Is this system object pointer code at all possible in Swift?

Question

I was pointed to this objc snippet from WWDC 14, but I work on a Swift project.

CMIOObjectPropertyAddress prop = { kCMIOHardwarePropertyAllowScreenCaptureDevices, kCMIOObjectPropertyScopeGlobal, kCMIOObjectPropertyElementMaster }; UInt32 allow = 1; CMIOObjectSetPropertyData(kCMIOObjectSystemObject, &prop, 0, NULL, sizeof(allow), &allow);

I then tried rewriting to Swift:

var prop : CMIOObjectPropertyAddress { kCMIOHardwarePropertyAllowScreenCaptureDevices kCMIOObjectPropertyScopeGlobal kCMIOObjectPropertyElementMaster } var allow:UInt32 = 1 CMIOObjectSetPropertyData(kCMIOObjectSystemObject, &prop, 0, nil, sizeof(UInt32), &allow)

But it doesn't even validate. I don't know how to translate the CMIOObjectPropertyAddress struct. Xcode says

/Users/mortenjust/Dropbox/hack/learning/screenrec/screenrec/deleteme.swift:32:61: Cannot assign to a get-only property 'prop'

Oh, forgot to add, I got it working by bridging an objective-c class that does only the stuff above. I want to avoid this, as bridging headers make Xcode autocompletion incredibly slow. — Morten J
– Morten J, Commented May 6, 2015 at 2:33

matt · Accepted Answer · 2015-05-06 04:07:08Z

A C struct translates as a Swift struct. Use the implicit memberwise initializer:

 var prop = CMIOObjectPropertyAddress( mSelector: UInt32(kCMIOHardwarePropertyAllowScreenCaptureDevices), mScope: UInt32(kCMIOObjectPropertyScopeGlobal), mElement: UInt32(kCMIOObjectPropertyElementMaster))

The cool part is when you type CMIOObjectPropertyAddress(, code completion gives you the rest.

Morten J · Accepted Answer · 2015-05-06 04:09:16Z

You're right, just got it running right this second. Turns out I also had to correct for some of the types. Here's the complete translation:

 var prop = CMIOObjectPropertyAddress( mSelector: CMIOObjectPropertySelector(kCMIOHardwarePropertyAllowScreenCaptureDevices), mScope: CMIOObjectPropertyScope(kCMIOObjectPropertyScopeGlobal), mElement: CMIOObjectPropertyElement(kCMIOObjectPropertyElementMaster)) var allow : UInt32 = 1 var dataSize : UInt32 = 4 var zero : UInt32 = 0 CMIOObjectSetPropertyData(CMIOObjectID(kCMIOObjectSystemObject), &prop, zero, nil, dataSize, &allow) var session = AVCaptureSession() session.sessionPreset = AVCaptureSessionPresetHigh var devices = AVCaptureDevice.devices() for device in AVCaptureDevice.devices() { println(device) }

Thanks for reporting back. Could be useful to others! (Swift numerics are maddening, aren't they?)

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