这是一个关于一个很好的项目来源，它可以实现你的搜索：

  public enum EGFloatingTextFieldValidationType { 
案例电子邮件
案例编号
} 

公共类EGFloatingTextField：UITextField {


私有类型EGFloatingTextFieldValidationBlock =（（text ：String，inout message：String） - >布尔）！ 

 public var validationType：EGFloatingTextFieldValidationType！ 


 private var emailValidationBlock：EGFloatingTextFieldValidationBlock 
 private var numberValidationBlock：EGFloatingTextFieldValidationBlock 


 let kDefaultInactiveColor = UIColor（white：CGFloat（0）， alpha：CGFloat（0.54））
让kDefaultActiveColor = UIColor.blueColor（）
让kDefaultErrorColor = UIColor.redColor（）
让kDefaultLineHeight = CGFloat（22）
让kDefaultLabelTextColor = UIColor （白色：CGFloat（0），alpha：CGFloat（0.54））


 public var floatingLabel：Bool！ 
 var label：UILabel！ 
 var labelFont：UIFont！ 
 var labelTextColor：UIColor！ 
 var activeBorder：UIView！ 
 var floating：Bool！ 
 var active：Bool！ 
 var hasError：Bool！ 
 var errorMessage：String！ 



必需public init（编码器aDecoder：NSCoder）{
 super.init（编码器：aDecoder）
 self.commonInit（）
} 


覆盖public init（frame：CGRect）{
 super.init（frame：frame）
 self.commonInit（）
} 

 func commonInit（）{

 self.emailValidationBlock =（{（text：String，inout message：String） - > Bool in 
 var emailRegex =[ A-Z0-9a-z ._％+  - ] + @ [A-Za-z0-9 .-] + \\。[A-Za-z] {2,6}

 var emailTest = NSPredicate（格式：SELF MATCHES％@，emailRegex）

 var isValid = emailTest.evaluateWithObject（text）
 if！isValid {
 message = 无效的电子邮件地址
} 
返回isValid; 
}）
 self.numberValidationBlock =（{（text：String，inout message：String） - >布尔在
 var numRegex =[0-9。+  - ] +; 
 var numTest = NSPredicate（格式：SELF MATCHES％@，numRegex）

 var isValid = numTest.evaluateWithObject（text）
 if！isValid {
 message =无效数字
} 
返回isValid; 

}）
 self.floating = false 
 self.hasError = false 

 self.labelTextColor = kDefaultLabelTextColor 
 self.label = UILabel （框架：CGRectZero）
 self.label.font = self.labelFont 
 self.label.textColor = self.labelTextColor 
 self.label.textAlignment = NSTextAlignment.Left 
 self。 label.numberOfLines = 1 
 self.label.layer.masksToBounds = false 
 self.addSubview（self.label）


 self.activeBorder = UIView（frame： CGRectZero）
 self.activeBorder.backgroundColor = kDefaultActiveColor 
 self.activeBorder.layer.opacity = 0 
 self.addSubview（self.activeBorder）

 self.label。 autoAlignAxis（ALAxis.Horizo​​ntal，toSameAxisOfView：self）
 self.label.autoPinEdge（ALEdge.Left，toEdge：ALEdge.Left，ofView：self）
 self.label.autoMatchDimension（ALDimension.Width，toDimension：ALDimension.Width，ofView：self）
 self.label.autoMatchDimension（ALDimension.Height，toDimension：ALDimension.Height，ofView：self）

 self.activeBorder.autoPinEdge（ALEdge.Bottom，toEdge：ALEdge.Bottom，ofView：self）
 self.activeBorder.autoPinEdge（ALEdge.Left，toEdge：ALEdge.Left，ofView：self）
 self.activeBorder.autoPinEdge（ALEdge.Right，toEdge：ALEdge.Right，ofView：self）
 self.activeBorder.autoSetDimension（ALDimension.Height，toSize：2）

 NSNotificationCenter.defaultCenter（ ）.addObserver（self，selector：Selector（textDidChange：），name：UITextFieldTextDidChangeNotification，object：self）
} 
 public func setPlaceHolder（placeholder：String）{
 self。 label.text =占位符
} 

