blocks|key|237363|text|这就是您如何处理单点登录验证字段上的问题，如果需要，您可以修改最大长度并删除检查键盘类型的if语句。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|237364|还有一种逻辑可以在用户键入而不是粘贴数据时抑制最大长度警报。|237365|在这段代码的上下文中，presentAlert()/presentAlert:只是一些基本函数，它使用传递的消息字符串呈现UIAlertController+(或遗留UIAlertView)。|237366|Swift+5|237367|//+NOTE:+This+code+assumes+you+have+set+the+UITextField(s)'s+delegate+property+to+the+
//+object+that+will+contain+this+code,+because+otherwise+it+would+never+be+called.
//
//+There+are+also+some+better+stylistic+approaches+in+Swift+to+avoid+all+the+
//+nested+statements,+but+I+wanted+to+keep+the+styles+similar+to+allow+others+
//+to+contrast+and+compare+between+the+two+languages+a+little+easier.

func+textField(_+textField:+UITextField,+shouldChangeCharactersIn+range:+NSRange,+replacementString+string:+String)+->+Bool+{

++++//+Handle+backspace/delete
++++guard+!string.isEmpty+else+{

++++++++//+Backspace+detected,+allow+text+change,+no+need+to+process+the+text+any+further
++++++++return+true
++++}

++++//+Input+Validation
++++//+Prevent+invalid+character+input,+if+keyboard+is+numberpad
++++if+textField.keyboardType+==+.numberPad+{

++++++++//+Check+for+invalid+input+characters
++++++++if+CharacterSet(charactersIn:+"0123456789").isSuperset(of:+CharacterSet(charactersIn:+string))+{

++++++++++++//+Present+alert+so+the+user+knows+what+went+wrong
++++++++++++presentAlert("This+field+accepts+only+numeric+entries.")

++++++++++++//+Invalid+characters+detected,+disallow+text+change
++++++++++++return+false
++++++++}
++++}

++++//+Length+Processing
++++//+Need+to+convert+the+NSRange+to+a+Swift-appropriate+type
++++if+let+text+=+textField.text,+let+range+=+Range(range,+in:+text)+{

++++++++let+proposedText+=+text.replacingCharacters(in:+range,+with:+string)

++++++++//+Check+proposed+text+length+does+not+exceed+max+character+count
++++++++guard+proposedText.count+<=+maxCharacters+else+{

++++++++++++//+Present+alert+if+pasting+text
++++++++++++//+easy:+pasted+data+has+a+length+greater+than+1;+who+copy/pastes+one+character?
++++++++++++if+string.count+>+1+{

++++++++++++++++//+Pasting+text,+present+alert+so+the+user+knows+what+went+wrong
++++++++++++++++presentAlert("Paste+failed:+Maximum+character+count+exceeded.")
++++++++++++}

++++++++++++//+Character+count+exceeded,+disallow+text+change
++++++++++++return+false
++++++++}

++++++++//+Only+enable+the+OK/submit+button+if+they+have+entered+all+numbers+for+the+last+four
++++++++//+of+their+SSN+(prevents+early+submissions/trips+to+authentication+server,+etc)
++++++++answerButton.isEnabled+=+(proposedText.count+==+4)
++++}

++++//+Allow+text+change
++++return+true
}|code-block|syntax|javascript|237368|Objective-C|237369|//+NOTE:+This+code+assumes+you+have+set+the+UITextField(s)'s+delegate+property+to+the+
//+object+that+will+contain+this+code,+because+otherwise+it+would+never+be+called.

-+(BOOL)textField:(UITextField+*)textField+shouldChangeCharactersInRange:(NSRange)range+replacementString:(NSString+*)string
{
++++//+Handle+backspace/delete
++++if+(!string.length)
++++{
++++++++//+Backspace+detected,+allow+text+change,+no+need+to+process+the+text+any+further
++++++++return+YES;
++++}

++++//+Input+Validation
++++//+Prevent+invalid+character+input,+if+keyboard+is+numberpad
++++if+(textField.keyboardType+==+UIKeyboardTypeNumberPad)
++++{
++++++++if+([string+rangeOfCharacterFromSet:[NSCharacterSet+decimalDigitCharacterSet].invertedSet].location+!=+NSNotFound)
++++++++{
++++++++++++[self+presentAlert:+@"This+field+accepts+only+numeric+entries."];
++++++++++++return+NO;
++++++++}
++++}

