格式化UITextField以进行信用卡输入,如(xxxx xxxx xxxx xxxx)

Question

我想格式化UITextField输入信用卡号码,使其只允许输入数字并自动插入空格,以便数字的格式如下:

XXXX XXXX XXXX XXXX

我怎样才能做到这一点？

Answer 1

如果您正在使用Swift,请阅读我对Swift 4的答案的端口并使用它.

如果你在Objective-C ...

首先,给你UITextFieldDelegate,添加这些实例变量......

NSString *previousTextFieldContent;
UITextRange *previousSelection;

......以及这些方法:

// Version 1.3
// Source and explanation: http://stackoverflow.com/a/19161529/1709587
-(void)reformatAsCardNumber:(UITextField *)textField
{
    // In order to make the cursor end up positioned correctly, we need to
    // explicitly reposition it after we inject spaces into the text.
    // targetCursorPosition keeps track of where the cursor needs to end up as
    // we modify the string, and at the end we set the cursor position to it.
    NSUInteger targetCursorPosition = 
        [textField offsetFromPosition:textField.beginningOfDocument
                           toPosition:textField.selectedTextRange.start];

    NSString *cardNumberWithoutSpaces = 
        [self removeNonDigits:textField.text
                  andPreserveCursorPosition:&targetCursorPosition];

    if ([cardNumberWithoutSpaces length] > 19) {
        // If the user is trying to enter more than 19 digits, we prevent 
        // their change, leaving the text field in  its previous state.
        // While 16 digits is usual, credit card numbers have a hard 
        // maximum of 19 digits defined by ISO standard 7812-1 in section
        // 3.8 and elsewhere. Applying this hard maximum here rather than
        // a maximum of 16 ensures that users with unusual card numbers
        // will still be able to enter their card number even if the
        // resultant formatting is odd.
        [textField setText:previousTextFieldContent];
        textField.selectedTextRange = previousSelection;
        return;
    }

    NSString *cardNumberWithSpaces = 
        [self insertCreditCardSpaces:cardNumberWithoutSpaces
           andPreserveCursorPosition:&targetCursorPosition];

    textField.text = cardNumberWithSpaces;
    UITextPosition *targetPosition = 
        [textField positionFromPosition:[textField beginningOfDocument]
                                 offset:targetCursorPosition];

    [textField setSelectedTextRange:
        [textField textRangeFromPosition:targetPosition
                              toPosition:targetPosition]
    ];
}

-(BOOL)textField:(UITextField *)textField 
         shouldChangeCharactersInRange:(NSRange)range 
                     replacementString:(NSString *)string
{
    // Note textField's current state before performing the change, in case
    // reformatTextField wants to revert it
    previousTextFieldContent = textField.text;
    previousSelection = textField.selectedTextRange;

    return YES;
}

/*
 Removes non-digits from the string, decrementing `cursorPosition` as
 appropriate so that, for instance, if we pass in `@"1111 1123 1111"`
 and a cursor position of `8`, the cursor position will be changed to
 `7` (keeping it between the '2' and the '3' after the spaces are removed).
 */
- (NSString *)removeNonDigits:(NSString *)string
                andPreserveCursorPosition:(NSUInteger *)cursorPosition 
{
    NSUInteger originalCursorPosition = *cursorPosition;
    NSMutableString *digitsOnlyString = [NSMutableString new];
    for (NSUInteger i=0; i<[string length]; i++) {
        unichar characterToAdd = [string characterAtIndex:i];
        if (isdigit(characterToAdd)) {
            NSString *stringToAdd = 
                [NSString stringWithCharacters:&characterToAdd
                                        length:1];

            [digitsOnlyString appendString:stringToAdd];
        }
        else {
            if (i < originalCursorPosition) {
                (*cursorPosition)--;
            }
        }
    }

    return digitsOnlyString;
}

/*
 Detects the card number format from the prefix, then inserts spaces into
 the string to format it as a credit card number, incrementing `cursorPosition`
 as appropriate so that, for instance, if we pass in `@"111111231111"` and a
 cursor position of `7`, the cursor position will be changed to `8` (keeping
 it between the '2' and the '3' after the spaces are added).
 */
- (NSString *)insertCreditCardSpaces:(NSString *)string
                          andPreserveCursorPosition:(NSUInteger *)cursorPosition
{
    // Mapping of card prefix to pattern is taken from
    // https://baymard.com/checkout-usability/credit-card-patterns

