[swift-users] Exclamation mark's in swift parameter listings?

Ethin Probst harlydavidsen at gmail.com
Mon Jan 9 18:23:00 CST 2017

Hello all,
I was wondering what an exclamation mark in a swift parameter listing
means. For instance, I used Elements Oxidizer Live to translate some
C# code into Swift. Reviewing it, I found the following (among
private static __extern func scriptRegister(_ module: System.IntPtr!,
What I'm wondering is what does the '!' in that list of parameters
mean? I also saw it when writing another program:
    func MainForm_Load(_ sender: System.Object!, _ e: System.EventArgs!) {
// ...
I don't recall the swift book teaching you what that means, so could
someone tell me what those mean?
Ethin D. Probst

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