How do I lock the white balance in AVfoundation for swift? -

i'm trying lock iphone facing camera's white balance current state having trouble point of converting objective-c code swift. code in objective-c:

[device setwhitebalancemode:avcapturewhitebalancemodelocked]; 

this thought code in swift should like:

capturedevice.setwhitebalancemode(avcapturewhitebalancemode.locked) 

and xcode tells me this:

'avcapturedevice' not have member named 'setwhitebalancemode' 

        if capturedevice.lockforconfiguration(nil) {             var gains: avcapturewhitebalancegains = avcapturewhitebalancegainscurrent             capturedevice.setwhitebalancemodelockedwithdevicewhitebalancegains(gains, completionhandler:nil);             capturedevice.unlockforconfiguration()         }