监听UITextfield值变化

_phoneNumTextfield.delegate = self;
        //textField变化时事件
        [_phoneNumTextfield addTarget:self action:@selector(textFieldEditingChanged:) forControlEvents:UIControlEventEditingChanged];

定义成员变量

    NSString *previousTextFieldContent;
    UITextRange *previousSelection;

代理方法

- (void)textFieldEditingChanged:(UITextField *)textField {
    //限制手机账号长度13位（有两个空格）
    if (textField.text.length > 13) {
        textField.text = [textField.text substringToIndex:13];
    }
    
    NSUInteger targetCursorPosition = [textField offsetFromPosition:textField.beginningOfDocument toPosition:textField.selectedTextRange.start];
    
    NSString *currentStr = [textField.text stringByReplacingOccurrencesOfString:@" " withString:@""];
    NSString *preStr = [previousTextFieldContent stringByReplacingOccurrencesOfString:@" " withString:@""];
    
    //正在执行删除操作时为0，否则为1
    char editFlag = 0;
    if (currentStr.length <= preStr.length) {
        editFlag = 0;
    } editFlag = 1;
    
    
    NSMutableString *tempStr = [NSMutableString new];
    
    int spaceCount = 0;
    if (currentStr.length < 3 && currentStr.length > -1) {
        spaceCount = 0;
    }else if (currentStr.length < 7 && currentStr.length > 2) {
        spaceCount = 1;
    }else if (currentStr.length < 12 && currentStr.length > 6) {
        spaceCount = 2;
    }
    
    for (int i = 0; i < spaceCount; i++) {
        if (i == 0) {
            [tempStr appendFormat:@"%@%@", [currentStr substringWithRange:NSMakeRange(0, 3)], @" "];
        }else if (i == 1) {
            [tempStr appendFormat:@"%@%@", [currentStr substringWithRange:NSMakeRange(3, 4)], @" "];
        }else if (i == 2) {
            [tempStr appendFormat:@"%@%@", [currentStr substringWithRange:NSMakeRange(7, 4)], @" "];
        }
    }
    
    if (currentStr.length == 11) {
        [tempStr appendFormat:@"%@%@", [currentStr substringWithRange:NSMakeRange(7, 4)], @" "];
    }
    if (currentStr.length < 4) {
        [tempStr appendString:[currentStr substringWithRange:NSMakeRange(currentStr.length - currentStr.length % 3, currentStr.length % 3)]];
    }else if(currentStr.length > 3 && currentStr.length <12) {
        NSString *str = [currentStr substringFromIndex:3];
        [tempStr appendString:[str substringWithRange:NSMakeRange(str.length - str.length % 4, str.length % 4)]];
        if (currentStr.length == 11) {
            [tempStr deleteCharactersInRange:NSMakeRange(13, 1)];
        }
    }
    textField.text = tempStr;
    // 当前光标的偏移位置
    NSUInteger curTargetCursorPosition = targetCursorPosition;
    
    if (editFlag == 0) {
        //删除
        if (targetCursorPosition == 9 || targetCursorPosition == 4) {
            curTargetCursorPosition = targetCursorPosition - 1;
        }
    }else {
        //添加
        if (currentStr.length == 8 || currentStr.length == 4) {
            curTargetCursorPosition = targetCursorPosition + 1;
        }
    }
    UITextPosition *targetPosition = [textField positionFromPosition:[textField beginningOfDocument] offset:curTargetCursorPosition];
    [textField setSelectedTextRange:[textField textRangeFromPosition:targetPosition toPosition :targetPosition]];
}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    previousTextFieldContent = textField.text;
    previousSelection = textField.selectedTextRange;
    return YES;
}

试试吧