ios - How to draw at the centre of a subview -

i want draw arrow @ center of subview created

    {let arrowview = arrowview()     arrowview.frame = cgrect(x: selectbutton.frame.minx, y: selectbutton.frame.maxy, width: selectbutton.frame.width, height: processbutton.frame.miny - selectbutton.frame.maxy)     arrowview.backgroundcolor = uicolor.white     arrowview.viewwithtag(100)     view.addsubview(arrowview)     } //these codes in view controller  

to draw arrow in subview use

    let arrowpath = uibezierpath.bezierpathwitharrowfrompoint(startpoint: startpoint, endpoint: endpoint, tailwidth: 4, headwidth: 8, headlength: 6) // error occurs here  override func draw(_ rect: cgrect) {     let fillcolor = uicolor.white     fillcolor.setfill()      arrowpath.linewidth = 1.0     let strokecolor = uicolor.blue     strokecolor.setstroke()      arrowpath.stroke()     arrowpath.fill()  //these codes in subclass of uiview 

since want draw arrow @ center of subview, define startpoint , endpoint

    private var startpoint: cgpoint {     return cgpoint(x: bounds.midx, y: bounds.miny) } private var endpoint: cgpoint {     return cgpoint(x: bounds.midx, y: bounds.maxy) }  //try find point @ centre of subview 

however, code not compile , error says:

cannot use instance member 'startpoint' within property initializer; property initializers run before 'self' available

edit: know how bounds of subview created code. try "bounds" variable above error.

arrowpath.center = cgpoint(x:arrowview.frame.size.width/2, y: arrowview.frame.size.height/2)  arrowview.addsubview(arrowpath)