++++//+Length+Validation
++++NSString+*proposedText+=+[textField.text+stringByReplacingCharactersInRange:range+withString:string];

++++//+Check+proposed+text+length+does+not+exceed+max+character+count
++++if+(proposedText.length+>+maxCharacters)
++++{
++++++++//+Present+alert+if+pasting+text
++++++++//+easy:+pasted+data+has+a+length+greater+than+1;+who+copy/pastes+one+character?
++++++++if+(string.length+>+1)
++++++++{
++++++++++++//+Pasting+text,+present+alert+so+the+user+knows+what+went+wrong
++++++++++++[self+presentAlert:+@"Paste+failed:+Maximum+character+count+exceeded."];
++++++++}

++++++++//+Character+count+exceeded,+disallow+text+change
++++++++return+NO;
++++}

++++//+Only+enable+the+OK/submit+button+if+they+have+entered+all+numbers+for+the+last+four
++++//+of+their+SSN+(prevents+early+submissions/trips+to+authentication+server,+etc)
++++self.answerButton.enabled+=+(proposedText.length+==+maxCharacters);

++++//+Allow+text+change
++++return+YES;
}|237370|entityMap^0|19|2|0|0|B|S|1P|H|2B|B|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|17|8|@]|D|@]|E|$]]|$1|L|3|M|5|N|7|18|8|@]|D|@]|E|$O|P]]|$1|Q|3|R|5|6|7|19|8|@]|D|@]|E|$]]|$1|S|3|T|5|N|7|1A|8|@]|D|@]|E|$O|P]]|$1|U|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|V|$]]

This is how you might handle the problem on a SSN verification field, you can modify the max length and remove the <code>if</code> statement checking for keyboard type if you need to.

There is also logic to suppress the max length alerts when the user is typing as opposed to pasting data.

Within the context of this code, <code>presentAlert()/presentAlert:</code> is just some basic function that presents a <code>UIAlertController</code> (or a legacy <code>UIAlertView</code>) using the message string passed.

<h2>Swift 5</h2>

<pre><code>// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the 
// object that will contain this code, because otherwise it would never be called.
//
// There are also some better stylistic approaches in Swift to avoid all the 
// nested statements, but I wanted to keep the styles similar to allow others 
// to contrast and compare between the two languages a little easier.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool {

 // Handle backspace/delete
 guard !string.isEmpty else {

 // Backspace detected, allow text change, no need to process the text any further
 return true
 }

 // Input Validation
 // Prevent invalid character input, if keyboard is numberpad
 if textField.keyboardType == .numberPad {

 // Check for invalid input characters
 if CharacterSet(charactersIn: "0123456789").isSuperset(of: CharacterSet(charactersIn: string)) {

 // Present alert so the user knows what went wrong
 presentAlert("This field accepts only numeric entries.")

 // Invalid characters detected, disallow text change
 return false
 }
 }

 // Length Processing
 // Need to convert the NSRange to a Swift-appropriate type
 if let text = textField.text, let range = Range(range, in: text) {

 let proposedText = text.replacingCharacters(in: range, with: string)

 // Check proposed text length does not exceed max character count
 guard proposedText.count &lt;= maxCharacters else {

 // Present alert if pasting text
 // easy: pasted data has a length greater than 1; who copy/pastes one character?
 if string.count &gt; 1 {

 // Pasting text, present alert so the user knows what went wrong
 presentAlert("Paste failed: Maximum character count exceeded.")
 }

 // Character count exceeded, disallow text change
 return false
 }

 // Only enable the OK/submit button if they have entered all numbers for the last four
 // of their SSN (prevents early submissions/trips to authentication server, etc)
 answerButton.isEnabled = (proposedText.count == 4)
 }

 // Allow text change
 return true
}
</code></pre>

<h2>Objective-C</h2>

<pre><code>// NOTE: This code assumes you have set the UITextField(s)'s delegate property to the 
// object that will contain this code, because otherwise it would never be called.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
 // Handle backspace/delete
 if (!string.length)
 {
 // Backspace detected, allow text change, no need to process the text any further
 return YES;
 }

 // Input Validation
 // Prevent invalid character input, if keyboard is numberpad
 if (textField.keyboardType == UIKeyboardTypeNumberPad)
 {
 if ([string rangeOfCharacterFromSet:[NSCharacterSet decimalDigitCharacterSet].invertedSet].location != NSNotFound)
 {
 [self presentAlert: @"This field accepts only numeric entries."];
 return NO;
 }
 }

