interview
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.
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.main→It
is entry point of application.
2.Appdelegate→It
is perform the basic application &
functionality.
3.Window→It
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.
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.
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 reduces
message 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:NSArrayΚΌs contents can not be
modified once itΚΌs 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 objectΚΌs
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 from
the 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
taskΚΌs memory footprint increasing unnecessarily.
You can also consider creating pools with a narrower scope or use
NSOperationQueue with itΚΌs 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 itΚΌs
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.
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.
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.
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.
A. The UIKit framework is used to develop application’s user 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.
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.
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.
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.
A. An app is notified whenever the operating system
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.