blocks|key|4498194|text|您可以通过将UITextField委托设置为视图控制器来验证文本，然后执行以下操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4498195|func+textField(textField:+UITextField,+shouldChangeCharactersInRange+range:+NSRange,+replacementString+string:+String)+->+Bool+{

+++//+Your+method+to+validate+the+input
+++//+self.validateInputText()

+++return+true
}|code-block|syntax|javascript|4498196|如果你愿意，你甚至可以改变它的边框颜色：|4498197|textField.layer.borderColor+=+UIColor.redColor().CGColor|4498198|我希望这对你有帮助。|4498199|entityMap^0|6|B|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|Y|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|R|$]]

You can validate the text by setting the <code>UITextField</code> delegate to your view controller then do something like this :

<pre><code>func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -&gt; Bool {

 // Your method to validate the input
 // self.validateInputText()

 return true
}
</code></pre>

And you can even change its border color if you want:

<pre><code>textField.layer.borderColor = UIColor.redColor().CGColor
</code></pre>

I hope this help you.

blocks|key|4497324|text|不，没有内置的方法可以做同样的事情。为此，您需要自定义UITextField。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4497325|有一些开源库可以做到这一点。你可以在这里找到一个：US2FormValidator|4497326|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/ustwo/US2FormValidator^0|R|B|0|P|G|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@$9|T|A|U|1|V]]|E|$]]|$1|H|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

No, there is no built in method available for doing the same. For that you need to customize the <code>UITextField</code>.

There are some open-source library available for doing that. You can find one here : <a href="https://github.com/ustwo/US2FormValidator" rel="nofollow">US2FormValidator</a>

blocks|key|4497418|text|UITextField没有提供开箱即用的验证功能。您可以找到一些开源API来帮助您完成此任务。一种可能的选择是研究SSValidationTextField应用编程接口。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4497419|代码应该是|4497420|var+phoneValidationTextField+=+SSValidationTextField(frame:+CGRectMake(200,+200,+150,+50))
phoneValidationTextField.validityFunction+=+self.isValidPhone
phoneValidationTextField.delaytime+=+0.5
phoneValidationTextField.errorText+=+"Incorrect+Format"
phoneValidationTextField.successText+=+"Valid+Format"
phoneValidationTextField.borderStyle+=+UITextBorderStyle.RoundedRect
self.addSubview(phoneValidationTextField)|code-block|syntax|javascript|4497421|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/shamasshahid/SSValidationTextField^0|0|B|1L|L|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|11|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

<code>UITextField</code> doesn't come with a validation function out of the box. You can find some open source APIs to help you accomplish this. One possible option would be to look into the <a href="https://github.com/shamasshahid/SSValidationTextField" rel="nofollow">SSValidationTextField</a> api. 

Code would be 

<pre><code>var phoneValidationTextField = SSValidationTextField(frame: CGRectMake(200, 200, 150, 50))
phoneValidationTextField.validityFunction = self.isValidPhone
phoneValidationTextField.delaytime = 0.5
phoneValidationTextField.errorText = "Incorrect Format"
phoneValidationTextField.successText = "Valid Format"
phoneValidationTextField.borderStyle = UITextBorderStyle.RoundedRect
self.addSubview(phoneValidationTextField)
</code></pre>

blocks|key|4498471|text|经过一天的工作，我在Swift上模拟了TextView.setError()。下面是我得到的信息：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4498472|​|4498473|📷|atomic|4498474|4498475|swift+5上的代码：|4498476|import+UIKit

private+var+rightViews+=+NSMapTable<UITextField,+UIView>(keyOptions:+NSPointerFunctions.Options.weakMemory,+valueOptions:+NSPointerFunctions.Options.strongMemory)
private+var+errorViews+=+NSMapTable<UITextField,+UIView>(keyOptions:+NSPointerFunctions.Options.weakMemory,+valueOptions:+NSPointerFunctions.Options.strongMemory)++++

extension+UITextField+{
++++//+Add/remove+error+message
++++func+setError(_+string:+String?+=+nil,+show:+Bool+=+true)+{
++++++++if+let+rightView+=+rightView,+rightView.tag+!=+999+{
++++++++++++rightViews.setObject(rightView,+forKey:+self)
++++++++}

