Hello World iOS4 Application using Xcode 3.2.3

Apple just announced general availability for iOS4 so I thought I would document how to write a simple HelloWorld application for the iPhone 4.

How-To: Write Hello World using Interface Build and Xcode Templates for Apple’s iOS4

1. Start Xcode 3.2.3 (available for download as part of the iPhone 4 SDK http://developer.apple.com/iphone/index.action)
2. Select View-based Application
   
3. Open View Controller .xib in Interface Builder (located in Resource folder)
   • View controllers don’t have a visual presentation
   • Mange views, but do *not* display anything of their ow
   • Each View Controller has an instance variable called “view” which is set to some type of UIView.
4. File’s Owner
   • Proxy that represents the object that loaded (and consequently) owns the .xib
5. View
   • You can see the View in the View Controller is owned by the File’s Owner
6. Drag a Label from the Library to the design surface
7. Drag a Button from the Library to the design surface
    
8. Close Interface Builder and switch back to Interface Builder
9. Open the header file
10. Add an instance variable to your class (called an interface in Objective-C)
11. Define the property using the instance variable as a backing field
     
12. Switch to the implementation file for the View Controller
    • The @synthesize directive automatically generates the setters and getters for us, so all we have to implement for this class is the dealloc method.
    • Accessors will only be generated if they don't already exist, so feel free to specify @synthesize for a property, then implement your custom getter or setter if you want. The compiler will fill in whichever method is missing
      
      
13. Release the UILabel in the dealloc method.
     
14. Switch back to Interface Builder
15. Switch to the Inspector Tool Window
16. Click on File’s Owner 
17. Drag the myLabel Outlet to the View UILabel.
    
18. Close Interface Builder and switch back to Xcode
19. Add a new Action in the Controller’s header
     
20. Switch back to Interface Builder
21. Control Click on the Button and drag Touch Up Inside event to the myButtonPushed Action in File’s Owner
    
22. Implement a UISlider
     
23. Run the application in the Simulator
     

Once you have the app working in the Simulator, you can deploy to your device.