interview

Q1.What  is property?
Ans:Properties are used  to  access  the  instance  variables  from  outside  of  class.

Q2. What  is synthesized?
Ans:After  you  declare  the  property  in objective-c .  we  have to tell  the  compiler instantly  by  using  synthesize  directive. Actually  this  tells  to compiler  to generate  a  getter&setter  message.

3Q: How many bytes we can send to apple push notification server.
A:256bytes.

Q4. What is retaining?
Ans:It is reference count of the object

Q5. What is webservice?
Ans:Main  purpose is  to expose the data  in  form  of xml  format  ,by  using  this  we  can  getting  the  data  from  server.

Q6. What  is parsing?
Ans:To  access the data  in the  xml  element  is called  parsing.

Q7.Which class  we  can  use  for  passing  of xml  in  iphone?
Ans:By  “NSXML” Parser.

Q8.Which  type of  parse  we  have  use  in  iphone?
Ans:”SAX” parser.

Q9.Which  class are used to establish  connection  b/w application to webserver?
Ans:(a)NSURL
        (b)NSURL REQUEST
        (c)NSURL CONNECTION.

Q10.What  is difference between DOM&SAX?
Ans:(a)Dom is a documents based parser. When we will work with these parser all the data of xml is stored in RAM.In this parser  “memory consumption” is more.
(b)SAX  is  a  event  driven parser.When we will work with these parser,take only  reference  from  xml file  and  generate  the one event  for  every element.

Q11.After  parsing  if  you  want  to  get your data in  view  which  delegation  methods  are  did  you use?
Ans:(a)did  start  element      (b)did  end  element        (c)found  character.

Q12.How many  methods  are  used  in  NSURLConnection?
Ans:I  have 4 types methods
(a)Connection  did  receive  Response
(b)Connection  did  recevice  Datat
(c)Connection  fail  with error
(d)Connection  did  finish loading.

Q13.Tell  me  about  json-parser?
Ans:”JSON” Means  “Java script object notation”.
           It is a one  type  of  parser (or)test-based  and  lightweight  parser.

Q14.By  default application which  things  contain?
Ans:In ipone applications  by  default  having 3 things
1.mainIt is  entry  point of  application.
2.AppdelegateIt is  perform  the  basic application  &  functionality.
3.WindowIt  is  provide  uiinterface.

Q15.What is  uiviewcontroller?
Ans:   uiview controller  is base class for all the controller.

Q16. What is the navigation controller?
Ans: Navigation  controller contains the stack of controllers every navigation controller
         must be having root view controller by default these controllers contain 2 method
         (a) push view      (b) pop view
        By default navigation controller contain “table view”.

Q17. What is tab bar controller?
 Ans: Tab bar is used to common way to display the data on iphone.

Q18. What is the table view controller?
Ans: Table view controller contains the number of rows and columns visible in the
        application  and makes a cell editable or not as a response to key press

Q19. Which protocols are did used in table view
Ans: Table view contain 2 delegate protocols
      (a). Ui table view data source
              (b). Ui table view delegate.
         In ui view table view data source contain these methods
               (a). No of sections.
               (b). No of rows in sections.
               (c). Cell for row index path row.
        In ui table view delegate contain these methods
               (a). Did select row at index path row

Q20. By default table view which controller contain?
Ans: Detail view controller that is present is ui table view delegate

Q21.  What is the split view controller?
Ans: This control is used for ipad application and it contain proper controllers by default  split view controller contain root view controller  and detail view controller.

Q22.  What are data base are used in iphone?
Ans: (a). Sql lite (b). Plist c). Xml (d). core data

Q23. Tell me about the MVC architecture?
Ans: M-model, V-view, C-controller
         Main advantage of MVC architecture is to provide “reusability and security”
         by separating the layer by using MVC architecture.

         Model: it is a class model is interact with database.
         Controller: controller is used for by getting the data from model and controls the views.
         View: display the information in views.

Q24. What are frame works are used in iphone?
Ans:       (a). Ui kit framework
               (b). Map kit framework
               (c). ADI kit framework
               (d). Core data framework
               (e).core foundation framework

Q25. What is the instance methods?
Ans: Instance methods are essentially code routines that perform tasks so instances
        of clases we create methods to get and set the instance variables and to display
         the current values of these variables.

