Demonstration of app threads in swift

SimpleThreads.swift

// Application threads
// Background
func BG(_ block: @escaping () -> Void) {
    DispatchQueue.global(qos: .default).async(execute: block)
}

// Main
func UI(_ block: @escaping () -> Void) {
    DispatchQueue.main.async(execute: block)
}

// Example
BG { [unowned, weak self] in
    // load data on background thread
    self.viewModel.loadData() { [weak self] data in
      UI {
        // Updating UI
        self?.updateData(data)
      }
  }
}