    // UATP cards have 4-5-6 (XXXX-XXXXX-XXXXXX) format
    bool is456 = [string hasPrefix: @"1"];

    // These prefixes reliably indicate either a 4-6-5 or 4-6-4 card. We treat all
    // these as 4-6-5-4 to err on the side of always letting the user type more
    // digits.
    bool is465 = [string hasPrefix: @"34"] ||
                 [string hasPrefix: @"37"] ||

                 // Diners Club
                 [string hasPrefix: @"300"] ||
                 [string hasPrefix: @"301"] ||
                 [string hasPrefix: @"302"] ||
                 [string hasPrefix: @"303"] ||
                 [string hasPrefix: @"304"] ||
                 [string hasPrefix: @"305"] ||
                 [string hasPrefix: @"309"] ||
                 [string hasPrefix: @"36"] ||
                 [string hasPrefix: @"38"] ||
                 [string hasPrefix: @"39"];

    // In all other cases, assume 4-4-4-4-3.
    // This won't always be correct; for instance, Maestro has 4-4-5 cards
    // according to https://baymard.com/checkout-usability/credit-card-patterns,
    // but I don't know what prefixes identify particular formats.
    bool is4444 = !(is456 || is465);

    NSMutableString *stringWithAddedSpaces = [NSMutableString new];
    NSUInteger cursorPositionInSpacelessString = *cursorPosition;
    for (NSUInteger i=0; i<[string length]; i++) {
        bool needs465Spacing = (is465 && (i == 4 || i == 10 || i == 15));
        bool needs456Spacing = (is456 && (i == 4 || i == 9 || i == 15));
        bool needs4444Spacing = (is4444 && i > 0 && (i % 4) == 0);

        if (needs465Spacing || needs456Spacing || needs4444Spacing) {
            [stringWithAddedSpaces appendString:@" "];
            if (i < cursorPositionInSpacelessString) {
                (*cursorPosition)++;
            }
        }
        unichar characterToAdd = [string characterAtIndex:i];
        NSString *stringToAdd =
        [NSString stringWithCharacters:&characterToAdd length:1];

        [stringWithAddedSpaces appendString:stringToAdd];
    }

    return stringWithAddedSpaces;
}

其次,reformatCardNumber:只要文本字段触发UIControlEventEditingChanged事件,就设置为调用:

[yourTextField addTarget:yourTextFieldDelegate 
                             action:@selector(reformatAsCardNumber:)
                   forControlEvents:UIControlEventEditingChanged];

(当然,您需要在文本字段及其委托实例化之后的某个时刻执行此操作.如果您使用的是故事板,则viewDidLoad视图控制器的方法是合适的位置.

一些解释

这是一个看似复杂的问题.可能不会立即明显的三个重要问题(以及之前的答案都没有考虑到):

1. 虽然XXXX XXXX XXXX XXXX信用卡和借记卡号码的格式是最常见的格式,但它并不是唯一的格式.例如,美国运通卡通常以15位数字XXXX XXXXXX XXXXX格式编写,如下所示:

   

   即使Visa卡也可以少于 16位,Maestro卡可以有更多:

   

2. 用户可以使用更多方式与文本字段进行交互,而不仅仅是在现有输入的末尾键入单个字符.您还必须正确处理用户在字符串中间添加字符,删除单个字符,删除多个选定字符以及粘贴多个字符.对此问题采用一些更简单/更天真的方法将无法正确处理其中一些交互.最常见的情况是用户在字符串中间粘贴多个字符以替换其他字符,这个解决方案通常足以处理它.

3. 您不仅需要在用户修改后正确地重新格式化文本字段的文本 - 您还需要明智地定位文本光标.对于没有考虑到这一点的问题,天真的方法几乎肯定会在某些情况下使用文本光标做一些愚蠢的事情(比如在用户在其中间添加一个数字后将其放到文本字段的末尾) ).