Declaration of instance method :
          - (void)click me: (id)sender;
          Void is return type which does not giving any thing here.
          Click me is method name.
          Id is data type which returns any type of object.

Q26. What is the class method?
Ans: Class methods work at the class level and are common to all instance of a
         class these methods are specific to the class overall as opposed to working
         on different instance data encapsulated in each class instance.
@interface class name :ns object
         {
          }
 +(class name *)new alloc:
 -(int)total open

Q27. What is data encapsulation?
Ans: Data is contained with in objects and is not accessible by any other than
         via methods defined on the class is called data encapsulation.
Q28. What is accessor  methods?
Ans: Accessor methods are methods belonging to a class that allow to get and set
         the values of instance valuables contained with in the class.

Q29. What is synthesized accessor methods?
Ans: Objective-c provides a mechanism that automates the creation of accessor
         methods that are called synthesized accessor methods that are
implemented through use of the @property and @synthesized.

Q30. How to access the encapsulated data in objective-c?
Ans:(a)Data encapsulation encourages the use of methods to +get and set the values of instance variables in a class.
 (b)But the developer to want to directly access an instance variable with out   having to go through an accessor method.        
(c) In objective-c syntax for an instance variable is as follow [class instance variable name]

Q31. What is dot notation?
Ans: Dot notation features introduced into version 2.0 of objective-c
         Dot notation involves accessing an instance variable by specifying
         a class “instance” followed by a “dot” followed in  turn by the name of instance variable or property to be accessed.

Q32. What is single inheritance in objective-c?
Ans: Objective-c subclass can only be derived from a single direct parent class this s concept is called as “single inheritance”.

Q33. Ns object is parent class or derived class?
Ans: NsObject is parent class and contains a number of instance variables and  instance methods.

Q34. How to call function in objective-c?
Ans:   [account display account info]
           Account-> object namey Subclassing the UIView class.
  Display account info-> method name

35Q: What is App Bundle?
A:When you build your iOS app, Xcode packages it as a bundle. A bundle is a directory in the file system that groups related resources together in one place. An iOS app bundle contains the app executable file and supporting resource files such as app icons, image files, and localized content.
From your code, access your app’s resource files using an NSBundle object:
             1. Use the mainBundle method of NSBundle to obtain your app’s main bundle object.
             2. Use the methods of the bundle object to obtain the location of the desired resource file.
            3. Open (or access) the file and use it.
The pathForResource:ofType: method is one of several NSBundle methods that you can use to retrieve the location of resource files in your bundle. The following example shows how to locate an image file called sun.png and create an image object. The first line gets the location of the file in the bundle. The second line creates the UIImage object using the data in the file at that location.

36Q: Whats fast enumeration?
A:Fast enumeration is a language feature that allows you to enumerate over the contents of a collection. (Your code will also run faster because the internal implementation reducesmessage send overhead and increases pipelining potential.)

37Q: Whats a struct?
A:A struct is a special C data type that encapsulates other pieces of data into a single cohesive unit. Like an object, but built into C. 

38Q: Whats the difference between  NSArray and  NSMutableArray?
A:NSArrayʼs contents can not be modified once itʼs been created whereas a NSMutableArray can be modified as needed, i.e items can be added/removed from it.

39 Q: Explain retain counts.
A:Retain counts are the way in which memory is managed in Objective-C. When you create an object, it has a retain count of 1. When you send an object a retain message, its retain count is incremented by 1. When you send an object a release message, its retain count is decremented by 1. When you send an object a autorelease message, its retain count is decremented by 1 at some stage in the future. If an objectʼs retain count is reduced to 0, it is deallocated.

40Q: Whats the difference between frame and bounds?
A:The frame of a view is the rectangle, expressed as a location (x,y) and size (width,height) relative to the superview it is contained within. The bounds of a view is the rectangle, expressed as a location (x,y) and size (width,height) relative to its own coordinate system (0,0).

41 Q: Is a delegate retained?
A:No, the delegate is never retained! Ever!

 42Q: Outline the class hierarchy for a UIButton until NSObject
A:UIButton inherits from UIControl, UIControl inherits from UIView, UIView inherits from UIResponder, UIResponder inherits from the root class NSObject

  43Q: What is dynamic?
A:You use the @dynamic keyword to tell the compiler that you will fulfill the API contract implied by a property either by providing method implementations directly or at runtime using other mechanisms such as dynamic loading of code or dynamic method resolution. It suppresses the warnings that the compiler would otherwise generate if it can’t find suitable implementations. You should use it only if you know that the methods will be available at runtime

44Q: If I call performSelector:withObject:afterDelay: – is the object retained?
A:Yes, the object is retained. It creates a timer that calls a selector on the current threads run loop. It may not be 100% precise time-wise as it attempts to dequeue the message fromthe run loop and perform the selector.

