Is it possible to determine the name of the caller of a function from within that function?

Using Swift
1

Hello,
The other day I was designing a class that was a singleton and wanted to have a warning printed if anyone called its init() except for that class itself. I then realised that I could simply mark the init() as private, which was very useful. Problem solved.

However, I still was curious about how I could have solved the problem if the solution wasn't available and that lead me to wonder if it's possible to get the name of the caller of a function. e.g.

func caller() {
	print("I am the caller")
	print("function: \(#function)")
	callee()
}

func callee() {
	print("I am the callee")
	print("function: \(#function)")

	print("Caller: \(someWayToGetTheNameOfTheCaller())")

	let origin = Thread.callStackSymbols
	print(origin[0])
}

caller()

I found from a cursory Google that Thread.callStackSymbols() exists, but that provides an array of Strings which contain the memory address of the caller.
e.g.

0 ??? 0x0000000100728904 0x0 + 4302473476

Is there a way to get the actual name of the calling function?
This is just out of curiosity. I don't require this functionality, but I find it interesting.
Thanks.

2

You can have a parameter in a function with a default value of #function. However I don't find this very safe if wanting functions to be called from specific callers, that's what access is for (like you have found).

func caller() {
    callee()
}

func callee(_ caller: String = #function) {
    print(caller) // callee
}
1 Like
3

Thanks!