使用 Swift 的 AudioToolbox 访问 OS X 主音量

Question

Is there a solution to setting the system's master volume from within my Swift app?

I read a lot about AudioToolbox and read some source examples in Objective-C. For example, I found this: Setting Mac OS X Volume Programatically after 10.6

But I can't get it working in Swift.

I am missing some example code in https://developer.apple.com/library/mac/documentation/AudioToolbox/Reference/AudioHardwareServicesReference/index.html#//apple_ref/c/func/AudioHardwareServiceGetPropertyData

Answer 1

(Code updated for Swift 4 and later, the Swift 2 and 3 versions can be found in the edit history.)

This is what I got from translating the answers to Change OS X system volume programmatically and Setting Mac OS X volume programmatically after 10.6 (Snow Leopard) to Swift (error checking omitted for brevity):

Required framework:

import AudioToolbox

Get default output device:

var defaultOutputDeviceID = AudioDeviceID(0)
var defaultOutputDeviceIDSize = UInt32(MemoryLayout.size(ofValue: defaultOutputDeviceID))

var getDefaultOutputDevicePropertyAddress = AudioObjectPropertyAddress(
    mSelector: kAudioHardwarePropertyDefaultOutputDevice,
    mScope: kAudioObjectPropertyScopeGlobal,
    mElement: AudioObjectPropertyElement(kAudioObjectPropertyElementMaster))

let status1 = AudioObjectGetPropertyData(
    AudioObjectID(kAudioObjectSystemObject),
    &getDefaultOutputDevicePropertyAddress,
    0,
    nil,
    &defaultOutputDeviceIDSize,
    &defaultOutputDeviceID)

Set volume:

var volume = Float32(0.50) // 0.0 ... 1.0
var volumeSize = UInt32(MemoryLayout.size(ofValue: volume))

var volumePropertyAddress = AudioObjectPropertyAddress(
    mSelector: kAudioHardwareServiceDeviceProperty_VirtualMasterVolume,
    mScope: kAudioDevicePropertyScopeOutput,
    mElement: kAudioObjectPropertyElementMaster)

let status2 = AudioObjectSetPropertyData(
    defaultOutputDeviceID,
    &volumePropertyAddress,
    0,
    nil,
    volumeSize,
    &volume)

Finally, for the sake of completeness, get the volume:

var volume = Float32(0.0)
var volumeSize = UInt32(MemoryLayout.size(ofValue: volume))

var volumePropertyAddress = AudioObjectPropertyAddress(
    mSelector: kAudioHardwareServiceDeviceProperty_VirtualMasterVolume,
    mScope: kAudioDevicePropertyScopeOutput,
    mElement: kAudioObjectPropertyElementMaster)

let status3 = AudioObjectGetPropertyData(
    defaultOutputDeviceID,
    &volumePropertyAddress,
    0,
    nil,
    &volumeSize,
    &volume)

print(volume)

Error checking has been omitted for brevity. Of course one should check the status return values for success or failure in a real application.

Credits go to Set OS X volume in OS X 10.11 using Swift without using the deprecated AudioHardwareServiceSetPropertyData API for using AudioObjectSetPropertyData() instead of the deprecated AudioHardwareServiceSetPropertyData() .

As noamtm mentions in the comments, this works also for getting and setting the left-right balance, by passing

mSelector: kAudioHardwareServiceDeviceProperty_VirtualMasterBalance

to AudioObjectPropertyAddress() .