/** 完成后执行的block */
@property (copy, nonatomic) void(^completionBlock)(NSInteger);
/** 是否可以点击 */
@property (assign, nonatomic) BOOL clickable;
/** 星星个数 */
@property (assign, nonatomic) NSInteger numberOfStars;
/** 星星边长 */
@property (assign, nonatomic) CGFloat lengthOfSide;
/** 评价值 */
@property (assign, nonatomic) NSInteger currentValue;
/** 星星间隔 */
@property (assign, nonatomic) CGFloat spacing;

- (void)setLengthOfSide:(CGFloat)lengthOfSide {

  // 超过控件高度
  if (lengthOfSide > self.frame.size.height) {
    lengthOfSide = self.frame.size.height;
  }

  // 超过控件宽度
  if (lengthOfSide > self.frame.size.width / _numberOfStars) {
    lengthOfSide = self.frame.size.width / _numberOfStars;
  }

  _lengthOfSide = lengthOfSide;
  _spacing = (self.frame.size.width - lengthOfSide * _numberOfStars) / _numberOfStars;

  [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect {

  UIImage *lightImage = [UIImage imageNamed:@"star_light"];
  UIImage *darkImage = [UIImage imageNamed:@"star_dark"];

  // 获取当前上下文
  CGContextRef context = UIGraphicsGetCurrentContext();

  for (int i = 0; i < self.numberOfStars; i ++) {
    // 根据 currentValue 选择是画亮的还是暗的星星
    UIImage *image = i >= self.currentValue ? darkImage : lightImage;
    CGRect imageRect = CGRectMake(self.spacing / 2 + (self.lengthOfSide + self.spacing) * i, (self.frame.size.height - self.lengthOfSide) / 2, self.lengthOfSide, self.lengthOfSide);

    CGContextSaveGState(context);

    // 坐标系Y轴是相反的，进行翻转
    CGContextScaleCTM(context, 1.0, - 1.0);
    CGContextTranslateCTM(context, 0, - rect.origin.y * 2 - rect.size.height);

    CGContextDrawImage(context, imageRect, image.CGImage);
    CGContextRestoreGState(context);
  }
}

#import "CYStarView.h"
// 初始化，传入必要参数
CYStarView *starView = [[CYStarView alloc] initWithFrame:frame numberOfStars:number lengthOfSide:length];
// 设置 clickable，评论界面设置为YES，展示界面设置为NO
self.starView.clickable = YES;
// 
// 设置 completionBlock
self.starView.completionBlock = ^(NSInteger currentValue) {
  // 点击后的操作放这里
};