Difference between DispatchQueue types in swift

Question

As I understand there are 3 types of DispatchQueue in swift:

• Main (serial) (Main Thread)
• Global (Concurrent) (Background

Answer 1

As I understand:

Queue is not Thread

Main and global queue may work in same thread

Dispatched: means put task in queue

If Global queue dispatched in Main queue as sync , the dispatched task will work on same thread of Main queue and dispatched task added to Global queue , And this task will freezing the thread

If Global queue dispatched in Main queue as async , the dispatched task will work on other thread of Main queue and dispatched task added to Global queue , And this task will not freezing the thread

If Main queue dispatched in Main queue as async , the dispatched task will work on same thread of Main queue

If Main queue dispatched in Main queue as sync will make exception because make deadlock

Dispatch.sync: put task in queue and wait it until finish

Dispatch.async: put task in queue and not wait it until finish (The task may work in same thread or in another thread)

• If task dispatched on Global queue and this accord from Main thread then the task will added to Global queue , and new thread will be create and the task will start working immediately in the new thread

• If task dispatched on Main queue and this accord from Main thread then the task will added to Main queue , and will not work immediately until older tasks in queue finish working (because Main queue is sequential )