++++++++//+Remove+message
++++++++guard+string+!=+nil+else+{
++++++++++++if+let+rightView+=+rightViews.object(forKey:+self)+{
++++++++++++++++self.rightView+=+rightView
++++++++++++++++rightViews.removeObject(forKey:+self)
++++++++++++}+else+{
++++++++++++++++self.rightView+=+nil
++++++++++++}

++++++++++++if+let+errorView+=+errorViews.object(forKey:+self)+{
++++++++++++++++errorView.isHidden+=+true
++++++++++++++++errorViews.removeObject(forKey:+self)
++++++++++++}

++++++++++++return
++++++++}

++++++++//+Create+container
++++++++let+container+=+UIView()
++++++++container.translatesAutoresizingMaskIntoConstraints+=+false

++++++++//+Create+triangle
++++++++let+triagle+=+TriangleTop()
++++++++triagle.backgroundColor+=+.clear
++++++++triagle.translatesAutoresizingMaskIntoConstraints+=+false
++++++++container.addSubview(triagle)

++++++++//+Create+red+line
++++++++let+line+=+UIView()
++++++++line.backgroundColor+=+.red
++++++++line.translatesAutoresizingMaskIntoConstraints+=+false
++++++++container.addSubview(line)

++++++++//+Create+message
++++++++let+label+=+UILabel()
++++++++label.text+=+string
++++++++label.textColor+=+.white
++++++++label.numberOfLines+=+0
++++++++label.font+=+UIFont.systemFont(ofSize:+15)
++++++++label.backgroundColor+=+.black
++++++++label.setContentCompressionResistancePriority(UILayoutPriority(rawValue:+250),+for:+.horizontal)
++++++++label.translatesAutoresizingMaskIntoConstraints+=+false
++++++++container.addSubview(label)

++++++++//+Set+constraints+for+triangle
++++++++triagle.heightAnchor.constraint(equalToConstant:+10).isActive+=+true
++++++++triagle.widthAnchor.constraint(equalToConstant:+15).isActive+=+true
++++++++triagle.topAnchor.constraint(equalTo:+container.topAnchor,+constant:+-10).isActive+=+true
++++++++triagle.trailingAnchor.constraint(equalTo:+container.trailingAnchor,+constant:+-15).isActive+=+true

++++++++//+Set+constraints+for+line
++++++++line.heightAnchor.constraint(equalToConstant:+3).isActive+=+true
++++++++line.topAnchor.constraint(equalTo:+triagle.bottomAnchor,+constant:+0).isActive+=+true
++++++++line.leadingAnchor.constraint(equalTo:+container.leadingAnchor,+constant:+0).isActive+=+true
++++++++line.trailingAnchor.constraint(equalTo:+container.trailingAnchor,+constant:+0).isActive+=+true

++++++++//+Set+constraints+for+label
++++++++label.topAnchor.constraint(equalTo:+line.bottomAnchor,+constant:+0).isActive+=+true
++++++++label.bottomAnchor.constraint(equalTo:+container.bottomAnchor,+constant:+0).isActive+=+true
++++++++label.leadingAnchor.constraint(equalTo:+container.leadingAnchor,+constant:+0).isActive+=+true
++++++++label.trailingAnchor.constraint(equalTo:+container.trailingAnchor,+constant:+0).isActive+=+true

++++++++if+!show+{
++++++++++++container.isHidden+=+true
++++++++}
++++++++//+superview!.superview!.addSubview(container)
++++++++UIApplication.shared.keyWindow!.addSubview(container)

++++++++//+Set+constraints+for+container
++++++++container.widthAnchor.constraint(lessThanOrEqualTo:+superview!.widthAnchor,+multiplier:+1).isActive+=+true
++++++++container.trailingAnchor.constraint(equalTo:+superview!.trailingAnchor,+constant:+0).isActive+=+true
++++++++container.topAnchor.constraint(equalTo:+superview!.bottomAnchor,+constant:+0).isActive+=+true

++++++++//+Hide+other+error+messages
++++++++let+enumerator+=+errorViews.objectEnumerator()
++++++++while+let+view+=+enumerator!.nextObject()+as!+UIView?+{
++++++++++++view.isHidden+=+true
++++++++}

++++++++//+Add+right+button+to+textField
++++++++let+errorButton+=+UIButton(type:+.custom)
++++++++errorButton.tag+=+999
++++++++errorButton.setImage(UIImage(named:+"ic_error"),+for:+.normal)
++++++++errorButton.frame+=+CGRect(x:+0,+y:+0,+width:+frame.size.height,+height:+frame.size.height)
++++++++errorButton.addTarget(self,+action:+#selector(errorAction),+for:+.touchUpInside)
++++++++rightView+=+errorButton
++++++++rightViewMode+=+.always

