user interface that looks like Figure 2.9.

02fig09.jpgFigure 2.9 Completed

Drag a button from the palette window (as shown in Figure 2.10) and drop it onto the blank window.

02fig10.jpgFigure 2.10 Dragging a Button

Double-click on the button to change its title to Seed random number generator with time.

Drag another button out, and relabel it Generate random number. Drag out the text field that says System Font Text (as shown in Figure 2.11) and drop it on the window

02fig11.jpgFigure 2.11 Dragging a Text Field

Make the window smaller.

The text field should be as wide as possible. Drag the left and right sides of the text field toward the sides of the window. Notice that blue lines appear when you are close to the edge of the window. These guides are intended to help you conform to Apple's GUI guidelines (Figure 2.12).

02fig12.jpgFigure 2.12 Resize Text Field

To make the text field center its contents, you will need to use the Info Panel (also known as the "Inspector"). Select the text field, and choose Show Info from the Tools menu. Click on the center justify button (Figure 2.13).

02fig13.jpgFigure 2.13 Center Justify Text Field

The Doc Window

In your nib file, some objects (like buttons) are visible, and others (like your custom controller objects) are invisible. The icons that represent the invisible objects appear in the doc window (Figure 2.14).

02fig14.jpgFigure 2.14 The Doc Window

In the doc window (the one entitled MainMenu.nib), you will see icons representing the main menu and the window. First Responder is a fictional object, but it is a very useful fiction. It will be fully explained in Chapter 18. File's Owner in this nib is the NSApplication object for your application. The NSApplication object takes events from the event queue and forwards them to the appropriate window. We will discuss File's Owner in depth in Chapter 9.

Create a Class

The doc window also has a simple class browser that you can use to create a skeleton of your custom class. Click on the Classes tab and select NSObject (Figure 2.15). In the Classes menu, choose Subclass NSObject. Rename the new class Foo. Interface Builder now knows that you intend to create a subclass of NSObject called Foo. NSObject is the root class for the entire Objective-C class hierarchy. That is, all objects in the framework are descendants of NSObject.

02fig15.jpgFigure 2.15 Foo Is a Subclass of NSObject

Class names, by convention, are capitalized.

Next, you will add instance variables and methods to your class. Instance variables that are pointers to other objects are called outlets. Methods that can be triggered by user interface objects are called actions. If you select the Foo class and bring up the inspector (use the Show Info menu item to activate the inspector), you will see that your class doesn't have any outlets or actions yet (Figure 2.16).

02fig16.jpgFigure 2.16 View Outlets and Actions

To add an outlet, select the Outlets tab and click Add. Rename the new outlet textField. You can set the type of the pointer in a pop-up. Here textField will be a pointer to an NSTextField object. Set its type using the pop-up as shown in Figure 2.17.

02fig17.jpgFigure 2.17 Create an Outlet

To add an action, select the Actions tab and click Add. Rename the new action seed. (When you press Enter, it will add a colon to the end of the action name. Thus seed: is the actual name of the method that will be created.) Add a second action, and name it generate: (Figure 2.18).

02fig18.jpgFigure 2.18 Create Two Actions

By convention, the names of methods and instance variables start with lowercase letters. If the name would be multiple words in English, each new word is capitalized—for example, favoriteColor.

Now you will create the files for the class Foo. In Objective-C, every class is defined by two files: a header file and an implementation file. The header file, also known as the interface file, declares the instance variables and methods your class will have. The implementation file actually defines what those methods do.

Under the Classes menu, choose Create files for Foo. . . (Figure 2.19).

02fig19.jpgFigure 2.19 Create

A save panel will appear. The default location (your project directory) is perfect. Save Foo.h (the header file) and Foo.m (the implementation file) there. Note that the files are being added to your RandomApp project (Figure 2.20).

02fig20.jpgFigure 2.20 Choose a Location for the Files

Create an Instance

Next, you will create an instance of the class Foo in your nib file. Select Foo in the class browser and choose Instantiate Foo from the Classes menu (Figure 2.21).

02fig21.jpgFigure 2.21 Create an Instance of Foo

Interface Builder will take you back to the Instances tab, where you will see a symbol representing your instance of Foo (Figure 2.22).

02fig22.jpgFigure 2.22 An Instance of Foo

Make Connections

A lot of object-oriented programming has to do with which objects need to know about which other objects. Now you are going to introduce some objects to each other. Cocoa programmers would say, "We are now going to set the outlets of our objects." To introduce one object to another, you will control-drag from the object that needs to know to the object it needs to know about. The object diagram in Figure 2.23 shows which objects need to be connected in your example.

02fig23.gifFigure 2.23 Object

You will set Foo's textField instance variable to point to the NSTextField object on the window that currently says System Font Text. Control-drag from the symbol that represents your instance of Foo to the text field. The inspector panel will then appear. Choose textField in the view on the left, and click Connect. You should see a dot appear next to textField (Figure 2.24).

02fig24.jpgFigure 2.24 Set the textField Outlet

This step is all about pointers: You have just set the pointer textField in your Foo object to point to the text field.

Now you will set the Seed button's target outlet to point to your instance of Foo. Furthermore, you want the button to trigger Foo's seed: method. Control-drag from the button to your instance of Foo. Choose the Target/Action tab in the inspector and select seed:. Click the Connect button to complete the connection (or double-click the word seed:). You should see a dot appear next to seed: (Figure 2.25).

02fig25.jpgFigure 2.25 Set the Target and Action of the Seed Button

Similarly, you will set the Generate button's target instance variable to point to your instance of Foo and set its action to the generate: method. Control-drag from the button to Foo. Choose generate: in the Target/Action view. Double-click on the action name (generate:) to complete the connection. Note the appearance of the dot (Figure 2.26).

02fig26.jpgFigure 2.26 Set the Target and Action of the Generate Button

You are done with Interface Builder, so save the file and hide the application. Click on the Xcode icon in the dock to bring Xcode to the front.

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.


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.


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.


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.


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


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


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.


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.


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