Dependency inversion, SwiftUI previews

[kelvinlauKL (Kelvin Lau)]

I'm trying to find a way to minimize the compile time of SwiftUI view previews. I've heard that applying dependency inversion can help create a boundary and can prevent unnecessary compilation.

Ex:

If A -> C, any changes made in C would force A to recompile.

However, if you introduce a protocol B, such that:

• A -> B (A depends on B)
• B <- C (C adopts B)

Any changes to C will not recompile A, since A's contract with B is unchanged.

Based on that understanding, having SwiftUI views depend on abstract types (protocols) could reduce the compilation times of Xcode previews.

Is that understanding correct?

[mayoff (Rob Mayoff)]

Kevin Cathey talks about this in WWDC 2020 Session 10149: Structure your app for SwiftUI previews.

Point-Free has also been discussing this in their current series of episodes, “Designing Dependencies”, except that, due to a mild protocol allergy, they use a struct full of closures instead.