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Chapter 4,An "Invalid timestamps for HID response delay" thing i met

Hi guys,i met a strange thing when following topic “Debugging views and state changes” at page 107,which is in Chapter 4: Testing & Debugging

With page 107,first i add this line of code “let _ = Self._printChanges()” after the" var body: some View" ,declaring the body property for the view,and then a error appears after i build failed, showing ‘_printChanges()’ is only available in Mac Catalyst 15.0 or newer.

Next I change “Development Info” to “iOS 15” in “General” tab at this project’s Target page,after that I got a successful build.

But in the test,every time i press a button,there is a “Invalid timestamos for HID response delay” showing between every two “DisplayView:display changed.”

Is this normal? why i got a “printChanges()’ is only available in Mac Catalyst 15.0 or newer” at the beginning?

Thank you!!