覆盖公共func成员FirstFirstResponder（） - > Bool {

 var flag：bool = super.becomeFirstResponder（）

 if flag {

 if self.floatingLabel！ {

 if！self.floating！ || self.text！.isEmpty {
 self.floatLabelToTop（）
 self.floating = true 
} 
} else {
 self.label.textColor = kDefaultActiveColor 
 self.label.layer.opacity = 0 
} 
 self.showActiveBorder（）
} 

 self.active = flag 
 return flag 
} 
覆盖public func resignFirstResponder（） - > Bool {

 var flag：bool = super.becomeFirstResponder（）

 if flag {

 if self.floatingLabel！ {

 if self.floating！ &安培;&安培; self.text！.isEmpty {
 self.animateLabelBack（）
 self.floating = false 
} 
} else {
 if self.text！.isEmpty {
 self.label.layer.opacity = 1 
} 
} 
 self.label.textColor = kDefaultInactiveColor 
 self.showInactiveBorder（）
 self.validate（ ）
} 
 self.active = flag 
 return flag 

} 

覆盖public func drawRect（rect：CGRect）{
 super.drawRect（rect）

 var borderColor = self.hasError！ ？ kDefaultErrorColor：kDefaultInactiveColor 

 var textRect = self.textRectForBounds（rect）
 var context = UIGraphicsGetCurrentContext（）
 var borderlines：[CGPoint] = [CGPointMake（0，CGRectGetHeight（textRect） -  1），
 CGPointMake（CGRectGetWidth（textRect），CGRectGetHeight（textRect） -  1）] 

 if self.enabled {

 CGContextBeginPath（context）; 
 CGContextAddLines（context，borderlines，2）; 
 CGContextSetLineWidth（context，1.0）; 
 CGContextSetStrokeColorWithColor（context，borderColor.CGColor）; 
 CGContextStrokePath（context）; 

} else {

 CGContextBeginPath（context）; 
 CGContextAddLines（context，borderlines，2）; 
 CGContextSetLineWidth（context，1.0）; 
 var dashPattern：[CGFloat] = [2,4] 
 CGContextSetLineDash（context，0，dashPattern，2）; 
 CGContextSetStrokeColorWithColor（context，borderColor.CGColor）; 
 CGContextStrokePath（context）; 

} 
} 

 func textDidChange（notif：NSNotification）{
 self.validate（）
} 

 func floatLabelToTop（）{

 CATransaction.begin（）
 CATransaction.setCompletionBlock {（） - >无效
 self.label.textColor = self.kDefaultActiveColor 
} 

 var anim2 = CABasicAnimation（keyPath：transform）
 var fromTransform = CATransform3DMakeScale（CGFloat（ 1.0），CGFloat（1.0），CGFloat（1））
 var toTransform = CATransform3DMakeScale（CGFloat（0.5），CGFloat（0.5），CGFloat（1））
 toTransform = CATransform3DTranslate（toTransform，-CGRectGetWidth（ self.label.frame）/ 2，-CGRectGetHeight（self.label.frame），0）
 anim2.fromValue = NSValue（CATransform3D：fromTransform）
 anim2.toValue = NSValue（CATransform3D：toTransform）
 anim2.timingFunction = CAMediaTimingFunction（name：kCAMediaTimingFunctionEaseOut）
 var animGroup = CAAnimationGroup（）
 animGroup.animations = [anim2] 
 animGroup.duration = 0.3 
 animGroup.fillMode = kCAFillModeForwards; 
 animGroup.removedOnCompletion = false; 
 self.label.layer.addAnimation（animGroup，forKey：_ floatingLabel）
 self.clipsToBounds = false 
 CATransaction.commit（）
} 
 func showActiveBorder（ ）{

