Interview Questions: Dispatch Queues (Serial Queues, Concurrent Queues)

1. Name few C based API in iOS ?
Ans: SQLITE, GCD

2. What is Concurrency(in iOS) in short?
Ans: It help us to write efficient, fast execution of our app and for more responsive. But at the same time, if we misusing, it will ruin our app with our any mercy. For that reason we should think twice to write any concurrency code.

3. What are most commonly used APIs to implement concurrency Code?
Ans: NSOperation and Dispatch Queues.

4. Name few concepts that needed to write concurrent code?
Ans: Blocks (we call ‘closures' in Swift Programming Language)

5. What are Queues?
Ans: Its a DS(Data Structure) which manages the objects in an order - FIFO(First in First Out)

6. In which form you submit your task to the queue?
Ans: In the form of a block.

7. What is an Dispatch Queues?
Ans: Its one of the ways to perform tasks in asynchronously and concurrently in our applications.

8. What is meant by a Block in iOS?
Ans: Its just a block of Code.

9. Do we have any other queues under the Dispatch Queues?
Ans: Yes.

10. What are Queues under Dispatch Queues?
Ans: Serial Queues, Concurrent Queues.

11. Do we have any thread running by default? If so, what is that?
Ans: Yes, its main Tread.

12. Do we have any Serial Queue running by default?
Ans: Yes, ‘main thread’ is the default Serial Queue.

13. Can we create our own Serial Queue and Concurrent Queue?
Ans: Yes.

14. What is Serial Queue?
Ans: Serial Queue can only execute one task at a time. But at a time we execute multiple tasks from two different serial Queues separately , which means at anytime one serial queue execute only one task.

15. when is the good  situation to use serial Queues?
Ans: Its really for managing shared resource. And its guaranteeing serialized access to the shared resource and prevent race conditions. we can use, when we have a situation to execute tasks in predicable order. 


Will post on Concurrent Queues soon..... 

If you liked it or need any interview Question on specific topic, please leave a comment here..(You can reach me @iosdeveloper.ipa@gmail.com for any assistance on iOS & Unix).

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