 // Length Validation
 NSString *proposedText = [textField.text stringByReplacingCharactersInRange:range withString:string];

 // Check proposed text length does not exceed max character count
 if (proposedText.length &gt; maxCharacters)
 {
 // Present alert if pasting text
 // easy: pasted data has a length greater than 1; who copy/pastes one character?
 if (string.length &gt; 1)
 {
 // Pasting text, present alert so the user knows what went wrong
 [self presentAlert: @"Paste failed: Maximum character count exceeded."];
 }

 // Character count exceeded, disallow text change
 return NO;
 }

 // Only enable the OK/submit button if they have entered all numbers for the last four
 // of their SSN (prevents early submissions/trips to authentication server, etc)
 self.answerButton.enabled = (proposedText.length == maxCharacters);

 // Allow text change
 return YES;
}
</code></pre>

blocks|key|237406|text|您可以使用此代码在textField中仅允许数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|237407|在为textField设置委托之前|237408|++++++textFieldName.delegate=self;|code-block|syntax|javascript|237409|或|237410|++++++[textFieldName+setDelegate:self];|237411|然后使用此代码仅允许数字到textField|237412|++++++-+(BOOL)+textField:+(UITextField+*)theTextField+shouldChangeCharactersInRange:(NSRange)range+replacementString:+(NSString+*)string+{
//return+yes+or+no+after+comparing+the+characters

++++++//+allow+backspace
++++++if+(!string.length)
++++++{
+++++++++++return+YES;
++++++}

++++++////for+Decimal+value+start//////This+code+use+use+for+allowing+single+decimal+value
++++++//++++if+([theTextField.text+rangeOfString:@"."].location+==+NSNotFound)
++++++//++++{
++++++//++++++++if+([string+isEqualToString:@"."])+{
++++++//++++++++++++return+YES;
++++++//++++++++}
++++++//++++}
++++++//++++else
++++++//++++{
++++++//++++++++if+([[theTextField.text+substringFromIndex:[theTextField.text+rangeOfString:@"."].location]+length]>2)+++//+this+allow+2+digit+after+decimal+
++++++//++++++++{
++++++//++++++++++++return+NO;
++++++//++++++++}
++++++//++++}
++++++////for+Decimal+value+End//////This+code+use+use+for+allowing+single+decimal+value

++++++//+allow+digit+0+to+9
++++++if+([string+intValue])
++++++{
++++++++++++return+YES;
++++++}

++++++return+NO;
++++}|237413|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

You can use this code to allow only number in textField.

Before that set delegate for textField

<pre><code> textFieldName.delegate=self;
</code></pre>

or

<pre><code> [textFieldName setDelegate:self];
</code></pre>

Than use this code to allow only digit to textField

<pre><code> - (BOOL) textField: (UITextField *)theTextField shouldChangeCharactersInRange:(NSRange)range replacementString: (NSString *)string {
//return yes or no after comparing the characters

 // allow backspace
 if (!string.length)
 {
 return YES;
 }

 ////for Decimal value start//////This code use use for allowing single decimal value
 // if ([theTextField.text rangeOfString:@"."].location == NSNotFound)
 // {
 // if ([string isEqualToString:@"."]) {
 // return YES;
 // }
 // }
 // else
 // {
 // if ([[theTextField.text substringFromIndex:[theTextField.text rangeOfString:@"."].location] length]&gt;2) // this allow 2 digit after decimal 
 // {
 // return NO;
 // }
 // }
 ////for Decimal value End//////This code use use for allowing single decimal value