++++++++//+Save+view+with+error+message
++++++++errorViews.setObject(container,+forKey:+self)
++++}

++++//+Show+error+message
++++@IBAction
++++func+errorAction(_+sender:+Any)+{
++++++++let+errorButton+=+sender+as!+UIButton
++++++++let+textField+=+errorButton.superview+as!+UITextField

++++++++let+errorView+=+errorViews.object(forKey:+textField)
++++++++if+let+errorView+=+errorView+{
++++++++++++errorView.isHidden.toggle()
++++++++}

++++++++let+enumerator+=+errorViews.objectEnumerator()
++++++++while+let+view+=+enumerator!.nextObject()+as!+UIView?+{
++++++++++++if+view+!=+errorView+{
++++++++++++++++view.isHidden+=+true
++++++++++++}
++++++++}

++++++++//+Don't+hide+keyboard+after+click+by+icon
++++++++UIViewController.isCatchTappedAround+=+false
++++}
}

class+TriangleTop:+UIView+{
++++override+init(frame:+CGRect)+{
++++++++super.init(frame:+frame)
++++}

++++required+init?(coder+aDecoder:+NSCoder)+{
++++++++super.init(coder:+aDecoder)
++++}

++++override+func+draw(_+rect:+CGRect)+{
++++++++guard+let+context+=+UIGraphicsGetCurrentContext()+else+{
++++++++++++return
++++++++}

++++++++context.beginPath()
++++++++context.move(to:+CGPoint(x:+(rect.maxX+/+2.0),+y:+rect.minY))
++++++++context.addLine(to:+CGPoint(x:+rect.maxX,+y:+rect.maxY))
++++++++context.addLine(to:+CGPoint(x:+(rect.minX+/+2.0),+y:+rect.maxY))
++++++++context.closePath()

++++++++context.setFillColor(UIColor.red.cgColor)
++++++++context.fillPath()
++++}
}|code-block|syntax|javascript|4498477|使用方法：|4498478|class+MyViewController:+UIViewController+{
++++@IBOutlet+weak+var+emailField:+UITextField!

++++override+func+viewDidLoad()+{
++++++++super.viewDidLoad()

++++++++emailField.delegate+=+self
++++}
}

//+Validation+textFields
extension+MyViewController:+UITextFieldDelegate+{
++++//+Remove+error+message+after+start+editing
++++func+textField(_+textField:+UITextField,+shouldChangeCharactersIn+range:+NSRange,+replacementString+string:+String)+->+Bool+{
++++++++textField.setError()
++++++++return+true
++++}

++++//+Check+error
++++func+textFieldDidBeginEditing(_+textField:+UITextField)+{
++++++++Validator.isValidEmail(field:+textField)
++++}

++++//+Check+error
++++func+textFieldDidEndEditing(_+textField:+UITextField)+{
++++++++Validator.isValidEmail(field:+textField,+show:+false)
++++}
}

class+Validator+{
++++static+let+EMAIL_ADDRESS+=
++++++++"[a-zA-Z0-9\\%2B\\.\\_\\%25\\-\\%2B]{1,256}"+%2B
++++++++"\\@"+%2B
++++++++"[a-zA-Z0-9][a-zA-Z0-9\\-]{0,64}"+%2B
++++++++"("+%2B
++++++++++++"\\."+%2B
++++++++++++"[a-zA-Z0-9][a-zA-Z0-9\\-]{0,25}"+%2B
++++++++")%2B"

++++//+Validator+e-mail+from+string
++++static+func+isValidEmail(_+value:+String)+->+Bool+{
++++++++let+string+=+value.trimmingCharacters(in:+.whitespacesAndNewlines)
++++++++let+predicate+=+NSPredicate(format:+"SELF+MATCHES+%25@",+Validator.EMAIL_ADDRESS)
++++++++return+predicate.evaluate(with:+string)+%7C%7C+string.isEmpty
++++}

