ios - Unable to update the model layer upon CoreAnimation completion -

i have following function. it's purpose animate ui elements out of the screen's bounds.

func animateelementsout(elements: anyobject...) {      var moveoutanimation : cakeyframeanimation = cakeyframeanimation(keypath: "transform");     moveoutanimation.delegate = self;      var key1 : nsvalue = nsvalue(catransform3d: catransform3didentity);     var key2 : nsvalue = nsvalue(catransform3d: catransform3dmaketranslation(-300, 0, 0));      var values : nsarray = [key1, key2];      var delayamount = 0.0;      moveoutanimation.values = values;      moveoutanimation.calculationmode = kcaanimationlinear;     moveoutanimation.timingfunction = camediatimingfunction(name: kcamediatimingfunctioneasein);     moveoutanimation.duration = 0.5;      moveoutanimation.additive = true;      element : anyobject in elements {         delayamount += 0.1;         moveoutanimation.removedoncompletion = true;         moveoutanimation.begintime = cacurrentmediatime() + delayamount;         element.layer?.addanimation(moveoutanimation, forkey: "move object along x axis");          // here lies problem         element.layer?.position = cgpointmake(-330.0, 0.0);       }   } 

now here's xcode complaining about, when try update property directly on model layer, elements not reset initial positions.

it's giving me these weird recommendations:

why can't set position of layer?

thanks in advance!

element.layer?.position optional chain , may result in nil. can't assign nil. first make sure can layer , set position.

if let layer = element.layer {    layer.position = cgpointmake(-330.0, 0.0); }