为了解决问题#1,我们使用卡号前缀的部分映射到Baymard Institute策划的格式,网址为https://baymard.com/checkout-usability/credit-card-patterns.我们可以从前几位数字自动检测卡提供商,并(在某些情况下)推断格式并相应地调整我们的格式.感谢cnotethegr8为这个答案贡献了这个想法.

处理问题#2(以及上面代码中使用的方式)的最简单和最简单的方法是去掉所有空格,并在每次文本字段的内容发生变化时将它们重新插入正确的位置,从而使我们无需计算是什么样的文本操作(插入,删除或替换)正在进行并以不同的方式处理可能性.

为了处理问题#3,我们跟踪光标的所需索引如何随着我们去掉非数字然后插入空格而改变.这就是为什么代码使用NSMutableString而不是使用NSString字符串替换方法而非冗长地执行这些操作的原因.

最后,还有一个潜伏的陷阱:当用户在文本字段中选择文本时,NO从textField: shouldChangeCharactersInRange: replacementString休息处返回"剪切"按钮,这就是我不这样做的原因.NO从该方法返回导致'Cut'根本不更新剪贴板,我知道没有修复或解决方法.因此,我们需要在UIControlEventEditingChanged处理程序中重新格式化文本字段,而不是(更明显地)shouldChangeCharactersInRange:本身.

幸运的是,UIControl事件处理程序似乎在UI更新刷新到屏幕之前被调用,因此这种方法很好.

还有一大堆关于文本字段应该表现得如何没有明显正确答案的小问题:

• 如果用户试图粘贴会导致文本字段内容超过19位的内容,则应插入粘贴字符串的开头(直到达到19位数)并且其余部分被裁剪,或者根本不应该插入任何内容？
• 如果用户尝试通过将光标定位在其后并按退格键来删除单个空格,则应该没有任何反应并且光标保持在原位,如果光标向左移动一个字符(将其放置在空格之前),或者应该删除空格左侧的数字,就好像光标已经留在空间中一样？
• 当用户键入第四,第八或第十二位时,是否应立即插入空格并在其后移动光标,或者在用户键入第五,第九或第十三位后是否应插入空格？
• 当用户删除空格后的第一个数字时,如果这不会导致空间被完全删除,那么这是否会导致其光标位于空格之前或之后？

可能任何这些问题的答案都是足够的,但我列出它们只是为了表明实际上有许多特殊情况你可能想在这里仔细思考,如果你足够痴迷.在上面的代码中,我已经选择了对我来说似乎合理的这些问题的答案.如果您对这些与我的代码行为方式不兼容的要点有强烈的感受,那么应该很容易根据您的需要进行调整.

Answer 2

您可以优化我的代码,或者可能有一种更简单的方法,但这段代码应该有效:

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    __block NSString *text = [textField text];

    NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789\b"];
    string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];
    if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {
        return NO;
    }

    text = [text stringByReplacingCharactersInRange:range withString:string];
    text = [text stringByReplacingOccurrencesOfString:@" " withString:@""];

    NSString *newString = @"";
    while (text.length > 0) {
        NSString *subString = [text substringToIndex:MIN(text.length, 4)];
        newString = [newString stringByAppendingString:subString];
        if (subString.length == 4) {
            newString = [newString stringByAppendingString:@" "];
        }
        text = [text substringFromIndex:MIN(text.length, 4)];
    }

    newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];

    if (newString.length >= 20) {
        return NO;
    }

    [textField setText:newString];

    return NO;
}

Answer 3

下面是一个工作的Swift 4端口Logicopolis的答案(这是我在Objective-C中接受的旧版本的Swift 2端口)增强了cnotethegr8 支持Amex卡的技巧,然后进一步增强以支持更多卡格式.如果您还没有,我建议查看已接受的答案,因为它有助于解释许多此代码背后的动机.

请注意,查看此操作所需的最小步骤系列是:

1. 在Swift中创建一个新的单一视图应用程序.
2. 在Main.storyboard,添加文本字段.
3. 创建文本字段ViewController的委托.
4. 将下面的代码粘贴到ViewController.swift.
5. 连接IBOutlet到文本字段.
6. 运行您的应用程序并在文本字段中键入.

