Multitasking support is available from which version?
iOS 4.0
What is a structure?
A struct is a special data type C which encapsulates other data elements into a cohesive unit. As an object, but built in C.
Which iPhone OS?
iPhone OS running on the iPhone and iPod touch.
Hardware devices are managed by the iPhone OS and provides the necessary implementing native applications on the phone technologies.
The system comes with a variety of system applications such as Mail, Safari, Phone, which provide standard services to users.
What is @interface?
- It’s a keyword used to declare the Class.
What is @implementation?
- It’s a keyword used to define the Class.
Garbage collector in iPhone?
- iOS 5.0 has got the ARC ( Automated reference counting
). Objective C does not have a garbage collector rather it uses the
reference counting algorithm to manage the memory. This was the developers task
until Apple launched iOS 5.0. Again if you are targeting iOS 4.0 or earlier ,
ARC is no more a choice for you .
What is delegate?
- Delegate is an object that handles the events happening on an
object. To do that delegate has to follow a protocol specifying the task it is
going to handle .
What is @synthesize?
- We use @synthesize to generate getters and setters
automatically from compiler. We declare properties and then generate
getter and setter method by using @synthesize.
What are the features of iOS 5.0 ?
- https://developer.apple.com/technologies/ios5/
What is nonatomic ?
- nonatomic and atomic are related to
multithreading environment .
- If a property has an attribute as “nonatomic” that means
multiple threads can modify that property concurrently.
- If the attribute is “atomic”, the threads would be given
access atomically.
- So “Atomic” is thread safe while “nonatomic” is
thread unsafe.
- Atomic drastically hampers the performance so until and unless
not needed you should never go for atomic attribute. ‘nonatomic ’ will do in
most of the cases.
What are the delegate methods of
MKMapView ?
- Check the MKMapViewDelegate in the Documentation. If you don’t
have Xcode with you then search on Google.
What are the important delegate methods of
NSXML parser?
-DidStartElement
-FoundCharecters
-DidEndElement
-FoundError
What is @dynamic and any place where it is
used ?
- It tells compiler that getter and setter are not implemented
by the class but by some other class .
- May be super class or child class .
Example – Core Data
- The Managed object
classes have properties defined by using @dynamic.
What is @property?
- It is a keyword used to declare a property.
What is data source?
- The datasource is an object that implements the required
datasource protocol that is needed to create a complex control.
Ex UITableView is a view that needs a datasource object to which
will help building the table. Often it’s the controller that is displaying the
table view. The protocol that dataSource object ( mostly controller it self)
has to implement is “UITableViewDataSource” .
What is model view controller?
- MVC is a Design pattern .
Model stands for the database object which will
manage all the database transaction .
- View stands for the UI i.e. the UI visible to the user. User
will be interacting with the view.
- Controller is an object who handles the view events and also
render the database changes to the UI. In short , it bridges the interaction
between Modal and View.
what is @ protocol?
- @protocol is a keyword used to define a protocol. A protocol
is a set of method declarations defining specific purpose. It only lists out
the methods prototype , the actual implantation would be provided by the class
that implements / follows the protocol.
what is id?
- id is a generic reference type. The variable declared using id
data-type can hold any object. Most of the methods that returns an object has
‘id’ as return type. Ex – init.
Explain memory management?
- Most of the object oriented languages have the Garbage
Collector . All the objects are allocated on the heap memory. The
Garbage Collector is a thread that runs periodically to check all the objects,
which are no more being referenced from the program. Garbage collector then
de-allocates all these unreferenced objects on the Heap. In this environment
programmer does not need to worry about de-allocating the objects explicitly.
In Objective – C we don’t have garbage collector. ( Note: Its
available from iOS 5.0 only). So in this environment we have to explicitly take
care of allocation and deallocation of all the objects in our
program. And to manage this Objective C uses ‘reference counting’
algorithm as the memory management algorithm.
Reference Counting: In this algorithm every object keeps track
of it owners ( I,e reference variables from the program ) . No of owners is
represented by the property retainCount declared in NSObject. If this
retainCount goes to ‘0’ the object gets deallocated
automatically. We never call dealloc method on any object
explicitly.
what is retain and release?
- retain and release are two method defined in NSObject . - -
- These methods are related to Memory Mangement .
- retain method when called increases the retainCount by 1.
- release method when called decreases the retainCount by 1
what is dealloc?
- dealloc method is called on an object to actually deallocate
the memory for that object. ( We should never call dealloc directly )
- In reference counting environment when retainCount of an
object reaches to ‘0’, the dealloc method is called on that object
automatically to delete the memory space of the object .
- If the object is having some reference type variable holding
other objects, then we should call release method on every variable in dealloc.
- If you override then [super dealloc] should be the last line
in this method.
What is Autorelease pool?
- Autorelease pool is like a container that holds the
autoreleased objects .
- This pool is drained with every run-loop of the Application
- When the pool gets drained, autorelease pool sends a release
message to all the objects it was holding.
What is Foundation Framework? Can you explain
some classes from that?
- Foundation is one of the important frameworks in COCOA Touch.
- It contains the classes like NSArray , NSString ,
NSObject etc .
What is the difference between NSArray and
NSMutableArray?
* NSArray
- is a static
array
- Once created you can
not modify the array
- Ex you can not add or
remove the object in NSArray.
* NSMutableArray
- is a dynamic array
- You can add or remove
the object dynamically.
Write a delegate method of the table view?
- (void)tableView:( UITableView*)tableView
didSelectRowAtIndexPath:(NSIndexPath*)indexPath
What are the delegate methods of
NSURLConection?
- didReceiveResponse:
- didReceiveData:
- didFinishLoadingData:
- didFailWithError:
What is cocoa ?
- COCOA is a collection of frameworks used to write Applications
for MAC OS X.
Singleton classes
- A singleton class is such a class from which no more that one
instance can be created. So there will always be single instance created
throughout the program.
Ex UIApplication.
