iOS中类似微信红点显示功能

#import <UIKit/UIKit.h>@interface UIView (CHRRedDot)@property (readonly, nonatomic) CALayer * chr_redDotLayer;/** 红点圆心的位置，与各个边之间的距离。如果距离<=0，则忽略距离 */@property (nonatomic, assign) UIEdgeInsets chr_redDotEdgeInsets;/** 红点的半径，默认为4 */@property (nonatomic, assign) CGFloat chr_redDotRadius;/** 红点的颜色，默认为0xFF5A5A */@property (nonatomic, strong) UIColor * chr_redDotColor;/** 红点是否显示 */@property (nonatomic, assign) BOOL chr_redDotShow;@end#pragma mark - method- (void)chr_updateRedDot {  CALayer *redDot = self.chr_redDotLayer;  if (self.chr_redDotShow) {    if (redDot == nil) {      redDot = [CALayer layer];      self.chr_redDotLayer = redDot;      [self.layer addSublayer:redDot];    }    redDot.backgroundColor = self.chr_redDotColor.CGColor;    [self chr_layoutRedDot];  } else {    [redDot removeFromSuperlayer];    self.chr_redDotLayer = nil;  }}- (void)chr_layoutRedDot {  CALayer *redDot = self.chr_redDotLayer;  if (redDot == nil) return;  CGFloat radius = self.chr_redDotRadius;  redDot.cornerRadius = radius;  UIEdgeInsets edgeInsets = self.chr_redDotEdgeInsets;  CGFloat originX = edgeInsets.right <= 0 ? edgeInsets.left - radius : self.bounds.size.width - edgeInsets.right + radius;  CGFloat originY = edgeInsets.bottom <= 0 ? edgeInsets.top - radius : self.bounds.size.height - edgeInsets.bottom + radius;  CGFloat length = radius * 2;  redDot.frame = CGRectMake(originX, originY, length, length);}