How Grand Central Dispatch works?

GCD is built on top of threads. Under the hood, it manages a shared thread pool. With GCD, you add blocks of code or work items to dispatch queues and GCD decides which thread to execute them on. As you structure your code, you’ll find code blocks that can run simultaneously and some that should not.

What is Libdispatch?

Grand Central Dispatch (GCD or libdispatch), is a technology developed by Apple Inc. to optimize application support for systems with multi-core processors and other symmetric multiprocessing systems. It is an implementation of task parallelism based on the thread pool pattern.

What is Grand Central Dispatch iOS?

Grand Central Dispatch is used in iOS to introduce concurrency and parallelism in the iOS applications, so that multiple heavy tasks are performed in the background, resulting in the smooth experience of the application usage, as the main thread is unaffected by the heavy background tasks.

What is DispatchGroup?

DispatchGroup allows for aggregate synchronization of work. You can use them to submit multiple different work items and track when they all complete, even though they might run on different queues. This behavior can be helpful when progress can’t be made until all of the specified tasks are complete.

What went wrong with Libdispatch?

The libdispatch kind of made it too easy, developers started dispatching left and right without really thinking anymore about what was actually going on in their software and hardware, it pushed developers away from careful design.

What is concurrent in Swift?

The concurrency model in Swift is built on top of threads, but you don’t interact with them directly. An asynchronous function in Swift can give up the thread that it’s running on, which lets another asynchronous function run on that thread while the first function is blocked.

What is Dispatchsemaphore?

A semaphore can be used to emulate a dispatch group. You start the sempahore at 0, start all the tasks – tracking how many you have started and wait on the semaphore that number of times. Each task must signal the semaphore when it completes.

What is NSOperationQueue?

A queue that regulates the execution of operations.