45Q: Can you explain what happens when you call autorelease on an object?
A:When you send an object a autorelease message, its retain count is decremented by 1 at some stage in the future. The object is added to an autorelease pool on the current thread. The main thread loop creates an autorelease pool at the beginning of the function, and release it at the end. This establishes a pool for the lifetime of the task. However, this also means that any autoreleased objects created during the lifetime of the task are not disposed of until the task completes. This may lead to the taskʼs memory footprint increasing unnecessarily. You can also consider creating pools with a narrower scope or use NSOperationQueue with itʼs own autorelease pool. (Also important – You only release or autorelease objects you own.)

46 Q: Whats the NSCoder class used for?
A:NSCoder is an abstractClass which represents a stream of data. They are used in Archiving and Unarchiving objects. NSCoder objects are usually used in a method that is being implemented so that the class conforms to the protocol. (which has something like encodeObject and decodeObject methods in them).

47 Q: Whats an NSOperationQueue and how/would you use it?
A:The NSOperationQueue class regulates the execution of a set of NSOperation objects. An operation queue is generally used to perform some asynchronous operations on a background thread so as not to block the main thread.

48Q: Explain the correct way to manage Outlets memory
A:Create them as properties in the header that are retained. In the viewDidUnload set the outlets to nil(i.e self.outlet = nil). Finally in dealloc make sure to release the outlet.
iOS Questions for  Expert level

49Q: Is the delegate for a CAAnimation retained?
A:Yes it is!! This is one of the rare exceptions to memory management rules.

50Q: What happens when the following code executes?
Ball *ball = [[[[Ball alloc] init] autorelease] autorelease];
A:It will crash because itʼs added twice to the autorelease pool and when it it dequeued the autorelease pool calls release more than once.


                                       iOS Questions  for Intermediate level


Q1. Where can you test Apple iPhone apps if you don’t have the device?
A. iOS Simulator can be used to test mobile applications. Xcode tool that comes along with iOS SDK includes Xcode IDE as well as the iOS Simulator. Xcode also includes all required tools and frameworks for building iOS apps.  However, it is strongly recommended to test the app on the real device before publishing it.

Q2. Does iOS support multitasking?
A. iOS 4 and above supports multi-tasking and allows apps to remain in the background until they are launched again or until they are terminated.  

Q3. Which JSON framework is supported by iOS?
A. SBJson framework is supported by iOS.  It is a JSON parser and generator for Objective-C. SBJson provides flexible APIs and additional control that makes JSON handling easier.

Q4. What are the tools required to develop iOS applications?
A. iOS development requires Intel-based Macintosh computer and iOS SDK.

Q5. Name the framework that is used to construct application’s user interface for iOS.
A. The UIKit framework is used to develop application’s user interface for iOS. UIKit framework provides event handling, drawing model, windows, views, and controls specifically designed for a touch screen interface.

Q6. Name the application thread from where UIKit classes should be used?
A. UIKit classes should be used only from an application’s main thread.  Note: The derived classes of UIResponder and the classes which manipulate application’s user interface should be used from application’s main thread. 

Q7. Which API is used to write test scripts that help in exercising the application's user interface elements?
A. UI Automation API is used to automate test procedures. Tests scripts are written in JavaScript to the UI Automation API.  This in turn simulates user interaction with the application and returns log information to the host computer.

Q8. Why an app on iOS device behaves differently when running in foreground than in background?
A. An application behaves differently when running in foreground than in background because of the limitation of resources on iOS devices.

Q9. How can an operating system improve battery life while running an app?
A. An app is notified whenever the operating system moves the apps between foreground and background.  The operating system improves battery life while it bounds what your app can do in the background. This also improves the user experience with foreground app.

Q10. Which framework delivers event to custom object when app is in foreground? 
A. The UIKit infrastructure takes care of delivering events to custom objects. As an app developer, you have to override methods in the appropriate objects to process those events.