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {
    private var previousTextFieldContent: String?
    private var previousSelection: UITextRange?
    @IBOutlet var yourTextField: UITextField!;

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib
        yourTextField.addTarget(self, action: #selector(reformatAsCardNumber), for: .editingChanged)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        previousTextFieldContent = textField.text;
        previousSelection = textField.selectedTextRange;
        return true
    }

    @objc func reformatAsCardNumber(textField: UITextField) {
        var targetCursorPosition = 0
        if let startPosition = textField.selectedTextRange?.start {
            targetCursorPosition = textField.offset(from: textField.beginningOfDocument, to: startPosition)
        }

        var cardNumberWithoutSpaces = ""
        if let text = textField.text {
            cardNumberWithoutSpaces = self.removeNonDigits(string: text, andPreserveCursorPosition: &targetCursorPosition)
        }

        if cardNumberWithoutSpaces.count > 19 {
            textField.text = previousTextFieldContent
            textField.selectedTextRange = previousSelection
            return
        }

        let cardNumberWithSpaces = self.insertCreditCardSpaces(cardNumberWithoutSpaces, preserveCursorPosition: &targetCursorPosition)
        textField.text = cardNumberWithSpaces

        if let targetPosition = textField.position(from: textField.beginningOfDocument, offset: targetCursorPosition) {
            textField.selectedTextRange = textField.textRange(from: targetPosition, to: targetPosition)
        }
    }

    func removeNonDigits(string: String, andPreserveCursorPosition cursorPosition: inout Int) -> String {
        var digitsOnlyString = ""
        let originalCursorPosition = cursorPosition

        for i in Swift.stride(from: 0, to: string.count, by: 1) {
            let characterToAdd = string[string.index(string.startIndex, offsetBy: i)]
            if characterToAdd >= "0" && characterToAdd <= "9" {
                digitsOnlyString.append(characterToAdd)
            }
            else if i < originalCursorPosition {
                cursorPosition -= 1
            }
        }

        return digitsOnlyString
    }

    func insertCreditCardSpaces(_ string: String, preserveCursorPosition cursorPosition: inout Int) -> String {
        // Mapping of card prefix to pattern is taken from
        // https://baymard.com/checkout-usability/credit-card-patterns

        // UATP cards have 4-5-6 (XXXX-XXXXX-XXXXXX) format
        let is456 = string.hasPrefix("1")

        // These prefixes reliably indicate either a 4-6-5 or 4-6-4 card. We treat all these
        // as 4-6-5-4 to err on the side of always letting the user type more digits.
        let is465 = [
            // Amex
            "34", "37",

            // Diners Club
            "300", "301", "302", "303", "304", "305", "309", "36", "38", "39"
        ].contains { string.hasPrefix($0) }

        // In all other cases, assume 4-4-4-4-3.
        // This won't always be correct; for instance, Maestro has 4-4-5 cards according
        // to https://baymard.com/checkout-usability/credit-card-patterns, but I don't
        // know what prefixes identify particular formats.
        let is4444 = !(is456 || is465)

        var stringWithAddedSpaces = ""
        let cursorPositionInSpacelessString = cursorPosition

        for i in 0..<string.count {
            let needs465Spacing = (is465 && (i == 4 || i == 10 || i == 15))
            let needs456Spacing = (is456 && (i == 4 || i == 9 || i == 15))
            let needs4444Spacing = (is4444 && i > 0 && (i % 4) == 0)

            if needs465Spacing || needs456Spacing || needs4444Spacing {
                stringWithAddedSpaces.append(" ")

                if i < cursorPositionInSpacelessString {
                    cursorPosition += 1
                }
            }

            let characterToAdd = string[string.index(string.startIndex, offsetBy:i)]
            stringWithAddedSpaces.append(characterToAdd)
        }

        return stringWithAddedSpaces
    }
}

适应其他情况 - 比如你的代表不是ViewController- 被留给读者练习.