 self.activeBorder.layer.transform = CATransform3DMakeScale（CGFloat（0.01），CGFloat（1.0），1）
 self.activeBorder.layer.opacity = 1 
 CATransaction .begin（）
 self.activeBorder.layer.transform = CATransform3DMakeScale（CGFloat（0.01），CGFloat（1.0），1）
 var anim2 = CABasicAnimation（keyPath：transform）
 var fromTransform = CATransform3DMakeScale（CGFloat（0.01），CGFloat（1.0），1）
 var toTransform = CATransform3DMakeScale（CGFloat（1.0），CGFloat（1.0），1）
 anim2.fromValue = NSValue（CATransform3D：fromTransform ）
 anim2.toValue = NSValue（CATransform3D：toTransform）
 anim2.timingFunction = CAMediaTimingFunction（name：kCAMe） diaTimingFunctionEaseOut）
 anim2.fillMode = kCAFillModeForwards 
 anim2.removedOnCompletion = false 
 self.activeBorder.layer.addAnimation（anim2，forKey：_ activeBorder）
 CATransaction.commit（）
} 

 func animateLabelBack（）{
 CATransaction.begin（）
 CATransaction.setCompletionBlock {（） - >无效
 self.label.textColor = self.kDefaultInactiveColor 
} 

 var anim2 = CABasicAnimation（keyPath：transform）
 var fromTransform = CATransform3DMakeScale（0.5， 0.5,1）
 fromTransform = CATransform3DTranslate（fromTransform，-CGRectGetWidth（self.label.frame）/ 2，-CGRectGetHeight（self.label.frame），0）; 
 var toTransform = CATransform3DMakeScale（1.0,1.0,1）
 anim2.fromValue = NSValue（CATransform3D：fromTransform）
 anim2.toValue = NSValue（CATransform3D：toTransform）
 anim2.timingFunction = CAMediaTimingFunction（name：kCAMediaTimingFunctionEaseOut）

 var animGroup = CAAnimationGroup（）
 animGroup.animations = [anim2] 
 animGroup.duration = 0.3 
 animGroup.fillMode = kCAFillModeForwards ; 
 animGroup.removedOnCompletion = false; 

 self.label.layer.addAnimation（animGroup，forKey：_ animateLabelBack）
 CATransaction.commit（）
} 
 func showInactiveBorder（）{

 CATransaction.begin（）
 CATransaction.setCompletionBlock {（） - >无效
 self.activeBorder.layer.opacity = 0 
} 
 var anim2 = CABasicAnimation（keyPath：transform）
 var fromTransform = CATransform3DMakeScale（1.0,1.0,1） 
 var toTransform = CATransform3DMakeScale（0.01,1.0,1）
 anim2.fromValue = NSValue（CATransform3D：fromTransform）
 anim2.toValue = NSValue（CATransform3D：toTransform）
 anim2.timingFunction = CAMediaTimingFunction（name：kCAMediaTimingFunctionEaseOut）
 anim2.fillMode = kCAFillModeForwards 
 anim2.removedOnCompletion = false 
 self.activeBorder.layer.addAnimation（anim2，forKey：_ activeBorder）
 CATransaction .commit（）
} 

 func performValidation（isValid：Bool，message：String）{
 if！isValid {
 self.hasError = true 
 self.errorMessage =消息
s elf.labelTextColor = kDefaultErrorColor 
 self.activeBorder.backgroundColor = kDefaultErrorColor 
 self.setNeedsDisplay（）
} else {
 self.hasError = false 
 self.errorMessage = nil 
 self.labelTextColor = kDefaultActiveColor 
 self.activeBorder.backgroundColor = kDefaultActiveColor 
 self.setNeedsDisplay（）
} 
} 

 func validate（ ）{

 if self.validationType！= nil {
 var message：String =

 if self.validationType！ == .Email {

 var isValid = self.emailValidationBlock（text：self.text，message：& message）

 performValidation（isValid，message：message）

} else {
 var isValid = self.numberValidationBlock（text：self.text，message：& message）

 performValidation（isValid，message：message）
} 
} 
} 


} 

扩展名EGFloatingTextField {

} 
 

他的名字是 EGFloatingTextField 你可以找到更多细节

I am pretty new to animating in Swift and have an idea of how to go about this but would like to see how others would do it -

I am trying to create the effect where the placeholder text of a search bar shrinks and moves up above the search field and changes to different color when user goes to enter search bar. Like this:

http://magicus.xyz when you click on username.

