How do you use NSOperationQueue?

NSOperationQueue *q = [[NSOperationQueue alloc] init]; /* Data to process */ NSData *data = [@”Hello, I’m a Block!” dataUsingEncoding: NSUTF8StringEncoding]; /* Push an expensive computation to the operation queue, and then * display the response to the user on the main thread.

What is the difference between GCD and NSOperationQueue?

Grand Central Dispatch is a low-level C API that interacts directly with Unix level of the system. NSOperation is an Objective-C API and that brings some overhead with it. Instances of NSOperation need to be allocated before they can be used and deallocated when they are no longer needed.

What is NSOperationQueue in Swift?

A queue that regulates the execution of operations.

What is DispatchQueue?

A DispatchQueue is an abstraction layer on top of the GCD queue that allows you to perform tasks asynchronously and concurrently in your application. Tasks are always executed in the order they’re added to the queue.

Why is DispatchGroup used in certain situations?

DispatchGroup allows for aggregate synchronization of work. It can be used to submit multiple different work items or blocks and track when they all complete, even though they might run on different queues. This blocks the current thread, but after the timeout specified, continues anyway.

What is NSThread?

The NSThread class supports semantics similar to those of NSOperation for monitoring the runtime condition of a thread. You can use these semantics to cancel the execution of a thread or determine if the thread is still executing or has finished its task.

What is Dispatchgroup?

A group of tasks that you monitor as a single unit.

What class will allow you to use one or more blocks concurrently?

BlockOperation class
The BlockOperation class is a concrete subclass of Operation that manages the concurrent execution of one or more blocks. You can use this object to execute several blocks at once without having to create separate operation objects for each.

What is semaphore in Swift?

A semaphore consist of a threads queue and a counter value (type Int). Threads queue is used by the semaphore to keep track on waiting threads in FIFO order (The first thread entered to the queue will be the first to get access to the shared resource once it is available).

What does DispatchQueue main Async do?

It blocks the queue and waits until the task is finished. Asynchronous function returns control on the current queue right after task has been sent to be performed on the different queue. It doesn’t wait until the task is finished.

How are operation and operationqueue used in iOS?

Concurrency means that your application executes multiple streams (or threads) of operations all at the same time. This way the user interface stays responsive as you’re performing your work. One way to perform operations concurrently in iOS is with the Operation and OperationQueue classes.

Is it easy to use nsoperation and dispatch queues?

The APIs like NSOperation and dispatch queues make it easy to use concurrency: Creating and managing threads are not easy tasks. This is why most of developers get scared when they hears the term concurrency and multi-threaded code.

Why are operation and operationqueue classes in Swift?

Operation and OperationQueue are higher level classes that have greatly simplified the process of dealing with multiple threads. As you can see, a process can contain multiple threads of execution, and each thread can perform multiple tasks one at a time.

How are operation and operationqueue built on top of GCD?

Operation and OperationQueue are built on top of GCD. As a very general rule, Apple recommends using the highest-level abstraction, then dropping down to lower levels when measurements show this is necessary. GCD is a lightweight way to represent units of work that are going to be executed concurrently.