Answer 4

我觉得这个很好:

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
    {

        NSLog(@"%@",NSStringFromRange(range));

        // Only the 16 digits + 3 spaces
        if (range.location == 19) {
            return NO;
        }

        // Backspace
        if ([string length] == 0)
            return YES;

        if ((range.location == 4) || (range.location == 9) || (range.location == 14))
        {

            NSString *str    = [NSString stringWithFormat:@"%@ ",textField.text];
            textField.text   = str;
        }

        return YES;
    }

Answer 5

使用Fawkes答案的Swift 3解决方案作为基础.添加了Amex卡格式支持.卡类型更改时添加了重组.

首先使用以下代码创建新类:

extension String {

    func containsOnlyDigits() -> Bool
    {

        let notDigits = NSCharacterSet.decimalDigits.inverted

        if rangeOfCharacter(from: notDigits, options: String.CompareOptions.literal, range: nil) == nil
        {
            return true
        }

        return false
    }
}
import UIKit

var creditCardFormatter : CreditCardFormatter
{
    return CreditCardFormatter.sharedInstance
}

class CreditCardFormatter : NSObject
{
    static let sharedInstance : CreditCardFormatter = CreditCardFormatter()

    func formatToCreditCardNumber(isAmex: Bool, textField : UITextField, withPreviousTextContent previousTextContent : String?, andPreviousCursorPosition previousCursorSelection : UITextRange?) {
        var selectedRangeStart = textField.endOfDocument
        if textField.selectedTextRange?.start != nil {
            selectedRangeStart = (textField.selectedTextRange?.start)!
        }
        if  let textFieldText = textField.text
        {
            var targetCursorPosition : UInt = UInt(textField.offset(from:textField.beginningOfDocument, to: selectedRangeStart))
            let cardNumberWithoutSpaces : String = removeNonDigitsFromString(string: textFieldText, andPreserveCursorPosition: &targetCursorPosition)
            if cardNumberWithoutSpaces.characters.count > 19
            {
                textField.text = previousTextContent
                textField.selectedTextRange = previousCursorSelection
                return
            }
            var cardNumberWithSpaces = ""
            if isAmex {
                cardNumberWithSpaces = insertSpacesInAmexFormat(string: cardNumberWithoutSpaces, andPreserveCursorPosition: &targetCursorPosition)
            }
            else
            {
                cardNumberWithSpaces = insertSpacesIntoEvery4DigitsIntoString(string: cardNumberWithoutSpaces, andPreserveCursorPosition: &targetCursorPosition)
            }
            textField.text = cardNumberWithSpaces
            if let finalCursorPosition = textField.position(from:textField.beginningOfDocument, offset: Int(targetCursorPosition))
            {
                textField.selectedTextRange = textField.textRange(from: finalCursorPosition, to: finalCursorPosition)
            }
        }
    }

    func removeNonDigitsFromString(string : String, andPreserveCursorPosition cursorPosition : inout UInt) -> String {
        var digitsOnlyString : String = ""
        for index in stride(from: 0, to: string.characters.count, by: 1)
        {
            let charToAdd : Character = Array(string.characters)[index]
            if isDigit(character: charToAdd)
            {
                digitsOnlyString.append(charToAdd)
            }
            else
            {
                if index < Int(cursorPosition)
                {
                    cursorPosition -= 1
                }
            }
        }
        return digitsOnlyString
    }

    private func isDigit(character : Character) -> Bool
    {
        return "\(character)".containsOnlyDigits()
    }

    func insertSpacesInAmexFormat(string : String, andPreserveCursorPosition cursorPosition : inout UInt) -> String {
        var stringWithAddedSpaces : String = ""
        for index in stride(from: 0, to: string.characters.count, by: 1)
        {
            if index == 4
            {
                stringWithAddedSpaces += " "
                if index < Int(cursorPosition)
                {
                    cursorPosition += 1
                }
            }
            if index == 10 {
                stringWithAddedSpaces += " "
                if index < Int(cursorPosition)
                {
                    cursorPosition += 1
                }
            }
            if index < 15 {
               let characterToAdd : Character = Array(string.characters)[index]
                stringWithAddedSpaces.append(characterToAdd)
            }
        }
        return stringWithAddedSpaces
    }


