Siesta

What is Siesta?

The Problem

Want your app to talk to a remote API? Welcome to your state nightmare!

You need to display response data whenever it arrives. Unless the requesting screen is no longer visible. Unless some other currently visible bit of UI happens to need the same data. Or is about to need it.

You should show a loading indicator (but watch out for race conditions that leave it stuck spinning forever), display user-friendly errors (but not redundantly — no modal alert dogpiles!), give users a retry mechanism … and hide all of that when a subsequent request succeeds.

Be sure to avoid redundant requests — and redundant response deserialization. Deserialization should be on a background thread, of course. Oh, and remember not to retain your ViewController / model / helper thingy by accident in your callback closures. Unless you’re supposed to.

Naturally you’ll want to rewrite all of this from scratch in a slightly different ad hoc way for every project you create.

What could possibly go wrong?

The Solution

Siesta ends this headache by providing a resource-centric alternative to the familiar request-centric approach.

Siesta provides an app-wide observable model of a RESTful resource’s state. This model answers three basic questions:

What is the latest data for this resource, if any?

Did the latest request result in an error?

Is there a request in progress?

…and broadcasts notifications whenever the answers to these questions change.

Siesta handles all the transitions and corner cases to deliver these answers wrapped up with a pretty bow on top, letting you focus on your logic and UI.

Overview