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

This chapter is from the book

Preparing a View to Perform Layer Animation

The first thing you want to do when you create a Core Animation based project is to make sure the root layer of your view is layer backed. Let's walk through creating a Core Animation-based project and set up the root layer on OS X.

Create the Xcode Project

To create our application, follow these steps:

  1. In Xcode, press shift-cmd-n.jpg and select Cocoa Application in the Project Templates dialog.
  2. Name the project CA Basics and click Save.
  3. Expand the Frameworks group, Control-click the Linked Frameworks subgroup, and select Add > Existing Frameworks.
  4. In the resulting dialog, navigate to /System/Library/Frameworks and select QuartzCore.framework. Click Add twice, as prompted.
  5. Control-click the Classes group and select Add > New File.
  6. In the New File template dialog, select Objective-C class under the Cocoa group and click Next.
  7. Name the file AppDelegate.m and make sure Also Create "AppDelegate.h" is checked; click Finish.
  8. Select AppDelegate.h to open the file in the code editor and add the following code:
        @interface AppDelegate : NSObject {
           IBOutlet NSWindow *window;
  9. Select AppDelegate.m to open the file in the code editor and add the following code:
       @implementation AppDelegate
    - (void)awakeFromNib;
        [[window contentView] setWantsLayer:YES];
  10. Under the Resources group in your project, double-click MainMenu.xib to open the XIB in Interface Builder.
  11. From the Library palette in Interface Builder, drag an NSObject object into MainMenu.xib and rename it to AppDelegate.
  12. Make sure the AppDelegate object is selected. In the object inspector, click the Identity tab and change the Class field to AppDelegate.
  13. In the MainMenu.xib, Control-click on File's Owner and drag the connection to the AppDelegate object. Select delegate in ensuing context menu.
  14. In the MainMenu.xib, Control-click on AppDelegate and drag the connection to the Window object. Select window in the ensuing context menu.
  15. Save the xib file and return to Xcode.

The project is now set up. In the preceding steps, we created an application delegate that we use to provide control to our layer, window, and view.

Add the Animation Layer to the Root Layer

To add a layer that we will be animating, do the following:

  1. Open AppDelegate.h and add a CALayer instance variable:
        @interface AppDelegate : NSObject
        IBOutlet NSWindow *window;
        CALayer *layer;
  2. Open AppDelegate.m and add the layer initialization code in -awakeFromNib:
    @implementation AppDelegate
    - (void)awakeFromNib;
        [[window contentView] setWantsLayer:YES];
        layer = [CALayer layer];
        [layer setBounds:CGRectMake(0.0, 0.0, 100.0, 100.0)];
        // Center the animation layer
        [layer setPosition:CGPointMake([[window contentView]
                           [[window contentView]
        CGColorRef color = CGColorCreateGenericRGB(0.4, 0.3, 0.2, 1);
        [layer setBackgroundColor:color];
        [layer setOpacity:0.75];
        [layer setBorderWidth:5.0f];
        [[[window contentView] layer] addSublayer:layer];

Layer Allocation Considerations

Another consideration of which you should be aware when you set up your layers is that even though you have an instance variable (ivar) of your CALayer, it is not retained unless you explicitly retain it. In the world of memory management in Objective-C, the rule of thumb is that you retain only that which you need to retain. You should not retain objects you don't need to hold onto, and you should retain objects that you do need. It sounds simple, but in practice it tends to be more elusive. In our code in the previous steps, you see we allocate our layer by using the convenience initializer layer = [CALayer layer];. This allocates an auto-released CALayer object. When the layer object goes out of scope in the –awakeFromNib, it will be auto-released unless it is retained. In our case, we are adding it to the contentView layer sublayers array, which is retaining the layer for us. If, however, we wanted to wait until later to actually add the layer that we initialized in –awakeFromNib to the sublayers array, we need to allocate the layer by using layer = [[CALayer alloc] init]. Then we need to release the layer in the dealloc method with a call to [layer release];.

The first time you go to use the CALayer method called –removeFromSuperlayer, you will find that if you try to add the layer to the sublayer array again, it will crash your application. This is because the layer will be released in the call to –removeFromSuperlayer. You must retain the layer yourself if you want to remove it from its superlayer but keep it around in memory.

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