    func insertSpacesIntoEvery4DigitsIntoString(string : String, andPreserveCursorPosition cursorPosition : inout UInt) -> String {
        var stringWithAddedSpaces : String = ""
        for index in stride(from: 0, to: string.characters.count, by: 1)
        {
            if index != 0 && index % 4 == 0 && index < 16
            {
                stringWithAddedSpaces += " "

                if index < Int(cursorPosition)
                {
                    cursorPosition += 1
                }
            }
            if index < 16 {
                let characterToAdd : Character = Array(string.characters)[index]
                stringWithAddedSpaces.append(characterToAdd)
            }
        }
        return stringWithAddedSpaces
    }

}

在ViewControllerClass中添加此函数

func reformatAsCardNumber(textField:UITextField){
  let formatter = CreditCardFormatter()
  var isAmex = false
  if selectedCardType == "AMEX" {
    isAmex = true
    }
  formatter.formatToCreditCardNumber(isAmex: isAmex, textField: textField, withPreviousTextContent: textField.text, andPreviousCursorPosition: textField.selectedTextRange)
}

然后将target添加到textField

youtTextField.addTarget(self, action: #selector(self.reformatAsCardNumber(textField:)), for: UIControlEvents.editingChanged)

注册新变量并将卡片类型发送给它

var selectedCardType: String? {
  didSet{
    reformatAsCardNumber(textField: yourTextField)
  }
}

谢谢福克斯的代码!

Answer 6

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool
    {
        if textField == CardNumTxt
        {
            let replacementStringIsLegal = string.rangeOfCharacterFromSet(NSCharacterSet(charactersInString: "0123456789").invertedSet) == nil

            if !replacementStringIsLegal
            {
                return false
            }

            let newString = (textField.text! as NSString).stringByReplacingCharactersInRange(range, withString: string)
            let components = newString.componentsSeparatedByCharactersInSet(NSCharacterSet(charactersInString: "0123456789").invertedSet)

            let decimalString = components.joinWithSeparator("") as NSString
            let length = decimalString.length
            let hasLeadingOne = length > 0 && decimalString.characterAtIndex(0) == (1 as unichar)

            if length == 0 || (length > 16 && !hasLeadingOne) || length > 19
            {
                let newLength = (textField.text! as NSString).length + (string as NSString).length - range.length as Int

                return (newLength > 16) ? false : true
            }
            var index = 0 as Int
            let formattedString = NSMutableString()

            if hasLeadingOne
            {
                formattedString.appendString("1 ")
                index += 1
            }
            if length - index > 4
            {
                let prefix = decimalString.substringWithRange(NSMakeRange(index, 4))
                formattedString.appendFormat("%@-", prefix)
                index += 4
            }

            if length - index > 4
            {
                let prefix = decimalString.substringWithRange(NSMakeRange(index, 4))
                formattedString.appendFormat("%@-", prefix)
                index += 4
            }
            if length - index > 4
            {
                let prefix = decimalString.substringWithRange(NSMakeRange(index, 4))
                formattedString.appendFormat("%@-", prefix)
                index += 4
            }


            let remainder = decimalString.substringFromIndex(index)
            formattedString.appendString(remainder)
            textField.text = formattedString as String
            return false
        }
        else
        {
            return true
        }
    }

formattedString.appendFormat("%@ - ",前缀)chage of" - "您选择的任何其他

Answer 7

在 Swift 5 中：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if textField == cardNumberTextField {
            return formatCardNumber(textField: textField, shouldChangeCharactersInRange: range, replacementString: string)
        }
        return true
    }


    func formatCardNumber(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
        if textField == cardNumberTextField {
            let replacementStringIsLegal = string.rangeOfCharacter(from: NSCharacterSet(charactersIn: "0123456789").inverted) == nil

            if !replacementStringIsLegal {
                return false
            }

            let newString = (textField.text! as NSString).replacingCharacters(in: range, with: string)
            let components = newString.components(separatedBy: NSCharacterSet(charactersIn: "0123456789").inverted)
            let decimalString = components.joined(separator: "") as NSString
            let length = decimalString.length
            let hasLeadingOne = length > 0 && decimalString.character(at: 0) == (1 as unichar)