If I place a uilabel over a search bar and scale this label on entering the searcher Im not sure entering the search bar would register because a uilabel would be over it..

I am generally trying to replicate those textfields in general. How would I go about creating this animation? Or even adding a bottom border to my search bar?

Bridger:

//
//  Makestagram-Bridging-Header.h
//  round
//
//  Created by Skylar Thomas on 6/24/16.
//  Copyright © 2016 Make School. All rights reserved.
//

#ifndef Makestagram_Bridging_Header_h
#define Makestagram_Bridging_Header_h

#import "PureLayout.h"

#endif /* Makestagram_Bridging_Header_h */

ERROR:

My project:

This is the source about a nice project that achieve exactly what your search:

    public enum EGFloatingTextFieldValidationType {
        case Email
        case Number
    }

    public class EGFloatingTextField: UITextField {


        private typealias EGFloatingTextFieldValidationBlock = ((text:String,inout message:String)-> Bool)!

        public var validationType : EGFloatingTextFieldValidationType!


        private var emailValidationBlock  : EGFloatingTextFieldValidationBlock
        private var numberValidationBlock : EGFloatingTextFieldValidationBlock


        let kDefaultInactiveColor = UIColor(white: CGFloat(0), alpha: CGFloat(0.54))
        let kDefaultActiveColor = UIColor.blueColor()
        let kDefaultErrorColor = UIColor.redColor()
        let kDefaultLineHeight = CGFloat(22)
        let kDefaultLabelTextColor = UIColor(white: CGFloat(0), alpha: CGFloat(0.54))


        public var floatingLabel : Bool!
        var label : UILabel!
        var labelFont : UIFont!
        var labelTextColor : UIColor!
        var activeBorder : UIView!
        var floating : Bool!
        var active : Bool!
        var hasError : Bool!
        var errorMessage : String!



        required public init(coder aDecoder: NSCoder) {
            super.init(coder: aDecoder)
            self.commonInit()
        }


        override public init(frame: CGRect) {
            super.init(frame: frame)
            self.commonInit()
        }

        func commonInit(){

            self.emailValidationBlock = ({(text:String, inout message: String) -> Bool in
                var emailRegex = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,6}"

                var emailTest = NSPredicate(format:"SELF MATCHES %@" , emailRegex)

                var  isValid = emailTest.evaluateWithObject(text)
                if !isValid {
                    message = "Invalid Email Address"
                }
                return isValid;
            })
            self.numberValidationBlock = ({(text:String,inout message: String) -> Bool in
                var numRegex = "[0-9.+-]+";
                var numTest = NSPredicate(format:"SELF MATCHES %@" , numRegex)

                var isValid =  numTest.evaluateWithObject(text)
                if !isValid {
                    message = "Invalid Number"
                }
                return isValid;

            })
            self.floating = false
            self.hasError = false

            self.labelTextColor = kDefaultLabelTextColor
            self.label = UILabel(frame: CGRectZero)
            self.label.font = self.labelFont
            self.label.textColor = self.labelTextColor
            self.label.textAlignment = NSTextAlignment.Left
            self.label.numberOfLines = 1
            self.label.layer.masksToBounds = false
            self.addSubview(self.label)


            self.activeBorder = UIView(frame: CGRectZero)
            self.activeBorder.backgroundColor = kDefaultActiveColor
            self.activeBorder.layer.opacity = 0
            self.addSubview(self.activeBorder)

            self.label.autoAlignAxis(ALAxis.Horizontal, toSameAxisOfView: self)
            self.label.autoPinEdge(ALEdge.Left, toEdge: ALEdge.Left, ofView: self)
            self.label.autoMatchDimension(ALDimension.Width, toDimension: ALDimension.Width, ofView: self)
            self.label.autoMatchDimension(ALDimension.Height, toDimension: ALDimension.Height, ofView: self)

            self.activeBorder.autoPinEdge(ALEdge.Bottom, toEdge: ALEdge.Bottom, ofView: self)
            self.activeBorder.autoPinEdge(ALEdge.Left, toEdge: ALEdge.Left, ofView: self)
            self.activeBorder.autoPinEdge(ALEdge.Right, toEdge: ALEdge.Right, ofView: self)
            self.activeBorder.autoSetDimension(ALDimension.Height, toSize: 2)

            NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("textDidChange:"), name: "UITextFieldTextDidChangeNotification", object: self)
        }
        public func setPlaceHolder(placeholder:String){
            self.label.text = placeholder
        }

        override public func becomeFirstResponder() -> Bool {

            var flag:Bool = super.becomeFirstResponder()

            if flag {

                if self.floatingLabel! {

                    if !self.floating! || self.text!.isEmpty {
                        self.floatLabelToTop()
                        self.floating = true
                    }
                } else {
                    self.label.textColor = kDefaultActiveColor
                    self.label.layer.opacity = 0
                }
                self.showActiveBorder()
            }

            self.active=flag
            return flag
        }
        override public func resignFirstResponder() -> Bool {

            var flag:Bool = super.becomeFirstResponder()

            if flag {

                if self.floatingLabel! {

                    if self.floating! && self.text!.isEmpty {
                        self.animateLabelBack()
                        self.floating = false
                    }
                } else {
                    if self.text!.isEmpty {
                        self.label.layer.opacity = 1
                    }
                }
                self.label.textColor = kDefaultInactiveColor
                self.showInactiveBorder()
                self.validate()
            }
            self.active = flag
            return flag

        }

        override public func drawRect(rect: CGRect){
            super.drawRect(rect)

            var borderColor = self.hasError! ? kDefaultErrorColor : kDefaultInactiveColor

            var textRect = self.textRectForBounds(rect)
            var context = UIGraphicsGetCurrentContext()
            var borderlines : [CGPoint] = [CGPointMake(0, CGRectGetHeight(textRect) - 1),
                CGPointMake(CGRectGetWidth(textRect), CGRectGetHeight(textRect) - 1)]

            if  self.enabled  {

                CGContextBeginPath(context);
                CGContextAddLines(context, borderlines, 2);
                CGContextSetLineWidth(context, 1.0);
                CGContextSetStrokeColorWithColor(context, borderColor.CGColor);
                CGContextStrokePath(context);

            } else {

                CGContextBeginPath(context);
                CGContextAddLines(context, borderlines, 2);
                CGContextSetLineWidth(context, 1.0);
                var  dashPattern : [CGFloat]  = [2, 4]
                CGContextSetLineDash(context, 0, dashPattern, 2);
                CGContextSetStrokeColorWithColor(context, borderColor.CGColor);
                CGContextStrokePath(context);

            }
        }

        func textDidChange(notif: NSNotification){
            self.validate()
        }

        func floatLabelToTop() {

            CATransaction.begin()
            CATransaction.setCompletionBlock { () -> Void in
                self.label.textColor = self.kDefaultActiveColor
            }

            var anim2 = CABasicAnimation(keyPath: "transform")
            var fromTransform = CATransform3DMakeScale(CGFloat(1.0), CGFloat(1.0), CGFloat(1))
            var toTransform = CATransform3DMakeScale(CGFloat(0.5), CGFloat(0.5), CGFloat(1))
            toTransform = CATransform3DTranslate(toTransform, -CGRectGetWidth(self.label.frame)/2, -CGRectGetHeight(self.label.frame), 0)
            anim2.fromValue = NSValue(CATransform3D: fromTransform)
            anim2.toValue = NSValue(CATransform3D: toTransform)
            anim2.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
            var animGroup = CAAnimationGroup()
            animGroup.animations = [anim2]
            animGroup.duration = 0.3
            animGroup.fillMode = kCAFillModeForwards;
            animGroup.removedOnCompletion = false;
            self.label.layer.addAnimation(animGroup, forKey: "_floatingLabel")
            self.clipsToBounds = false
            CATransaction.commit()
        }
        func showActiveBorder() {

