IOS Interview Questions

1. What are the important characteristics of IOS?

Ans: Below are a few important characteristics of IOS:

• The display is paramount regardless of its size
• Device orientation can change
• Apps respond to gestures, not clicks
• People interact with one app at a time
• Onscreen users help is minimal 
• Safari’s on IOS provides the web interface.

2. Mention the differences between IOS and Android devices?

Ans: 

3. Mention the differences between IOS and Windows devices?

Ans: The below table will explain the major differences between IOS and Windows

4. Which JSON framework is supported by IOS (iPhone OS)?

Ans:

• SBJSON framework is mainly supported by IOS devices. This framework is available in the form of a JSON parser and generator for object-oriented programming language. JSON framework is a superset of the programming language called C and offers object-oriented features and capabilities.
• SBJSON APIs is a flexible application programming interface and offers additional controlling features to handle JSON easier way.

5. Name the framework that is used to construct the application user interfaces for IOS?

Ans: 

UIkit framework: this type of framework is mainly used to develop user interfaces. The following are the few features of using the UIKIT framework;

• Event handling
• Drawing model
• Windows
• Views
• Controls.

UIkit. The framework offers the complex infrastructures required to construct and manage IOS application devices.

• UIkit’s windows and view architecture used to manage user interfaces
• Event handling infrastructures needed to respond to the user inputs.

6. How can you respond to state transitions on your app?

Ans: There are 4 methods used to respond to state transitions such as;

• ApplicationDidBecomeActive () method: this method is used to run the foregroup apps
• ApplicationDidEnterBackground () method: this method is used to execute the codes
• ApplicationWillEnterForeground () method: this method is used to execute the codes which are running background
• ApplicationWillTerminate () method: this method is called to terminate the apps.

7. What are the features added in IOS 9?

Ans: You can see the following features added in IOS 9:

• Intelligent search
• Siri voice recognition app
• Deeper search capabilities
• Performance improvements
• Wireless car play support
• Optional iCloud drive app

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8. What is the difference between RETAIN and ASSIGN?

Ans: ASSIGN is used to create references from one object to another, the below program will explain this;

If (_variable ! = object)

{

  [_variable release];

  _variable = nil;

  _variable = object;

}

RETAIN used to create the differences between one object and another;

If (_variable! = object)

{

  [_variable release];

  Variable = nil;

  _variable = [object retain];
 
}

9. Which are the ways of achieving concurrency in IOS?

Ans: Below are the three ways to achieve concurrency;

• Threads
• Dispatch queues
• Operation queues.

10. Explain the different types of IOS application states?

Ans: The different application states of IOS included are;

Not running state: this state is used when the app has not been launched yet, or that was terminated by the system.

Inactive: this state is used when the application is running in the foreground and not receiving any events.

Active state: when applications are running in the foreground and receiving events by that time this state is used.

Background state: this state is used to run the application in the background and execute the codes.

Suspended state: this state is used to terminate the program.

11. Which is the application thread from where UIKIT classes should be used?

Ans: A UIKIT class uses the application thread from the application’s main thread.

12. When would you say that an app is not in a running state?

Ans: Below are the two ways which explain this;

• When it is not yet launched
• during the running time, when the app is terminated by the system.

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13. What are layer objects in IOS?

Ans: The layer objects are nothing but data objects which represent the visual features, views and render the contents. These layers are custom layers that are added to the interfaces to execute any complex animations.

14. What is Sprite kit and Scene kit?

15. What is SWIFT?

Ans: A SWIFT is one of the programming languages used in the development of IOS applications. SWIFT language adopts safe programming patterns and offers many modern features to make programming easier to implement, flexible, and more fun to write.