_testView = [[NNValidationView alloc] initWithFrame:CGRectMake((self.view.frame.size.width - 100) / 2, 200, 100, 40) andCharCount:4 andLineCount:4];
  [self.view addSubview:_testView];

 __weak typeof(self) weakSelf = self;
  /// 返回验证码数字
  _testView.changeValidationCodeBlock = ^(void){
    NSLog(@"验证码被点击了：%@", weakSelf.testView.charString);
  };

#pragma mark - 绘制界面
- (void)drawRect:(CGRect)rect {
  [super drawRect:rect];
  self.backgroundColor = NNRandomColor;
  CGFloat rectWidth = rect.size.width;
  CGFloat rectHeight = rect.size.height;
  CGFloat pointX, pointY;
  
  NSString *text = [NSString stringWithFormat:@"%@",self.charString];
  NSInteger charWidth = rectWidth / text.length - 15;
  NSInteger charHeight = rectHeight - 25;
  
  // 依次绘制文字
  for (NSInteger i = 0; i < text.length; i++) {
    // 文字X坐标
    pointX = arc4random() % charWidth + rectWidth / text.length * i;
    // 文字Y坐标
    pointY = arc4random() % charHeight;
    unichar charC = [text characterAtIndex:i];
    NSString *textC = [NSString stringWithFormat:@"%C", charC];

    [textC drawAtPoint:CGPointMake(pointX, pointY) withAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:arc4random() % 10 + 15]}];
  }
  
  // 获取上下文
  CGContextRef context = UIGraphicsGetCurrentContext();
  // 设置线宽
  CGContextSetLineWidth(context, 1.0);
  
  // 依次绘制直线
  for(NSInteger i = 0; i < self.lineCount; i++) {
    // 设置线的颜色
    CGContextSetStrokeColorWithColor(context, NNRandomColor.CGColor);
    // 设置线的起点
    pointX = arc4random() % (NSInteger)rectWidth;
    pointY = arc4random() % (NSInteger)rectHeight;
    CGContextMoveToPoint(context, pointX, pointY);
    // 设置线的终点
    pointX = arc4random() % (NSInteger)rectWidth;
    pointY = arc4random() % (NSInteger)rectHeight;
    CGContextAddLineToPoint(context, pointX, pointY);
    // 绘画路径
    CGContextStrokePath(context);
  }
}