hot objective c (iphone) Job Interview Questions And Answers

What happens when you send autorelease or retain message to autorelease pool?

NSAutoreleasePool  *autoRelease =[ [[ NSAutoreleasePool alloc] init] autorelease]; or

NSAutoreleasePool  *autoRelease =[ [[ NSAutoreleasePool alloc] init] retain];

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 11:45:42

What is property?

Properties are used  to  access  the  instance  variables  from  outside  of  class.

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 09:55:43

What is synthesized?

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.

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 09:56:32

What is retaining?

It is reference count of the object

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 09:58:40

What is webservice?

Main  purpose is  to expose the data  in  form  of  xml  format  and  json format ,by  using  this  we  can  getting  the  data  from  server.Third party data fetch.Json format most of use.

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 10:01:30

What is parsing?

To  access the data  in the  xml or json element  is called  parsing.

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 10:03:11

Which class we can use for passing of xml in iphone?

By  “NSXML” Parser

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 10:05:37

Which type of parse we have use in iphone?

”SAX” parser.

objective c iphone interview question for experience and fresher

objective c (iphone)   2013-04-24 10:06:24

Which class are used to establish connection b/w application to webserver?

• NSURL
• NSURL REQUEST
• NSURL CONNECTION

objective c (iphone)   2013-04-24 10:07:54

What is difference between DOM & SAX?

• 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.
• 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.

objective c (iphone)   2013-04-24 10:10:26

After parsing if you want to get your data in view which delegation methods are did you use?

• did start element
• did end elemen
• found character.

objective c (iphone)   2013-04-24 10:15:06

Difference between categories and extensions?

Class extensions are similar to categories. The main difference is that with an extension, the compiler will expect you to implement the methods within your main @implementation, whereas with a category you have a separate @implementation block. So you should pretty much only use an extension at the top of your main .m file (the only place you should care about ivars, incidentally) — it’s meant to be just that, an extension.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 10:54:42

Can we use two tableview controllers on one view controller?

Yes, we can use two tableviews on the same view controllers and you can differentiate between two by assigning them tags…or you can also check them by comparing their memory addresses.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 10:59:46

What is keyword atomic in Objective C?

When you place keyword atomic with a property, it means at one time only one thread can access it.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 11:01:10

Difference between shallow copy and deep copy?

Shallow copy is also known as address copy. In this process you only copy address not actual data while in deep copy you copy data.

Suppose there are two objects A and B. A is pointing to a different array while B is pointing to different array. Now what I will do is following to do shallow copy.
Char *A = {‘a’,’b’,’c’};
Char *B = {‘x’,’y’,’z’};
B = A;
Now B is pointing is at same location where A pointer is pointing.Both A and B in this case sharing same data. if change is made both will get altered value of data.Advantage is that coping process is very fast and is independent of size of array.

while in deep copy data is also copied. This process is slow but Both A and B have their own copies and changes made to any copy, other will copy will not be affected.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 10:53:21

What is difference between implementing a category and inheritance? 


What is advantage of categories?

You can add method to existing class even to that class whose source is not available to you. You can extend functionality of a class without subclassing. You can split implementation in multiple classes. While in Inheritance you subclass from parent class and extend its functionality.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 10:54:13

Difference between protocol in objective c and interfaces in java?

Protocol is also way to relate classes that are not related in inheritance hierarchy. Protocols and interfaces both are used to achieve multiple inheritance.

There is minor difference between these two. In Objective-C, protocols also implement NSObject protocol to access all the mehthods in NSObject

@protocol WebProtocol <NSObject>

@end

If I don’t implement NSObject explicitly, I will not be able to access NSObject methods like retain, release etc. when I access through WebProtocol instance.

While in Java you don’t need to implement Object interface explicitly. It is implicitly implemented.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 10:55:26

What are KVO and KVC?

KVO: Normally instance variables are accessed through properties or accessors but KVC gives another way to access variables in form of strings. In this way your class acts like a dictionary and your property name for example “age” becomes key and value that property holds becomes value for that key. For example, you have employee class with name property.

You access property like

NSString age = e.age;

setting property value.

e.age = @”16″;

Now how KVC works is like this

[e valueForKey:@"age"];

[e setValue:@"34" forKey:@"age"];

KVO : The mechanism through which objects are notified when there is change in any of property is called KVO.

For example, person object is interested in getting notification when accountBalance property is changed in BankAccount object.To achieve this, Person Object must register as an observer of the BankAccount’s accountBalance property by sending an addObserver:forKeyPath:options:context: message.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 10:58:31


What are mutable and immutable types in Objective C?


Mutable means you can change its contents later but when you mark any object immutable, it means once they are initialized, their values cannot be changed. For example, NSArray, NSString values cannot be changed after initialized.

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 11:01:37

Swap the two variable values without taking third variable?


int x=10;
int y=5;
x=x+y;
NSLog(@”x==> %d”,x);

y=x-y;
NSLog(@”Y Value==> %d”,y);

x=x-y;
NSLog(@”x Value==> %d”,x);

objective c iphone 1 year experiences interview question.

objective c (iphone)   2013-05-07 11:04:22