 // allow digit 0 to 9
 if ([string intValue])
 {
 return YES;
 }

 return NO;
 }
</code></pre>

blocks|key|455576|text|我用了这个，它起作用了！！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455577|-(BOOL)textField:(UITextField+*)textField+shouldChangeCharactersInRange:(NSRange)range+replacementString:(NSString+*)string{
++++//+Check+for+non-numeric+characters
++++NSUInteger+lengthOfString+=+string.length;
++++for+(NSInteger+index+=+0;+index+<+lengthOfString;+index%2B%2B)+{
++++++++unichar+character+=+[string+characterAtIndex:index];
++++++++if+(character+<+48)+return+NO;+//+48+unichar+for+0
++++++++if+(character+>+57)+return+NO;+//+57+unichar+for+9
++++}
++++//+Check+total+length+for+restrict+user
++++NSUInteger+proposedNewLength+=+textField.text.length+-+range.length+%2B+string.length;
++++if+(proposedNewLength+>+6)
++++++++return+YES;
++++return+YES;+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
}|code-block|syntax|javascript|455578|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I applied this and it works!!
<pre><code>-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
 // Check for non-numeric characters
 NSUInteger lengthOfString = string.length;
 for (NSInteger index = 0; index &lt; lengthOfString; index++) {
 unichar character = [string characterAtIndex:index];
 if (character &lt; 48) return NO; // 48 unichar for 0
 if (character &gt; 57) return NO; // 57 unichar for 9
 }
 // Check total length for restrict user
 NSUInteger proposedNewLength = textField.text.length - range.length + string.length;
 if (proposedNewLength &gt; 6)
 return YES;
 return YES; 
}
</code></pre>

blocks|key|455602|text|-+(BOOL)+textField:+(UITextField+*)textField+shouldChangeCharactersInRange:(NSRange)range+replacementString:+(NSString+*)string+{

++++NSNumberFormatter+*+nf+=+[[NSNumberFormatter+alloc]+init];
++++[nf+setNumberStyle:NSNumberFormatterNoStyle];

++++NSString+*+newString+=+[NSString+stringWithFormat:@"%25@%25@",textField.text,string];
++++NSNumber+*+number+=+[nf+numberFromString:newString];

++++if+(number)
++++++++return+YES;
++++else
+++++++return+NO;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|455603|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>- (BOOL) textField: (UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString: (NSString *)string {

 NSNumberFormatter * nf = [[NSNumberFormatter alloc] init];
 [nf setNumberStyle:NSNumberFormatterNoStyle];

 NSString * newString = [NSString stringWithFormat:@"%@%@",textField.text,string];
 NSNumber * number = [nf numberFromString:newString];

 if (number)
 return YES;
 else
 return NO;
}
</code></pre>

blocks|key|238496|text|保持不同的演示数据与内部表示。有一种更简单的方法。让NSNumberFormatter来完成这项工作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|238497|+NSNumberFormatter*+ns+=+[[NSNumberFormatter+alloc]+init];
+ns.numberStyle+=+NSNumberFormatterDecimalStyle;
+[ns+setMaximumFractionDigits:2];
+//+This+is+your+internal+representation+of+the+localized+number
+double+a+=+[[ns+numberFromString:self.textIVA.text]+doubleValue]];

[mylabel+setText:[NSString+stringWithFormat:@"€+%25@",
+++++[NSNumberFormatter+localizedStringFromNumber:
++++++++++++++++++++++++++[NSNumber+numberWithDouble:a]
++++++++++++++++++++++++++++++++++++++numberStyle:NSNumberFormatterDecimalStyle]]];|code-block|syntax|javascript|238498|entityMap^0|Q|H|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Keep distinct presentation data from internal representation. There is a simpler way. Let <code>NSNumberFormatter</code> do the job:

<pre><code> NSNumberFormatter* ns = [[NSNumberFormatter alloc] init];
 ns.numberStyle = NSNumberFormatterDecimalStyle;
 [ns setMaximumFractionDigits:2];
 // This is your internal representation of the localized number
 double a = [[ns numberFromString:self.textIVA.text] doubleValue]];

[mylabel setText:[NSString stringWithFormat:@"€ %@",
 [NSNumberFormatter localizedStringFromNumber:
 [NSNumber numberWithDouble:a]
 numberStyle:NSNumberFormatterDecimalStyle]]];
</code></pre>

blocks|key|455717|text|我已经修改了@iDev的答案，使其适用于数字和"."：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455718|-(BOOL)textField:(UITextField+*)textField+shouldChangeCharactersInRange:(NSRange)range+replacementString:(NSString+*)string{
+++++//+Check+for+non-numeric+characters
+++++NSUInteger+lengthOfString+=+string.length;
+++++for+(NSInteger+index+=+0;+index+<+lengthOfString;+index%2B%2B)+{
+++++++++unichar+character+=+[string+characterAtIndex:index];
+++++++++if+((character+<+48)+&&+(character+!=+46))+return+NO;+
+++++++++//+48+unichar+for+0,+and+46+unichar+for+point
+++++++++if+(character+>+57)+return+NO;+
+++++++++//+57+unichar+for+9
+++++}
+++++//+Check+for+total+length
+++++NSUInteger+proposedNewLength+=+textField.text.length+-+range.length+%2B+string.length;
+++++if+(proposedNewLength+>+6)
+++++++++return+YES;
+++++return+YES;+
+}|code-block|syntax|javascript|455719|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I have modified @iDev's answer to work for digitals and ".":