Q11. When an app is said to be in not running state?
A. An app is said to be in 'not running' state when:
- it is not launched.
- it gets terminated by the system during running.

Q12. Assume that your app is running in the foreground but is currently not receiving events. In which sate it would be in?
A. An app will be in InActive state if it is running in the foreground but is currently not receiving events. An app stays in InActive state only briefly as it transitions to a different state.

Q13. Give example scenarios when an application goes into InActive state?
A. An app can get into InActive state when the user locks the screen or the system prompts the user to respond to some event e.g. SMS message, incoming call etc.

Q14. When an app is said to be in active state?
A. An app is said to be in active state when it is running in foreground and is receiving events.

Q15. Name the app sate which it reaches briefly on its way to being suspended.
A. An app enters background state briefly on its way to being suspended.

Q16. Assume that an app is not in foreground but is still executing code. In which state will it be in?
A. Background state.

Q17. An app is loaded into memory but is not executing any code. In which state will it be in?
A. An app is said to be in suspended state when it is still in memory but is not executing any code.

Q18. Assume that system is running low on memory. What can system do for suspended apps?
A. In case system is running low on memory, the system may purge suspended apps without notice.

Q19. How can you respond to state transitions on your app?
A. On state transitions can be responded to state changes in an appropriate way by calling corresponding methods on app's delegate object.
For example:
applicationDidBecomeActive method can be used to prepare to run as the foreground app.
applicationDidEnterBackground method can be used to execute some code when app is running in the background and may be suspended at any time.
applicationWillEnterForeground method can be used to execute some code when your app is moving out of the background
applicationWillTerminate method is called when your app is being terminated.

Q20. List down app's state transitions when it gets launched.
A. Before the launch of an app, it is said to be in not running state.
When an app is launched, it moves to the active or background state, after transitioning briefly through the inactive state.

Q21. Who calls the main function of you app during the app launch cycle?
A. During app launching, the system creates a main thread for the app and calls the app’s main function on that main thread. The Xcode project's default main function hands over control to the UIKit framework, which takes care of initializing the app before it is run.

Q22. What is the use of controller object UIApplication?
A. Controller object UIApplication is used without subclassing to manage the application event loop.
It coordinates other high-level app behaviors.
It works along with the app delegate object which contains app-level logic.

Q23. Which object is create by UIApplicationMain function at app launch time?
A. The app delegate object is created by UIApplicationMain function at app launch time. The app delegate object's main job is to handle state transitions within the app.

Q24. How is the app delegate is declared by Xcode project templates?
A. App delegate is declared as a subclass of UIResponder by Xcode project templates.

Q25. What happens if IApplication object does not handle an event?
A. In such case the event will be dispatched to your app delegate for processing.

Q26. Which app specific objects store the app's content?
A. Data model objects are app specific objects and store app’s content. Apps can also use document objects to manage some or all of their data model objects.

Q27. Are document objects required for an application? What does they offer?
A. Document objects are not required but are very useful in grouping data that belongs in a single file or file package.

Q28. Which object manage the presentation of app's content on the screen?
A. View controller objects takes care of the presentation of app's content on the screen. A view controller is used to manage a single view along with the collection of subviews. It makes its views visible by installing them in the app’s window.

Q29. Which is the super class of all view controller objects?
A. UIViewController class. The functionality for loading views, presenting them, rotating them in response to device rotations, and several other standard system behaviors are provided by UIViewController class.


Q30. What is the purpose of UIWindow object?
A. The presentation of one or more views on a screen is coordinated by UIWindow object.


Q31. How do you change the content of your app in order to change the views displayed in the corresponding window?
A. To change the content of your app, you use a view controller to change the views displayed in the corresponding window. Remember, window itself is never replaced.


Q32. Define view object.
A. Views along with controls are used to provide visual representation of the app content. View is an object that draws content in a designated rectangular area and it responds to events within that area.

Q33. You wish to define your custom view. Which class will be subclassed?
A. Custom views can be defined by subclassing UIView.

Q34. Apart from incorporating views and controls, what else an app can incorporate?
A. Apart from incorporating views and controls, an app can also incorporate Core Animation layers into its view and control hierarchies.

Q35. What are layer objects and what do they represent?
A. Layer objects are data objects which represent visual content. Layer objects are used by views to render their content. Custom layer objects can also be added to the interface to implement complex animations and other types of sophisticated visual effects.