IOS15实现经典登录页面，手机号带格式化功能

核心源码

#import "LJPhoneTextField.h"

// 设置RGB颜色
#define RGB(r,g,b) [UIColor colorWithRed:(r)/255.0f green:(g)/255.0f blue:(b)/255.0f alpha:1]

@implementation LJPhoneTextField

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.leftViewMode = UITextFieldViewModeAlways;
        self.clearButtonMode = UITextFieldViewModeWhileEditing;
        self.backgroundColor = [UIColor whiteColor];
        self.textColor = RGB(51,51,51);
          [self addTarget:self action:@selector(reformatAsPhoneNumber:) forControlEvents:UIControlEventEditingChanged];
    }
    return self;
}
- (instancetype)initWithCoder:(NSCoder *)coder
{
    self = [super initWithCoder:coder];
    if (self) {
        [self addTarget:self action:@selector(reformatAsPhoneNumber:) forControlEvents:UIControlEventEditingChanged];
    }
    return self;
}
-(void)reformatAsPhoneNumber:(UITextField *)textField {
    /**
     *  判断正确的光标位置
     */
    NSUInteger targetCursorPostion = [textField offsetFromPosition:textField.beginningOfDocument toPosition:textField.selectedTextRange.start];
    NSString *phoneNumberWithoutSpaces = [self removeNonDigits:textField.text andPreserveCursorPosition:&targetCursorPostion];
    
    if([phoneNumberWithoutSpaces length]>11) {
        /**
         *  避免超过11位的输入
         */
        [textField setText:_previousTextFieldContent];
        textField.selectedTextRange = _previousSelection;
        return;
    }
    
    NSString *phoneNumberWithSpaces = [self insertSpacesEveryFourDigitsIntoString:phoneNumberWithoutSpaces andPreserveCursorPosition:&targetCursorPostion];
    
    textField.text = phoneNumberWithSpaces;
    UITextPosition *targetPostion = [textField positionFromPosition:textField.beginningOfDocument offset:targetCursorPostion];
    [textField setSelectedTextRange:[textField textRangeFromPosition:targetPostion toPosition:targetPostion]];
    
}
/**
 *  除去非数字字符，确定光标正确位置
 *
 *  @param string         当前的string
 *  @param cursorPosition 光标位置
 *
 *  @return 处理过后的string
 */
- (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;
}

/**
 *  将空格插入我们现在的string 中，并确定我们光标的正确位置，防止在空格中
 *
 *  @param string         当前的string
 *  @param cursorPosition 光标位置
 *
 *  @return 处理后有空格的string
 */
- (NSString *)insertSpacesEveryFourDigitsIntoString:(NSString *)string andPreserveCursorPosition:(NSUInteger *)cursorPosition{
    NSMutableString *stringWithAddedSpaces = [NSMutableString new];
    NSUInteger cursorPositionInSpacelessString = *cursorPosition;
    
    for (NSUInteger i=0; i<string.length; i++) {
        if(i>0)
        {
            if(i==3 || i==7) {
                [stringWithAddedSpaces appendString:@" "];
                
                if(i<cursorPositionInSpacelessString) {
                    (*cursorPosition)++;
                }
            }
        }
        
        unichar characterToAdd = [string characterAtIndex:i];
        NSString *stringToAdd = [NSString stringWithCharacters:&characterToAdd length:1];
        [stringWithAddedSpaces appendString:stringToAdd];
    }
    return stringWithAddedSpaces;
}

#pragma mark - UITextFieldDelegate
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    _previousSelection = textField.selectedTextRange;
    _previousTextFieldContent = textField.text;
        if(range.location==0) {
            if(string.integerValue >1)
            {
                return NO;
            }
        }
    
    return YES;
}

@end