            if length == 0 || (length > 16 && !hasLeadingOne) || length > 19 {
                let newLength = (textField.text! as NSString).length + (string as NSString).length - range.length as Int

                return (newLength > 16) ? false : true
            }
            var index = 0 as Int
            let formattedString = NSMutableString()

            if hasLeadingOne {
                formattedString.append("1 ")
                index += 1
            }
            if length - index > 4 {
                let prefix = decimalString.substring(with: NSRange(location: index, length: 4))
                formattedString.appendFormat("%@ ", prefix)
                index += 4
            }

            if length - index > 4 {
                let prefix = decimalString.substring(with: NSRange(location: index, length: 4))
                formattedString.appendFormat("%@ ", prefix)
                index += 4
            }
            if length - index > 4 {
                let prefix = decimalString.substring(with: NSRange(location: index, length: 4))
                formattedString.appendFormat("%@ ", prefix)
                index += 4
            }

            let remainder = decimalString.substring(from: index)
            formattedString.append(remainder)
            textField.text = formattedString as String
            return false
        } else {
            return true
        }
    }

Answer 8

这是Mark Amery 接受的答案的Swift 5版本。

在您的类中添加这些变量：

@IBOutlet weak var cardNumberTextField: UITextField!
private var previousTextFieldContent: String?
private var previousSelection: UITextRange?

还要确保您的文本字段调用reformatAsCardNumber: from viewDidLoad():

cardNumberTextField.addTarget(self, action: #selector(reformatAsCardNumber), for: .editingChanged)

将其添加到您的UITextFieldDelegate：

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
   
    if textField == cardNumberTextField {
        previousTextFieldContent = textField.text;
        previousSelection = textField.selectedTextRange;
    }
    
    return true
}

最后在您的中包含以下方法viewController：

@objc func reformatAsCardNumber(textField: UITextField) {
    var targetCursorPosition = 0
    if let startPosition = textField.selectedTextRange?.start {
        targetCursorPosition = textField.offset(from: textField.beginningOfDocument, to: startPosition)
    }
    
    var cardNumberWithoutSpaces = ""
    if let text = textField.text {
        cardNumberWithoutSpaces = self.removeNonDigits(string: text, andPreserveCursorPosition: &targetCursorPosition)
    }
    
    if cardNumberWithoutSpaces.count > 19 {
        textField.text = previousTextFieldContent
        textField.selectedTextRange = previousSelection
        return
    }
    
    let cardNumberWithSpaces = self.insertSpacesEveryFourDigitsIntoString(string: cardNumberWithoutSpaces, andPreserveCursorPosition: &targetCursorPosition)
    textField.text = cardNumberWithSpaces
    
    if let targetPosition = textField.position(from: textField.beginningOfDocument, offset: targetCursorPosition) {
        textField.selectedTextRange = textField.textRange(from: targetPosition, to: targetPosition)
    }
}

func removeNonDigits(string: String, andPreserveCursorPosition cursorPosition: inout Int) -> String {
    var digitsOnlyString = ""
    let originalCursorPosition = cursorPosition
    
    for i in Swift.stride(from: 0, to: string.count, by: 1) {
        let characterToAdd = string[string.index(string.startIndex, offsetBy: i)]
        if characterToAdd >= "0" && characterToAdd <= "9" {
            digitsOnlyString.append(characterToAdd)
        }
        else if i < originalCursorPosition {
            cursorPosition -= 1
        }
    }
    
    return digitsOnlyString
}

func insertSpacesEveryFourDigitsIntoString(string: String, andPreserveCursorPosition cursorPosition: inout Int) -> String {
    var stringWithAddedSpaces = ""
    let cursorPositionInSpacelessString = cursorPosition
    
    for i in Swift.stride(from: 0, to: string.count, by: 1) {
        if i > 0 && (i % 4) == 0 {
            stringWithAddedSpaces.append(contentsOf: " ")
            if i < cursorPositionInSpacelessString {
                cursorPosition += 1
            }
        }
        let characterToAdd = string[string.index(string.startIndex, offsetBy: i)]
        stringWithAddedSpaces.append(characterToAdd)
    }
    
    return stringWithAddedSpaces
}

Answer 9

Swift 2中另一个接受的答案版本......

