Initial support for caching values in-memory

Fix crash when multiple updates create publishers simultaneously

I've been working on a fix for a bug in Overamped, which causes the popover UI shown when tapping on an image in Google Images to be blank, if the link goes to an AMP page. This was a silly bug that never should've happened; knowing that Google can change their page structure at any time I should've been more cautious with my checks.

As a temporary quick fix I removed all custom handling of Google results, tested my changes in the simulator, and uploaded a new build to TestFlight.

After installing the TestFlight update on my phone I checked a search result that I knew recreated the problem, but it was still happening! I have other extensions installed so I disabled some, refreshed, and the bug was fixed!

I thought it would be very strange for the same – very specific – bug to appear in multiple extensions, so I did a little digging.

Fix deadlock when adding a new subscriber inside the closure of an update listener

Partial is now available in its own Swift package on GitHub. This post is still valid, but somewhat out of date.

Structs are incredibly useful in Swift, especially when representing static read-only data. However, the values of a struct often come from multiple sources, such as view controllers, network requests, and files on disk, which can make the creation of these structs cumbersome.

There are numerous methods to work around this, but each have their downsides. One of these methods is to change the struct to a class and update the properties to vars, but this removes the advantages of read-only structs. Another is to make a "builder" object, but the API of this object must be kept in-sync with the object is wraps.

Partial eliminates these problems by providing a type-safe API for building structs by utilising generics and KeyPaths. Although I learned of the concept of Partial through TypeScript – which [provides Partial as a built-in type][1] – the Swift implementation supports many more use cases.

• Much improved API - Split in to multiple targets in a single package