Yet another "Cannot use instance member printGreeting within property initializer"

I found an example of some code which achieves my goal. However, I am getting the above error upon compiling. Searching on-line, I found solutions when the member in question was a variable, but not when it is a function. Here are excerpts:

class ViewController : UIViewController {

...
func printGreeting (modifier: UnsafePointer<CChar>) {
  print( ...)
}

var callbacks = SomeCLibCallbacks (
    funcToCall: { (modifier)in                             
    printGreeting(modifier: modifier)          //<- error here
    )
}

}