In which thread are all controller operations performed?

Not all controller operations are performed on the same thread.

• Most UI operations (interface updates, touch event handling) are executed on the main thread.
• Operations that can block the main thread (e.g., sending network requests, processing large volumes of data, disk operations) should be performed on background threads.

Typical scenarios for using background threads:

1. Grand Central Dispatch (GCD):

   DispatchQueue.global(qos: .userInitiated).async {
       // Long operations, such as network requests
       // After completing the background task, update the UI on the main thread
       DispatchQueue.main.async {
           // UI update
       }
   }
   

2. Operation Queues:

   let queue = OperationQueue()
   queue.addOperation {
       // Long operations
       OperationQueue.main.addOperation {
           // UI update
       }
   }
   

3. async/await (in Swift Concurrency):

   Task.detached(priority: .userInitiated) {
       // Long operations
       await MainActor.run {
           // UI update
       }
   }
   

Executing all operations on the main thread will block the interface (freeze the app), which will negatively affect the user experience.