在输入银行卡号的时候, 一般都要求输入4位自动空格. 最近项目里,有个输入的, 输入时候,把光标移到TextField中间. 输入数字, 会错乱, 从网上找了人家封装好的.改了改, 若复制中文, 则粘贴不上.
封装的类名叫 BankCardTextField

直接粘贴代码吧
BankCardTextField.h

//
//  BankCardTextField.h
//  TextFieldDmo
//
//  Created by  on 2019/5/23.
//  Copyright © 2019 . All rights reserved.
//

#import <UIKit/UIKit.h>


NS_ASSUME_NONNULL_BEGIN


@interface BankCardTextField : UITextField
/**
 *  默认为4，即4个数一组 用空格分隔
 */
@property (assign, nonatomic) NSInteger groupSize;

/**
 *  分隔符 默认为空格
 */
@property (copy, nonatomic) NSString *separator;

@end

@interface UITextField (WYRange)

- (NSRange)selectedRange;

- (void)setSelectedRange:(NSRange)range;

- (void)bankNoshouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;
@end
NS_ASSUME_NONNULL_END

bankCardTextField.m

//
//  BankCardTextField.m
//  TextFieldDmo
//
//  Created by on 2019/5/23.
//  Copyright © 2019 . All rights reserved.
//

#import "BankCardTextField.h"

@implementation BankCardTextField

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (!self) {
        return nil;
    }
    _groupSize = 4;
    _separator = @" ";
    return self;
}
- (NSRange)selectedRange {
    UITextPosition *beginning = self.beginningOfDocument;
    UITextRange *selectedRange = self.selectedTextRange;
    UITextPosition *selectionStart = selectedRange.start;
    UITextPosition *selectionEnd = selectedRange.end;
    const NSInteger location = [self offsetFromPosition:beginning toPosition:selectionStart];
    const NSInteger length = [self offsetFromPosition:selectionStart toPosition:selectionEnd];
    return NSMakeRange(location, length);
}
- (void)setSelectedRange:(NSRange)range {
    UITextPosition *beginning = self.beginningOfDocument;
    UITextPosition *startPosition = [self positionFromPosition:beginning offset:range.location];
    UITextPosition *endPosition = [self positionFromPosition:beginning offset:range.location + range.length];
    UITextRange *selectionRange = [self textRangeFromPosition:startPosition toPosition:endPosition];
    [self setSelectedTextRange:selectionRange];
}

- (void)bankNoshouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSInteger groupSize = self.groupSize;
    NSString *text = self.text;
    NSString *beingString = [self.text stringByReplacingCharactersInRange:range withString:string];
    NSString *cardNo = [self removingSapceString:beingString];
    //校验卡号只能是数字，且不能超过20位
    if ( (string.length != 0 && ![self isValidNumbers:cardNo]) || cardNo.length > 20) {
        return;
    }
    //获取【光标右侧的数字个数】
    NSInteger rightNumberCount = [self removingSapceString:[text substringFromIndex:self.selectedRange.location + self.selectedRange.length]].length;
    //输入长度大于4 需要对数字进行分组，每4个一组，用空格隔开
    if (beingString.length > groupSize) {
        self.text = [self groupedString:beingString];
    } else {
        self.text = beingString;
    }
    text = self.text;
    /**
     * 计算光标位置(相对末尾)
     * 光标右侧空格数 = 所有的空格数 - 光标左侧的空格数
     * 光标位置 = 【光标右侧的数字个数】+ 光标右侧空格数
     */
    NSInteger rightOffset = [self rightOffsetWithCardNoLength:cardNo.length rightNumberCount:rightNumberCount];
    NSRange currentSelectedRange = NSMakeRange(text.length - rightOffset, 0);
    
    //如果光标左侧是一个空格，则光标回退一格
    if (currentSelectedRange.location > 0 && [[text substringWithRange:NSMakeRange(currentSelectedRange.location - 1, 1)] isEqualToString:self.separator]) {
        currentSelectedRange.location -= 1;
    }
    [self setSelectedRange:currentSelectedRange];
}