确保在委托实例中包含以下内容:

private var previousTextFieldContent: String?
private var previousSelection: UITextRange?

并确保您的文本字段调用reformatAsCardNumber:

textField.addTarget(self, action: #selector(reformatAsCardNumber(_:)), forControlEvents: .EditingChanged)

您的文本字段委托将需要这样做:

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    previousTextFieldContent = textField.text;
    previousSelection = textField.selectedTextRange;
    return true
}

最后包括以下方法:

func reformatAsCardNumber(textField: UITextField) {
    var targetCursorPosition = 0
    if let startPosition = textField.selectedTextRange?.start {
        targetCursorPosition = textField.offsetFromPosition(textField.beginningOfDocument, toPosition: startPosition)
    }

    var cardNumberWithoutSpaces = ""
    if let text = textField.text {
        cardNumberWithoutSpaces = self.removeNonDigits(text, andPreserveCursorPosition: &targetCursorPosition)
    }

    if cardNumberWithoutSpaces.characters.count > 19 {
        textField.text = previousTextFieldContent
        textField.selectedTextRange = previousSelection
        return
    }

    let cardNumberWithSpaces = self.insertSpacesEveryFourDigitsIntoString(cardNumberWithoutSpaces, andPreserveCursorPosition: &targetCursorPosition)
    textField.text = cardNumberWithSpaces

    if let targetPosition = textField.positionFromPosition(textField.beginningOfDocument, offset: targetCursorPosition) {
        textField.selectedTextRange = textField.textRangeFromPosition(targetPosition, toPosition: targetPosition)
    }
}

func removeNonDigits(string: String, inout andPreserveCursorPosition cursorPosition: Int) -> String {
    var digitsOnlyString = ""
    let originalCursorPosition = cursorPosition

    for i in 0.stride(to: string.characters.count, by: 1) {
        let characterToAdd = string[string.startIndex.advancedBy(i)]
        if characterToAdd >= "0" && characterToAdd <= "9" {
            digitsOnlyString.append(characterToAdd)
        }
        else if i < originalCursorPosition {
            cursorPosition -= 1
        }
    }

    return digitsOnlyString
}

func insertSpacesEveryFourDigitsIntoString(string: String, inout andPreserveCursorPosition cursorPosition: Int) -> String {
    var stringWithAddedSpaces = ""
    let cursorPositionInSpacelessString = cursorPosition

    for i in 0.stride(to: string.characters.count, by: 1) {
        if i > 0 && (i % 4) == 0 {
            stringWithAddedSpaces.appendContentsOf(" ")
            if i < cursorPositionInSpacelessString {
                cursorPosition += 1
            }
        }
        let characterToAdd = string[string.startIndex.advancedBy(i)]
        stringWithAddedSpaces.append(characterToAdd)
    }

    return stringWithAddedSpaces
}

Answer 10

所以我想用更少的代码来做到这一点，所以我在这里使用了代码，并重新调整了用途。屏幕上有两个字段，一个是数字，一个是到期日，所以我使它更具可重用性。

Swift 3替代答案

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    guard let currentText = (textField.text as NSString?)?.replacingCharacters(in: range, with: string) else { return true }

    if textField == cardNumberTextField {
        textField.text = currentText.grouping(every: 4, with: " ")
        return false
    }
    else { // Expiry Date Text Field
        textField.text = currentText.grouping(every: 2, with: "/")
        return false
    }
}

extension String {
    func grouping(every groupSize: String.IndexDistance, with separator: Character) -> String {
       let cleanedUpCopy = replacingOccurrences(of: String(separator), with: "")
       return String(cleanedUpCopy.characters.enumerated().map() {
            $0.offset % groupSize == 0 ? [separator, $0.element] : [$0.element]
       }.joined().dropFirst())
    }
}