获取昨天的时间

+ (NSString *)yesterdayDate

{

   NSDate *yesterday = [NSDatedateWithTimeIntervalSinceNow:-(24*60*60)];

    NSDateFormatter *formatter = [[NSDateFormatter alloc]  init ];

    [formattersetDateFormat:@"yyyy-MM-dd"];

    

   NSString *yesterdayTime = [formatter stringFromDate:yesterday];

    

   return yesterdayTime;

}