swift - Custom Controls for iOS are always offset -

i'm making few custom controls ios. each of these controls draws various layers in drawrect , every single 1 of layers seems offset reason. they're suppose centered in view. here's example of pie chart control:

override public func drawrect(rect: cgrect) {     super.drawrect(rect)      _valuelayers.foreach { (sublayer : calayer) -> () in         sublayer.removefromsuperlayer()     }     _valuelayers.removeall(keepcapacity: false)      let mindim = min(rect.size.width, rect.size.height)     let maxslicewidthscale : cgfloat = self.slicewidthscales.count > 0 ? min(self.slicewidthscales.sort(>).first!, cgfloat(1)) : kdefaultslicewidthscale     let maxslicewidth = maxslicewidthscale * mindim * 0.5     let center = rect.center()     let sum : float = self.values.reduce(0, combine: { $0.floatvalue + $1.floatvalue }).floatvalue     let maxradius = (mindim - maxslicewidth) * 0.5      var currentstartangle = self.startangle      var x = 0; x < self.values.count; x++ {         let ratio = self.values[x].floatvalue / sum         let angle = cgfloat(2.0 * m_pi * double(ratio))         let endangle = currentstartangle + angle         let slicewidthscale = self.slicewidthscales.count > x ? self.slicewidthscales[x] : kdefaultslicewidthscale         let slicewidth = slicewidthscale * mindim * 0.5          var radius = maxradius         switch self.slicealignment {         case .inner:             radius -= 0.5 * (maxslicewidth - slicewidth)         case .outer:             radius += 0.5 * (maxslicewidth - slicewidth)         case .center:             radius = maxradius         }          let arclayer = cashapelayer()         arclayer.frame = self.layer.frame         arclayer.fillcolor = uicolor.clearcolor().cgcolor         arclayer.path = uibezierpath(arccenter: center, radius: radius, startangle: currentstartangle, endangle: endangle, clockwise: self.clockwise).cgpath         arclayer.strokecolor = self.colors.count > x ? self.colors[x].cgcolor : kdefaultslicecolor.cgcolor         arclayer.linewidth = slicewidth          _valuelayers.append(arclayer)         self.layer.addsublayer(arclayer)          currentstartangle = endangle     }      if self.showshadow {         self.layer.maskstobounds = false         self.layer.shadowcolor = self.shadowcolor.cgcolor         self.layer.shadowopacity = self.shadowopacity         self.layer.shadowoffset = self.shadowoffset         self.layer.shadowradius = self.shadowradius     } } 

i cannot figure out why these controls offset in frame. doing wrong here?

the problem line of code:

arclayer.frame = self.layer.frame 

when layer's origin wasn't (0,0), sublayer being offset.