Concurrency

Users always want more. With a background URLSession, we can give them more by extending downloads and uploads beyond the app's lifespan. Here, we look at building a solution to take advantage of a background session to download adorable cat photos 😸.

DateFormatters are expensive to build, so we cache them. DateFormatters are useful, so we share that cache. DateFormatters are mutable, so we end up with hard-to-reproduce bugs. Here, we look at how to cache and share DateFormatters without the bugs that come from them being shared mutable state.

Operations have a reputation for being chunky, especially compared to GCD. However, once you get to know operations, you realise that they are the OOP approach to concurrency in iOS. Here, we look at how to use operations to build a networking layer by encapsulating multiple steps into one unit.

In iOS, we can use background-transfers to extend the life of our downloads and uploads beyond the app's lifespan, offering our users a better experience by using a background URLSession. Here, we look at how to build that better experience.

Every time a user has to wait for a network request to complete before they can get on with their task, we risk losing them. With pausable downloads, we can ensure that even a cancelled download isn't wasted. Here, we look at how to resume a cancelled download to minimise wait times.

We are often told that no matter where you end up, you shouldn't forget where you came from. Usually, this saying is applied to people, but it can also apply to code. Here, we look at how to capture the originating thread when kicking off a background task so that we can return to it later.

Operations are a powerful way to move work off the main thread. But just because work is undertaken on a background thread doesn't mean we don't care about it. Here, we look at how to coalesce duplicated work.

No one wants networking code scattered everywhere. Here, we look at how to utilise NSOperation to encapsulate each networking request within its own cancellable unit of work.

Sometimes, when you need to know, you need to poll. Here, we look at building a polling mechanism using `NSOperation`.

Moving work onto a background thread can be hard. Here, we look at how to keep it simple.