Can you explain the differences between using threads and GCD queues in asynchronous work?

Threads — are low-level concurrency mechanisms where each thread is a separate execution flow with its own stack and context. Managing threads requires explicit creation, synchronization, and resource management, which can be complex and error-prone (e.g., data races).

GCD (Grand Central Dispatch) — is a high-level API for managing asynchronous tasks through queues. GCD abstracts thread management, allowing tasks to be placed in queues that the system executes on a pool of threads optimally. This simplifies parallelism and improves performance without manual thread management.

Main differences:

• Threads are explicit units of execution requiring manual management.
• GCD is a task queue where tasks are executed on system-managed threads.
• GCD simplifies asynchronous programming, reducing synchronization errors.

Example of using GCD for an asynchronous task:

DispatchQueue.global(qos: .background).async {
    // Long operation
    let result = heavyComputation()
    DispatchQueue.main.async {
        // UI update
        updateUI(with: result)
    }
}