How to Call a Private macOS CoreFoundation Function from Swift

Question

I'm looking for a way to use a private Apple API from within Swift code (namely, _CFPreferencesCopyApplicationMap, which allows you to look up the paths used for user defaults for any given application).

See this answer for the motivation & the Objective-C solution. I was able to do this in Objective-C with the line:

extern CFDictionaryRef _CFPreferencesCopyApplicationMap(CFStringRef userName, CFStringRef hostName);

I haven't been able to figure out how to do the same in Swift. I know it's possible to dynamically access ObjC objects at runtime using NSClassFromString or NSSelectorFromString, but as far as I can tell these can't be used with global C functions. NSInvocation likewise seems out.

The way you did it is correct. Use Objective C. – matt Jul 13 '20 at 03:43 — matt, Jul 13 '20 at 03:43

score 2 · Accepted Answer · answered Aug 21 '20 at 03:58

It turns out that this is possible using @_silgen_name:

@_silgen_name("_CFPreferencesCopyApplicationMap")
func _CFPreferencesCopyApplicationMap(_: CFString!, _: CFString!) -> CFDictionary!

// Then, call as:
let applicationMap = _CFPreferencesCopyApplicationMap(kCFPreferencesCurrentUser, kCFPreferencesAnyHost) as? [String: [URL]]

How to Call a Private macOS CoreFoundation Function from Swift

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