Tasks vs Threads

Low-level process management never changes.

Today, we’re going to look at the power of the old-school Thread APIs, and demonstrate how much it has in common with Tasks, the modern building block of Swift Concurrency.

Back when I was a fresh-faced junior, we had a really smart engineer on my team, Jeff. I asked him to explain iOS concurrency to my graduate cohort, and he explained there were 3 levels of abstraction:

1. Operation & OperationQueue at the top-level, with advanced functionality.

2. GCD as your bread-and-butter for basic concurrency workloads.

3. Thread for low-level precise management of actual threads.

My impostor-syndrome-riddled brain filled in the blanks: I knew any time I heard “low-level” it meant “for geniuses”.

The Thread API was out-of-bounds, for the really smart engineers.

Until today.

It wasn’t until I started writing this piece that I realised, a lot of the APIs available in Thread are copied by the Task in Swift Concurrency. By comparing them, we can understand both at a deeper level.

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