UIScrollView is one of the most important and useful controls in iOS. It is the basis for the very popular UITableView and is a great way to present content larger than a single screen.

You must set the contentSize property to the size of the scrollable content. This specifies the size of the scrollable area

1.Explain some features included in iOS 9 

​Answer:

Siri and Intelligent Search:

Siri is a helpful assistant you can talk to, but it is also the nice technology that powers search on your iOS devices (iPhone ,iPad).

1.What is the use of store kit framework?
​
Answer:

The Store Kit framework provides classes that allow an app to request payment from a user for additional functionality or content that your application provides.

The NSURLConnection class provides convenience class methods to load URL requests both asynchronously using a callback block and synchronously.

You can use NSURLConnection class in two ways.

1.Synchronous
​2.Asynchronous

1.What is iBeacon or iBeacons?
Answer:

An iBeacon is a low cost, low-energy bluetooth device which emits a signal broadcasting a unique ID within short distances.
​
​iBeacon and Beacon are almost used interchangeably.

​Define @property, @synthesize, @implementation, @interface in iOS.

Answer:
@property:
@property is a policy to define getter- and setter-methods, or as we call them accessors in Objective-C. 
Suppose you are declaring a NSInteger variable in Objective c like

1.What are the benefits of Application sandboxing ?
Answer:
The sandbox creates and builds a exclusive environment of data and information for each and every app.

​The sanbox can reduce the potential harms that can be caused by a potential hackers to an iOS device but it can't prevent the attack from happening

1. Define Visibility in Objective C?
Answer:-
Visibility :
The Objective C has variable by default @protected. But methods are not used with access specifier they are public by default. To hide any method from out side . Declare and Implement it in .m file using category .

1.What is the NSCoder class used for?
Answer:

 NSCoder is an abstractClass which represents a stream of data. They are used in Archiving and Un-archiving objects. NSCoder objects are usually used in a method that is being implemented so that the class conforms to the protocol.

1.  What is the iPhone?
Answer: 
In this post we will discuss some basic questions and answers before jumping into coding for Application development.

​The iPhone is an integrated cellular telephone and media player developed and marketed by Apple.

1.What are sensors in iPhone?
Answer: 

The proximity sensor immediately turns off the display when the iPhone is lifted to ear.

​With this sensor the power is saved and accidental dialling is prevented.

1.What is IBOutlet in iOS?
Answer:

IBOutlet is a macro defined to denote variables and methods that can be referred to in Interface Builder.

IBOutlets are used to hook up your interface made in Interface Builder with your controller

1.Difference between method and selector?
Answer:
​
Selector:
A Selector is the name of a method.

Method :
 A method is a combination of a selector and an implementation.

1.If I call performSelector:
withObject:
afterDelay: – is the object retained? 
 Answer:
Yes the object is retained. It creates a timer that calls a selector on the current thread's 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.

1.Outline the class hierarchy for a UIButton until NSObject. 

Answer:
UIButton inherits from UIControl, UIControl inherits from UIView, UIView inherits from UIResponder, UIResponder inherits from the root class NSObject.

1.What is the difference between the "copy" & "mutableCopy"?

Answer:-
copy returns an immutable (can't be modified) copy of the array.

mutableCopy returns a mutable (can be modified) copy of the array.

1.What is Core Data?
Answer:

Core Data is a framework that manages an object graph.

It is used to store data from your iPhone application into a Sqlite file which is present in the document directory of your application. 
Read:
​How to Explain  iOS Application LifeCycle ?

1.What are the ways to store data locally on iPhone ?
Answer:

Ans. We can store data locally in iOS devices through:

          1.  Plist.
          2.  NSUserDefaults.
          3.  SQLite.
          4.  CoreData.

1.What you mean by auto layout in Objective C?
Answer :

 Auto Layout is a new way to define dynamic GUIs. Before we had autoresizing masks, that described how a subview will resize or move when it’s superview is resized.

With Auto Layout you can do the same and also a lot more complicated GUIs quite easily.

1.What's the difference between UITabBarController and UINavigationController?
Answer:

UITabBarController:
​
Applications use tab bar controllers to manage multiple distinct interfaces, each of which consists of any number of custom views and view controllers.

1.Difference Between View and ViewController in iPhone?
Answer:
​
View Controller:

ViewController class is used to control the UIView instance (object) and the view which are present in the UIView (buttons,labels,table).

1.What is the difference Between APPKit and UIKit?
Answer:
AppKit

AppKit is included in the OS X SDK only.It provides all the classes and controls you need for creating Mac applications.Most of these classes share a common naming prefix starts with NS and classes you will be working with include NSWindow, NSButton, NSTableView.

1.What’s JSON? 
Answer:

JSON is known as JavaScript Object Notation.It is a text-based, lightweight and easy way for storing and exchanging data.

It’s commonly used for representing structural data and data interchange in client-server applications, serving as an alternative to XML.

1.Difference b/w #define and #pragma and  #import?
Answer:

#define
There are different ways to create   constants in Objective-C, but the easiest way is to use #define statements.#define however is a preprocessor that replaces all instance with it  even before compilation starts.

I am looking forward to deliver the best iOS Interview questions  to help the developers.

This is one of my best samples to target for beginners.
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What you just need is a strong passion to build your own app and send your valuable feedback,so that I can gather more stuffs.
Read:
Most Important iPhone interview Questions and Answers