ios - Reason why UIView doesn't animate -

i doing on ios in swift. trying animate uiview updating frame. created custom subclass of uitextfield. code have follows.

import foundation import uikit  enum textfieldstate {    case active    case inactiveblank    case inactivetext } /**    use class create text field in new workout vc  */ class textfield: uitextfield {    // mark: properties    /// color accent elements    private let standardcolor: uicolor = color().blue    /// color error elements    private let errorcolor: uicolor = color().red    /// font inactive state    private let inactivefont: uifont = fonts.regular().sixteen    /// font active state    private let activefont: uifont = fonts.bold().thirtysix    /// font hint active state    private let activehintfont: uifont = fonts.regular().sixteen    /// font hint in inactive state    private let inactivehintfont: uifont = fonts.regular().twelve    /// placeholder , hint text field    let placeholdertext: string     /// type of field    let type: textfieldtype    /// bottom line text field    var bottomline: uiview { return self.createbottomline() }    /// placeholder field    var placeholderlabel: uilabel { return self.createplaceholderlabel()     }    /// rect editing , text bounds    private var textbounds: rect {       return rect(x: 0, y: 31, w: self.frame.w, h: 96)    }    /// variable text of text field     // mark: initializers  /// default initalizer  init<a: textfieldoptions>(frame: cgrect, options: a) {     // set placeholder text value     self.placeholdertext = options.placeholdertext     // set type of text field     self.type = options.type     // call super initalizer     super.init(frame: frame)     // update settings based on type     self.styletype()     // set delgate text field     self.delegate = self     // set background color     self.backgroundcolor = color().white     // set font text field     self.font = self.activefont     // layout views     self.layoutviews()   }    /// required apple never use   required init?(coder adecoder: nscoder) {       fatalerror("this class doesn't support nscoding")    }    // mark: functions private func layoutviews() {    // add placeholder text text field   self.addsubview(self.placeholderlabel)   // add bottom line text field   self.addsubview(self.bottomline)  }  private func styletype() {    if self.type == .all {       self.returnkeytype = .next       self.autocorrectiontype = .no    } }  private func createbottomline() -> uiview {     // y position line    let y: cgfloat = self.placeholderlabel.frame.origin.y + self.placeholderlabel.frame.height + 4    // create frame bottom line    let bottomlineframe: rect = rect(x: 0, y: y , w: self.frame.w, h: 1)    // create bottom line    let botttomline: line = line(frame: bottomlineframe, alpha: 0.38)    // return bottom line    return botttomline  }  private func createplaceholderlabel() -> uilabel {    // create frame placeholder text   let placeholderframe: cgrect = cgrect(x: 0, y: 20, width: self.frame.width, height: 19)   // create placeholder text   let placeholder: uilabel = uilabel(frame: placeholderframe, font: self.inactivefont, align: .left, color: color().black)   // set alpha placeholder   placeholder.alpha = 0.38   // set text placeholder   placeholder.text = self.placeholdertext   // return placeholder   return placeholder   }  /**   function updates style text field   - parameter state: state text field current */ private func updatestyle(state: textfieldstate) {    switch state {   case .active:      self.activestyle()   case .inactiveblank:      print("update inactive blank state & style changes")   case .inactivetext:      print("update inactive text state , style changes")   }  }  /**   function when text field in active state , needs style accordingly */ private func activestyle() {    // create animation   let animate: () -> () = {      print("animate!!!")      self.placeholderlabel.font = self.activehintfont      self.placeholderlabel.frame.origin.y = 4      self.placeholderlabel.textcolor = self.standardcolor      self.bottomline.backgroundcolor = self.standardcolor      var newframe: cgrect = self.bottomline.frame      newframe.origin.y = 86      self.bottomline.frame = newframe   }   // animate view   uiview.animatewithduration(0.3, animations: animate)   uiview.animatewithduration(0.3, delay: 0.0, options: .curveeaseinout, animations: {      self.bottomline.frame.origin.y = 86      }, completion: nil) }     }  // mark: methods text placement extension textfield {     override func editingrectforbounds(bounds: cgrect) -> cgrect {       return textbounds    }     override func textrectforbounds(bounds: cgrect) -> cgrect {       return textbounds    }   }  // mark: delegate methods extension textfield : uitextfielddelegate {     /**     function handles when text field begins editing    */    func textfielddidbeginediting(textfield: uitextfield) {       print("i started editing")       self.updatestyle(.active)     }     /**      function handles when text field finishes editing    */    func textfielddidendediting(textfield: uitextfield) {       print("i finished editing")    }     /**       function handles when text field changes    */    func textfielddidchange(textfield: textfield) {       print("i changed")       print("text = \(self.text)")    }  } 

the animation block gets called nothing updates. view on screen , know viewwillapear has been called. cause type of issue? have tried passing animation onto thread , didn't work.

it's logic setting frame's y position. frame can set view's frame setter.

let newframe: cgrect = self.bottomline.frame; newframe.origin.y = 86; self.bottomline.frame = newframe; 

edit bottomline initializer getting called anew before animation. lazy build of view (by assigning tag) approach.