<pre><code>-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
 // Check for non-numeric characters
 NSUInteger lengthOfString = string.length;
 for (NSInteger index = 0; index &lt; lengthOfString; index++) {
 unichar character = [string characterAtIndex:index];
 if ((character &lt; 48) &amp;&amp; (character != 46)) return NO; 
 // 48 unichar for 0, and 46 unichar for point
 if (character &gt; 57) return NO; 
 // 57 unichar for 9
 }
 // Check for total length
 NSUInteger proposedNewLength = textField.text.length - range.length + string.length;
 if (proposedNewLength &gt; 6)
 return YES;
 return YES; 
 }
</code></pre>

blocks|key|238581|text|NSString*+val+=+[[textField+text]+stringByReplacingCharactersInRange:range+withString:string];
++++NSCharacterSet+*allowedCharacterSet+=+[NSCharacterSet+decimalDigitCharacterSet];
++++if+([[string+componentsSeparatedByCharactersInSet:[allowedCharacterSet+invertedSet]]+count]+>+1+%7C%7C+[val+length]+>+5)+{
++++++++return+NO;
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|238582|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>NSString* val = [[textField text] stringByReplacingCharactersInRange:range withString:string];
 NSCharacterSet *allowedCharacterSet = [NSCharacterSet decimalDigitCharacterSet];
 if ([[string componentsSeparatedByCharactersInSet:[allowedCharacterSet invertedSet]] count] &gt; 1 || [val length] &gt; 5) {
 return NO;
 }
</code></pre>

blocks|key|455755|text|如果您使用我的specification+pattern，则代码如下所示|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|455756|textField.delegate+=+self

lazy+var+specification:+Specification+=+{
++++return+RegularExpressionSpecification(pattern:+"%5E(%7C0%7C[1-9]\\d{0,6})$")
}()

func+textField(textField:+UITextField,+shouldChangeCharactersInRange+range:+NSRange,+replacementString+string:+String)+->+Bool+{
++++let+textFieldString:+NSString+=+textField.text+??+""
++++let+s+=+textFieldString.stringByReplacingCharactersInRange(range,+withString:string)
++++return+specification.isSatisfiedBy(s)
}

func+textFieldShouldReturn(textField:+UITextField)+->+Bool+{
++++let+s+=+textField.text+??+""
++++let+isTextValid+=+specification.isSatisfiedBy(s)
++++if+isTextValid+{
++++++++textField.resignFirstResponder()
++++}
++++return+false
}|code-block|syntax|javascript|455757|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/neoneye/SpecificationPattern^0|7|L|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

If you use my <a href="https://github.com/neoneye/SpecificationPattern" rel="nofollow">specification pattern</a> then code looks like this

<pre><code>textField.delegate = self

lazy var specification: Specification = {
 return RegularExpressionSpecification(pattern: "^(|0|[1-9]\\d{0,6})$")
}()

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -&gt; Bool {
 let textFieldString: NSString = textField.text ?? ""
 let s = textFieldString.stringByReplacingCharactersInRange(range, withString:string)
 return specification.isSatisfiedBy(s)
}

func textFieldShouldReturn(textField: UITextField) -&gt; Bool {
 let s = textField.text ?? ""
 let isTextValid = specification.isSatisfiedBy(s)
 if isTextValid {
 textField.resignFirstResponder()
 }
 return false
}
</code></pre>

blocks|key|238635|text|Works+fine+for+me+:

-+(BOOL)textField:(UITextField+*)textField+shouldChangeCharactersInRange:(NSRange)range+replacementString:(NSString+*)string+{
if+(([string+rangeOfCharacterFromSet:[[NSCharacterSet+decimalDigitCharacterSet]+invertedSet]].location+!=+NSNotFound)+&&+!(range.length==1+&&+string.length==0))+{
++++++++++++return+NO;
++++++++}
++++++++return+YES;
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|238636|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>Works fine for me :