++++static+func+isValidEmail(field:+UITextField,+show:+Bool+=+true)+->+Bool+{
++++++++if+Validator.isValidEmail(field.text!)+{
++++++++++++field.setError()
++++++++++++return+true
++++++++}+else+{
++++++++++++field.setError("Error+message",+show:+show)
++++++++}
++++++++return+false
++++}
}|4498479|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/27de8660e6b7c8c4ed8298a9d8e66e0f.png|imageAlt^0|J|J|0|0|0|1|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|18|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@$9|1A|A|1B|1|1C]]|E|$]]|$1|K|3|G|5|6|7|1D|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|1E|8|@]|D|@]|E|$]]|$1|N|3|O|5|P|7|1F|8|@]|D|@]|E|$Q|R]]|$1|S|3|T|5|6|7|1G|8|@]|D|@]|E|$]]|$1|U|3|V|5|P|7|1H|8|@]|D|@]|E|$Q|R]]|$1|W|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|X|$Y|$5|Z|10|11|E|$12|13|14|-4]]]]

After a day of work, I made an analogue of <code>TextView.setError()</code> on Swift. Here's what I got: 

<a href="https://i.stack.imgur.com/a9TNB.png" rel="noreferrer"><img src="https://i.stack.imgur.com/a9TNB.png" alt="enter image description here"></a>

Code on swift 5:

<pre><code>import UIKit

private var rightViews = NSMapTable&lt;UITextField, UIView&gt;(keyOptions: NSPointerFunctions.Options.weakMemory, valueOptions: NSPointerFunctions.Options.strongMemory)
private var errorViews = NSMapTable&lt;UITextField, UIView&gt;(keyOptions: NSPointerFunctions.Options.weakMemory, valueOptions: NSPointerFunctions.Options.strongMemory) 

extension UITextField {
 // Add/remove error message
 func setError(_ string: String? = nil, show: Bool = true) {
 if let rightView = rightView, rightView.tag != 999 {
 rightViews.setObject(rightView, forKey: self)
 }

 // Remove message
 guard string != nil else {
 if let rightView = rightViews.object(forKey: self) {
 self.rightView = rightView
 rightViews.removeObject(forKey: self)
 } else {
 self.rightView = nil
 }

 if let errorView = errorViews.object(forKey: self) {
 errorView.isHidden = true
 errorViews.removeObject(forKey: self)
 }

 return
 }

 // Create container
 let container = UIView()
 container.translatesAutoresizingMaskIntoConstraints = false

 // Create triangle
 let triagle = TriangleTop()
 triagle.backgroundColor = .clear
 triagle.translatesAutoresizingMaskIntoConstraints = false
 container.addSubview(triagle)

 // Create red line
 let line = UIView()
 line.backgroundColor = .red
 line.translatesAutoresizingMaskIntoConstraints = false
 container.addSubview(line)

 // Create message
 let label = UILabel()
 label.text = string
 label.textColor = .white
 label.numberOfLines = 0
 label.font = UIFont.systemFont(ofSize: 15)
 label.backgroundColor = .black
 label.setContentCompressionResistancePriority(UILayoutPriority(rawValue: 250), for: .horizontal)
 label.translatesAutoresizingMaskIntoConstraints = false
 container.addSubview(label)

 // Set constraints for triangle
 triagle.heightAnchor.constraint(equalToConstant: 10).isActive = true
 triagle.widthAnchor.constraint(equalToConstant: 15).isActive = true
 triagle.topAnchor.constraint(equalTo: container.topAnchor, constant: -10).isActive = true
 triagle.trailingAnchor.constraint(equalTo: container.trailingAnchor, constant: -15).isActive = true

 // Set constraints for line
 line.heightAnchor.constraint(equalToConstant: 3).isActive = true
 line.topAnchor.constraint(equalTo: triagle.bottomAnchor, constant: 0).isActive = true
 line.leadingAnchor.constraint(equalTo: container.leadingAnchor, constant: 0).isActive = true
 line.trailingAnchor.constraint(equalTo: container.trailingAnchor, constant: 0).isActive = true

 // Set constraints for label
 label.topAnchor.constraint(equalTo: line.bottomAnchor, constant: 0).isActive = true
 label.bottomAnchor.constraint(equalTo: container.bottomAnchor, constant: 0).isActive = true
 label.leadingAnchor.constraint(equalTo: container.leadingAnchor, constant: 0).isActive = true
 label.trailingAnchor.constraint(equalTo: container.trailingAnchor, constant: 0).isActive = true

 if !show {
 container.isHidden = true
 }
 // superview!.superview!.addSubview(container)
 UIApplication.shared.keyWindow!.addSubview(container)

