I am familiar with IBInspectable and IBDesignable, and have, for example, put my own Smalltalk and Postscript implementations in IB that way. Not the same thin

I am familiar with IBInspectable and IBDesignable, and have, for example, put my own Smalltalk and Postscript implementations in IB that way. Not the same thing. At all. Not even close. Palettes were final-packaged components that were at the same level as pre-built ones. IBDesignable is a way for adding some interactivity to the views you are creating for an app while you're building said app. Like SwiftUI Previews. And it works about as well, that is not really at all. With IBDesignable, Xcode was continually trying to build the entire dependency tree, meaning for example the entire Postscript interpreter. And failing >50% of the time, which then kills your view. I hear the same happens with SwiftUI previews once your project gets bigger. It certainly happened to me almost immediately when I was trying it out. Again, they're not even close.