            self.activeBorder.layer.transform = CATransform3DMakeScale(CGFloat(0.01), CGFloat(1.0), 1)
            self.activeBorder.layer.opacity = 1
            CATransaction.begin()
            self.activeBorder.layer.transform = CATransform3DMakeScale(CGFloat(0.01), CGFloat(1.0), 1)
            var anim2 = CABasicAnimation(keyPath: "transform")
            var fromTransform = CATransform3DMakeScale(CGFloat(0.01), CGFloat(1.0), 1)
            var toTransform = CATransform3DMakeScale(CGFloat(1.0), CGFloat(1.0), 1)
            anim2.fromValue = NSValue(CATransform3D: fromTransform)
            anim2.toValue = NSValue(CATransform3D: toTransform)
            anim2.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
            anim2.fillMode = kCAFillModeForwards
            anim2.removedOnCompletion = false
            self.activeBorder.layer.addAnimation(anim2, forKey: "_activeBorder")
            CATransaction.commit()
        }

        func animateLabelBack() {
            CATransaction.begin()
            CATransaction.setCompletionBlock { () -> Void in
                self.label.textColor = self.kDefaultInactiveColor
            }

            var anim2 = CABasicAnimation(keyPath: "transform")
            var fromTransform = CATransform3DMakeScale(0.5, 0.5, 1)
            fromTransform = CATransform3DTranslate(fromTransform, -CGRectGetWidth(self.label.frame)/2, -CGRectGetHeight(self.label.frame), 0);
            var toTransform = CATransform3DMakeScale(1.0, 1.0, 1)
            anim2.fromValue = NSValue(CATransform3D: fromTransform)
            anim2.toValue = NSValue(CATransform3D: toTransform)
            anim2.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)

            var animGroup = CAAnimationGroup()
            animGroup.animations = [anim2]
            animGroup.duration = 0.3
            animGroup.fillMode = kCAFillModeForwards;
            animGroup.removedOnCompletion = false;

            self.label.layer.addAnimation(animGroup, forKey: "_animateLabelBack")
            CATransaction.commit()
        }
        func showInactiveBorder() {

            CATransaction.begin()
            CATransaction.setCompletionBlock { () -> Void in
                self.activeBorder.layer.opacity = 0
            }
            var anim2 = CABasicAnimation(keyPath: "transform")
            var fromTransform = CATransform3DMakeScale(1.0, 1.0, 1)
            var toTransform = CATransform3DMakeScale(0.01, 1.0, 1)
            anim2.fromValue = NSValue(CATransform3D: fromTransform)
            anim2.toValue = NSValue(CATransform3D: toTransform)
            anim2.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
            anim2.fillMode = kCAFillModeForwards
            anim2.removedOnCompletion = false
            self.activeBorder.layer.addAnimation(anim2, forKey: "_activeBorder")
            CATransaction.commit()
        }

        func performValidation(isValid:Bool,message:String){
            if !isValid {
                self.hasError = true
                self.errorMessage = message
                self.labelTextColor = kDefaultErrorColor
                self.activeBorder.backgroundColor = kDefaultErrorColor
                self.setNeedsDisplay()
            } else {
                self.hasError = false
                self.errorMessage = nil
                self.labelTextColor = kDefaultActiveColor
                self.activeBorder.backgroundColor = kDefaultActiveColor
                self.setNeedsDisplay()
            }
        }

        func validate(){

            if self.validationType != nil {
                var message : String = ""

                if self.validationType! == .Email {

                    var isValid = self.emailValidationBlock(text: self.text, message: &message)

                    performValidation(isValid,message: message)

                } else {
                    var isValid = self.numberValidationBlock(text: self.text, message: &message)

                    performValidation(isValid,message: message)
                }
            }
        }


    }

    extension EGFloatingTextField {

    }

His name is EGFloatingTextField and you can find more details here

Usage:

let emailLabel = EGFloatingTextField(frame: CGRectMake(8, 64, CGRectGetWidth(self.view.bounds) - 16, 48))
emailLabel.floatingLabel = true
emailLabel.setPlaceHolder("Email")
emailLabel.validationType = .Email
emailLabel.keyboardType = .EmailAddress
self.view.addSubview(emailLabel)

P.S. You need to import PureLayout library, here you can find the full source and instruction to how to import it.