 // Set constraints for container
 container.widthAnchor.constraint(lessThanOrEqualTo: superview!.widthAnchor, multiplier: 1).isActive = true
 container.trailingAnchor.constraint(equalTo: superview!.trailingAnchor, constant: 0).isActive = true
 container.topAnchor.constraint(equalTo: superview!.bottomAnchor, constant: 0).isActive = true

 // Hide other error messages
 let enumerator = errorViews.objectEnumerator()
 while let view = enumerator!.nextObject() as! UIView? {
 view.isHidden = true
 }

 // Add right button to textField
 let errorButton = UIButton(type: .custom)
 errorButton.tag = 999
 errorButton.setImage(UIImage(named: "ic_error"), for: .normal)
 errorButton.frame = CGRect(x: 0, y: 0, width: frame.size.height, height: frame.size.height)
 errorButton.addTarget(self, action: #selector(errorAction), for: .touchUpInside)
 rightView = errorButton
 rightViewMode = .always

 // Save view with error message
 errorViews.setObject(container, forKey: self)
 }

 // Show error message
 @IBAction
 func errorAction(_ sender: Any) {
 let errorButton = sender as! UIButton
 let textField = errorButton.superview as! UITextField

 let errorView = errorViews.object(forKey: textField)
 if let errorView = errorView {
 errorView.isHidden.toggle()
 }

 let enumerator = errorViews.objectEnumerator()
 while let view = enumerator!.nextObject() as! UIView? {
 if view != errorView {
 view.isHidden = true
 }
 }

 // Don't hide keyboard after click by icon
 UIViewController.isCatchTappedAround = false
 }
}

class TriangleTop: UIView {
 override init(frame: CGRect) {
 super.init(frame: frame)
 }

 required init?(coder aDecoder: NSCoder) {
 super.init(coder: aDecoder)
 }

 override func draw(_ rect: CGRect) {
 guard let context = UIGraphicsGetCurrentContext() else {
 return
 }

 context.beginPath()
 context.move(to: CGPoint(x: (rect.maxX / 2.0), y: rect.minY))
 context.addLine(to: CGPoint(x: rect.maxX, y: rect.maxY))
 context.addLine(to: CGPoint(x: (rect.minX / 2.0), y: rect.maxY))
 context.closePath()

 context.setFillColor(UIColor.red.cgColor)
 context.fillPath()
 }
}

</code></pre>

How to use:

<pre><code>class MyViewController: UIViewController {
 @IBOutlet weak var emailField: UITextField!

 override func viewDidLoad() {
 super.viewDidLoad()

 emailField.delegate = self
 }
}

// Validation textFields
extension MyViewController: UITextFieldDelegate {
 // Remove error message after start editing
 func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool {
 textField.setError()
 return true
 }

 // Check error
 func textFieldDidBeginEditing(_ textField: UITextField) {
 Validator.isValidEmail(field: textField)
 }

 // Check error
 func textFieldDidEndEditing(_ textField: UITextField) {
 Validator.isValidEmail(field: textField, show: false)
 }
}

class Validator {
 static let EMAIL_ADDRESS =
 "[a-zA-Z0-9\\+\\.\\_\\%\\-\\+]{1,256}" +
 "\\@" +
 "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,64}" +
 "(" +
 "\\." +
 "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,25}" +
 ")+"

 // Validator e-mail from string
 static func isValidEmail(_ value: String) -&gt; Bool {
 let string = value.trimmingCharacters(in: .whitespacesAndNewlines)
 let predicate = NSPredicate(format: "SELF MATCHES %@", Validator.EMAIL_ADDRESS)
 return predicate.evaluate(with: string) || string.isEmpty
 }

 static func isValidEmail(field: UITextField, show: Bool = true) -&gt; Bool {
 if Validator.isValidEmail(field.text!) {
 field.setError()
 return true
 } else {
 field.setError("Error message", show: show)
 }
 return false
 }
}
</code></pre>

