THE BEST ENHANCEMENT: Extend #if targetEnvironment() for Previews, Widgets, and More.

FB.txt

We have this in SwiftUI:

    #if targetEnvironment(simulator)

Yet it’s rarely useful, because SwiftUI code that’s being used in a preview is being run in a simulator.

The distinction that developers need is whether the code is being used in a preview or in the Simulator app.

The root of the problem is that View data is kept in two separate locations:

    Previews: ~/Library/Developer/Xcode/UserData/Previews/Simulator Devices/
    Simulator app: ~/Library/Developer/CoreSimulator/Devices/

When working in a dynamic environment like SwiftUI, you will often want to experiment using model data that’s not kept in a shared location like a group container or AppStorage. You may also want to adjust model data to see what edge cases look like. Something like this would let you do this without affecting the code paths you want to use in a real app:

    #if targetEnvironment(preview)

A similar issue, not necessarily related to SwiftUI, is that the code you want to execute in the context of an app is often very different than that of an extension (e.g. primarily widgets, but can be other types such as a photo editing extension).

These extension contexts often come with limited resources (both processing time and memory footprint). Something like this would let the developer deal with these disparate situations:

    #if targetEnvironment(widget)

An example here would be using a lightweight model based on UserDefaults or a group container for the Widget case, and a more expressive model with a database backing store, networking, etc. when compiling for the app.

This has been a longstanding need for developers. Here is a three year old post on Stack Overflow:

https://stackoverflow.com/questions/58759987/how-do-you-check-if-swiftui-is-in-preview-mode

SO BEST ENHANCEMENT PLS