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
if (([string rangeOfCharacterFromSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].location != NSNotFound) &amp;&amp; !(range.length==1 &amp;&amp; string.length==0)) {
 return NO;
 }
 return YES;
 }
</code></pre>

blocks|key|455785|text|使用以下代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455786|NSString*+val+=+[[textField+text]+stringByReplacingCharactersInRange:range+withString:string];
NSCharacterSet+*allowedCharacterSet+=+[NSCharacterSet+decimalDigitCharacterSet];
if+([[string+componentsSeparatedByCharactersInSet:[allowedCharacterSet+invertedSet]]+count]+>+1+%7C%7C+[val+length]+>+5)+{
++++return+NO;
}|code-block|syntax|javascript|455787|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Use this code:

<pre><code>NSString* val = [[textField text] stringByReplacingCharactersInRange:range withString:string];
NSCharacterSet *allowedCharacterSet = [NSCharacterSet decimalDigitCharacterSet];
if ([[string componentsSeparatedByCharactersInSet:[allowedCharacterSet invertedSet]] count] &gt; 1 || [val length] &gt; 5) {
 return NO;
}
</code></pre>

blocks|key|455792|text|swift+3|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455793|func+textField(_+textField:+UITextField,+shouldChangeCharactersIn+range:+NSRange,+replacementString+string:+String)+->+Bool+{
++++if+textField==yourTextFieldOutlet+{
++++++++++++++++if(CharacterSet.decimalDigits.isSuperset(of:+CharacterSet(charactersIn:+yourTextFieldOutlet.text!))){
//if+numbers+only,+then+your+code+here
++++++++++++++++}
++++++++++++++++else{
++++++++++++++++showAlert(title:+"Error",message:+"Enter+Number+only",type:+"failure")
++++++++++++++++}
++++++++++++}
++++return+true
++++}|code-block|syntax|javascript|455794|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

swift 3

<pre><code>func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool {
 if textField==yourTextFieldOutlet {
 if(CharacterSet.decimalDigits.isSuperset(of: CharacterSet(charactersIn: yourTextFieldOutlet.text!))){
//if numbers only, then your code here
 }
 else{
 showAlert(title: "Error",message: "Enter Number only",type: "failure")
 }
 }
 return true
 }
</code></pre>

blocks|key|455799|text|在Swift中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455800|++++func+textField(_+textField:+UITextField,+shouldChangeCharactersIn+range:+NSRange,+replacementString+string:+String)+->+Bool+{
++++++++return+string.isEmpty+%7C%7C+Int(string)+!=+nil
++++}|code-block|syntax|javascript|455801|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In Swift:

<pre class="lang-swift prettyprint-override"><code> func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool {
 return string.isEmpty || Int(string) != nil
 }
</code></pre>

blocks|key|455856|text|swift+5|type|unstyled|depth|inlineStyleRanges|entityRanges|data|455857|++++//MARK:-+UITextFieldDelegate

func+textField(_+textField:+UITextField,+shouldChangeCharactersIn+range:+NSRange,+replacementString+string:+String)+->+Bool+{

++++let+allowedCharacters+=+"1234567890"
++++let+allowedCharcterSet+=+CharacterSet(charactersIn:+allowedCharacters)
++++let+typedCharcterSet+=+CharacterSet(charactersIn:+string)
++++return+allowedCharcterSet.isSuperset(of:+typedCharcterSet)
}|code-block|syntax|javascript|455858|现在只需点击1234567890即可|455859|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

swift 5

<pre><code> //MARK:- UITextFieldDelegate

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -&gt; Bool {

 let allowedCharacters = "1234567890"
 let allowedCharcterSet = CharacterSet(charactersIn: allowedCharacters)
 let typedCharcterSet = CharacterSet(charactersIn: string)
 return allowedCharcterSet.isSuperset(of: typedCharcterSet)
}
</code></pre>

You can now just tap 1234567890 only

The iPad does not have a "Numpad" keyboard like the iPhone/iPod does.

I'm looking to find how I can restrict the user's keyboard to only accept values 0 through 9.

I would imagine using UITextField's "shouldChangeCharactersInRange" but I don't know the best way to implement it.

Allow only Numbers for UITextField input

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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iPad没有像iPhone/iPod那样的“数字键盘”。我想知道如何限制用户的键盘只接受从0到9的值。我可以想象使用UITextField的"shouldChangeCharactersInRange“，但我不知道实现它的最佳方式。

问只允许UITextField输入数字
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问只允许UITextField输入数字EN