blocks|key|4498520|text|extension+UITextField+{


/**
this+function+adds+a+right+view+on+the+text+field
*/


func+addRightView(rightView:+String,+tintColor:+UIColor?+=+nil,+errorMessage:+String?+=+nil)+{
++++if+rightView+!=+""+{
++++++++let+rightview+=+UIButton(type:+.custom)
++++++++
++++++++if+tintColor+!=+nil+{
++++++++++++let+templateImage+=+UIImage(named:+rightView)?.withRenderingMode(UIImage.RenderingMode.alwaysTemplate)
++++++++++++rightview.setImage(templateImage,+for:+.normal)
++++++++++++rightview.tintColor+=+tintColor
++++++++}
++++++++else{
++++++++++++rightview.setImage(UIImage(named:+rightView),+for:+.normal)
++++++++}
++++++++
++++++++if+let+message+=+errorMessage+{
++++++++++++rightview.imageEdgeInsets+=+UIEdgeInsets(top:+0,+left:+-16,+bottom:+5,+right:+0)
++++++++++++showErrorView(errorMessage:+message)
++++++++}+else+{
++++++++++++rightview.imageEdgeInsets+=+UIEdgeInsets(top:+0,+left:+-16,+bottom:+0,+right:+0)
++++++++}
++++++++
++++++++self.rightViewMode+=+.always
++++++++self.rightView+=+rightview
++++}
++++else{
++++++++self.rightView+=+.none
++++++++for+vw+in+self.subviews+where+vw.tag+==+1000+{
++++++++++++vw.removeFromSuperview()
++++++++}
++++}
}

/**
+this+function+add+custom+alert+as+a+right+view+on+the+text+field
+*/

private+func+showErrorView(errorMessage:+String)+{
++++
++++let+containerVw+=+UIView(frame:+CGRect(x:+self.frame.origin.x+%2B+30,+y:+30,+width:+self.frame.size.width+-+60,+height:+45))
++++containerVw.backgroundColor+=+.clear
++++containerVw.tag+=+1000
++++
++++let+triangleVw+=+UIButton(frame:+CGRect(x:+containerVw.frame.maxX+-+25,+y:+0,+width:+15,+height:+15))
++++triangleVw.isUserInteractionEnabled+=+false
++++triangleVw.setImage(UIImage(named:+"arrowUp"),+for:+.normal)
++++triangleVw.imageEdgeInsets+=+UIEdgeInsets(top:+3,+left:+0,+bottom:+0,+right:+0)
++++triangleVw.tintColor+=+AppColor.red1
++++
++++let+messageVw+=+UIView(frame:+CGRect(x:+containerVw.frame.origin.x,+y:+triangleVw.frame.maxY+-+2,+width:+containerVw.frame.width,+height:+30))
++++messageVw.backgroundColor+=+UIColor.red
++++
++++let+errorLbl+=+UILabel(frame:+CGRect(x:+0,+y:+2,+width:+messageVw.frame.size.width,+height:+messageVw.frame.size.height+-+2))
++++errorLbl.backgroundColor+=+.black
++++errorLbl.numberOfLines+=+2
++++messageVw.addSubview(errorLbl)
++++errorLbl.text+=+errorMessage
++++errorLbl.textColor+=+.white
++++errorLbl.textAlignment+=+.left
++++errorLbl.font+=+UIFont.systemFont(ofSize:+14)
++++
++++containerVw.addSubview(triangleVw)
++++containerVw.sendSubviewToBack(triangleVw)
++++containerVw.addSubview(messageVw)
++++containerVw.layoutIfNeeded()
++++
++++self.addSubview(containerVw)
++++self.bringSubviewToFront(containerVw)
}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4498521|用法：|unstyled|4498522|rightView是镜像名称，根据您的要求传递any。如果要删除右视图，请设置为空。|offset|length|style|CODE|4498523|tintColor是可选的，可根据您的要求使用任何。|4498524|设置message+(如果您想要像安卓一样显示错误消息，则设置message的值为errorMessage)。|4498525|删除RightView|4498526|textField.addRightView(rightView:+"")|4498527|添加RightView|4498528|textField.addRightView(rightView:+"rightVwWarning",+tintColor:+UIColor.red)|4498529|添加RightView和错误信息作为android|4498530|textField.addRightView(rightView:+"rightVwWarning",+tintColor:+UIColor.red,+errorMessage:+"Error")|4498531|entityMap^0|0|0|0|9|0|0|9|0|15|D|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|15|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|16|8|@$I|17|J|18|K|L]]|9|@]|A|$]]|$1|M|3|N|5|F|7|19|8|@$I|1A|J|1B|K|L]]|9|@]|A|$]]|$1|O|3|P|5|F|7|1C|8|@$I|1D|J|1E|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|F|7|1F|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1G|8|@]|9|@]|A|$B|C]]|$1|U|3|V|5|F|7|1H|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1I|8|@]|9|@]|A|$B|C]]|$1|Y|3|Z|5|F|7|1J|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1K|8|@]|9|@]|A|$B|C]]|$1|12|3|-4|5|F|7|1L|8|@]|9|@]|A|$]]]|13|$]]

