How to print() to Xcode console in SwiftUI?

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You can easily add a print statement anywhere in a function builder by simply storing its return value in a wildcard, effectively ignoring it:

let _ = print("hi!")

No setup or other verbosity needed!

Why does this work while a regular print() doesn’t?

The way SwiftUI’s @ViewBuilder (and result builders in general) is that they consume any values in a closure that aren’t used otherwise (e.g. if you just have 42 on its own line). The print function returns Void (nothing), which the builder would have to build into a view, so it fails. By instead assigning it to a variable (in this case _, basically a variable that you can never access), the Void is never offered to the view builder in the first place.

You could argue the builder should simply accept and ignore Void values, but the idea is that your builder closures should not have side effects (I’d remove print statements after finishing debugging too)—you should not rely on these closures being called at certain times.

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