#pragma mark - Helper
/**
 *  计算光标相对末尾的位置偏移
 *
 *  @param length           卡号的长度(不包括空格)
 *  @param rightNumberCount 光标右侧的数字个数
 *
 *  @return 光标相对末尾的位置偏移
 */
- (NSInteger)rightOffsetWithCardNoLength:(NSInteger)length rightNumberCount:(NSInteger)rightNumberCount {
    NSInteger totalGroupCount = [self groupCountWithLength:length];
    NSInteger leftGroupCount = [self groupCountWithLength:length - rightNumberCount];
    NSInteger totalWhiteSpace = totalGroupCount -1 > 0? totalGroupCount - 1 : 0;
    NSInteger leftWhiteSpace = leftGroupCount -1 > 0? leftGroupCount - 1 : 0;
    return rightNumberCount + (totalWhiteSpace - leftWhiteSpace);
}

/**
 *  校验给定字符串是否是纯数字
 *
 *  @param numberStr 字符串
 *
 *  @return 字符串是否是纯数字
 */
- (BOOL)isValidNumbers:(NSString *)numberStr {
    NSString* numberRegex = @"^[0-9]+$";
    NSPredicate *numberPre = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",numberRegex];
    return [numberPre evaluateWithObject:numberStr];
}

/**
 *  去除字符串中包含的空格
 *
 *  @param str 字符串
 *
 *  @return 去除空格后的字符串
 */
- (NSString *)removingSapceString:(NSString *)str {
    return [str stringByReplacingOccurrencesOfString:self.separator withString:@"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, str.length)];
}

/**
 *  根据长度计算分组的个数
 *
 *  @param length 长度
 *
 *  @return 分组的个数
 */
- (NSInteger)groupCountWithLength:(NSInteger)length {
    return (NSInteger)ceilf((CGFloat)length /self.groupSize);
}

/**
 *  给定字符串根据指定的个数进行分组，每一组用空格分隔
 *
 *  @param string 字符串
 *
 *  @return 分组后的字符串
 */
- (NSString *)groupedString:(NSString *)string {
    NSString *str = [self removingSapceString:string];
    NSInteger groupCount = [self groupCountWithLength:str.length];
    NSInteger groupSize = self.groupSize;
    NSMutableArray *components = [[NSMutableArray alloc] init];
    for (NSInteger i = 0; i < groupCount; i++) {
        if (i*groupSize + groupSize > str.length) {
            [components addObject:[str substringFromIndex:i*groupSize]];
        } else {
            [components addObject:[str substringWithRange:NSMakeRange(i*groupSize, groupSize)]];
        }
    }
    NSString *groupedString = [components componentsJoinedByString:self.separator];
    return groupedString;
}

@end

@implementation BankCardTextField (WYRange)

- (NSRange)selectedRange {
    UITextPosition *beginning = self.beginningOfDocument;
    UITextRange *selectedRange = self.selectedTextRange;
    UITextPosition *selectionStart = selectedRange.start;
    UITextPosition *selectionEnd = selectedRange.end;
    const NSInteger location = [self offsetFromPosition:beginning toPosition:selectionStart];
    const NSInteger length = [self offsetFromPosition:selectionStart toPosition:selectionEnd];
    return NSMakeRange(location, length);
}

- (void)setSelectedRange:(NSRange)range {
    UITextPosition *beginning = self.beginningOfDocument;
    UITextPosition *startPosition = [self positionFromPosition:beginning offset:range.location];
    UITextPosition *endPosition = [self positionFromPosition:beginning offset:range.location + range.length];
    UITextRange *selectionRange = [self textRangeFromPosition:startPosition toPosition:endPosition];
    [self setSelectedTextRange:selectionRange];
}

@end

用法:

#import "ViewController.h"
#import "BankCardTextField.h"
@interface ViewController ()<UITextFieldDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    BankCardTextField *cardTF = [[BankCardTextField alloc] initWithFrame:CGRectMake(100, 200, 180, 50)];
    cardTF.placeholder = @"请输入银行卡号";
    cardTF.textColor = [UIColor blackColor];
    cardTF.borderStyle = UITextBorderStyleLine;
    cardTF.delegate = self;
    [self.view addSubview:cardTF];
}
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    [textField bankNoshouldChangeCharactersInRange:range replacementString:string];
    return NO;
}

@end