<pre><code>extension UITextField {


/**
this function adds a right view on the text field
*/


func addRightView(rightView: String, tintColor: UIColor? = nil, errorMessage: String? = nil) {
 if rightView != &quot;&quot; {
 let rightview = UIButton(type: .custom)
 
 if tintColor != nil {
 let templateImage = UIImage(named: rightView)?.withRenderingMode(UIImage.RenderingMode.alwaysTemplate)
 rightview.setImage(templateImage, for: .normal)
 rightview.tintColor = tintColor
 }
 else{
 rightview.setImage(UIImage(named: rightView), for: .normal)
 }
 
 if let message = errorMessage {
 rightview.imageEdgeInsets = UIEdgeInsets(top: 0, left: -16, bottom: 5, right: 0)
 showErrorView(errorMessage: message)
 } else {
 rightview.imageEdgeInsets = UIEdgeInsets(top: 0, left: -16, bottom: 0, right: 0)
 }
 
 self.rightViewMode = .always
 self.rightView = rightview
 }
 else{
 self.rightView = .none
 for vw in self.subviews where vw.tag == 1000 {
 vw.removeFromSuperview()
 }
 }
}

/**
 this function add custom alert as a right view on the text field
 */

private func showErrorView(errorMessage: String) {
 
 let containerVw = UIView(frame: CGRect(x: self.frame.origin.x + 30, y: 30, width: self.frame.size.width - 60, height: 45))
 containerVw.backgroundColor = .clear
 containerVw.tag = 1000
 
 let triangleVw = UIButton(frame: CGRect(x: containerVw.frame.maxX - 25, y: 0, width: 15, height: 15))
 triangleVw.isUserInteractionEnabled = false
 triangleVw.setImage(UIImage(named: &quot;arrowUp&quot;), for: .normal)
 triangleVw.imageEdgeInsets = UIEdgeInsets(top: 3, left: 0, bottom: 0, right: 0)
 triangleVw.tintColor = AppColor.red1
 
 let messageVw = UIView(frame: CGRect(x: containerVw.frame.origin.x, y: triangleVw.frame.maxY - 2, width: containerVw.frame.width, height: 30))
 messageVw.backgroundColor = UIColor.red
 
 let errorLbl = UILabel(frame: CGRect(x: 0, y: 2, width: messageVw.frame.size.width, height: messageVw.frame.size.height - 2))
 errorLbl.backgroundColor = .black
 errorLbl.numberOfLines = 2
 messageVw.addSubview(errorLbl)
 errorLbl.text = errorMessage
 errorLbl.textColor = .white
 errorLbl.textAlignment = .left
 errorLbl.font = UIFont.systemFont(ofSize: 14)
 
 containerVw.addSubview(triangleVw)
 containerVw.sendSubviewToBack(triangleVw)
 containerVw.addSubview(messageVw)
 containerVw.layoutIfNeeded()
 
 self.addSubview(containerVw)
 self.bringSubviewToFront(containerVw)
}
}
</code></pre>
<h3>Usage:</h3>
<code>rightView</code> is the image name pass any as per your requirement. Set empty if you want to remove right view.
<code>tintColor</code> is optional to use any as per your requirement.
Set message (<code>errorMessage)</code> value if you want to show an error message like an android.
Remove RightView
<pre><code>textField.addRightView(rightView: &quot;&quot;)
</code></pre>
Add RightView
<pre><code>textField.addRightView(rightView: &quot;rightVwWarning&quot;, tintColor: UIColor.red)
</code></pre>
Add RightView and error message as android
<pre><code>textField.addRightView(rightView: &quot;rightVwWarning&quot;, tintColor: UIColor.red, errorMessage: &quot;Error&quot;)
</code></pre>

Is there a way to show a validation error on a <code>UITextField</code> which is similar to Android's <code>TextView.setError()</code> in swift?

Displaying validation error on iOS UITextField similar to Android's TextView.setError()

Swift

有没有办法在类似于swift中安卓TextView.setError()的UITextField上显示验证错误？

问在类似于安卓TextView.setError()的iOS UITextField上显示验证错误
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