//date根据formatter转换成string+(NSString*)dateToString:(NSString *)formatter date:(NSDate *)date{    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];    [dateFormatter setDateFormat:formatter];    return[dateFormatter stringFromDate:date];}//string类型的时间戳转换成时间+(NSString*)dateStringToString:(NSString *)dateStr{    if ([dateStr isKindOfClass:[NSNull class]]) {        return nil;    } else {        NSInteger time = [dateStr intValue];        NSDate *date = [NSDate dateWithTimeIntervalSince1970:time];        NSString *timestr = [NSString stringWithFormat:@"%@",date];        NSRange rang;        rang.location = 0;O        rang.length = 10;        NSString *needtime = [timestr substringWithRange:rang];        return needtime;    }}//将日期从原格式转换成需要的格式+(NSString*)convertDateFormatter:(NSString*)sourceFormatter targetFormatter:(NSString*)targetFormatter dateString:(NSString*)dateString{    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];    [dateFormatter setDateFormat:sourceFormatter];    NSDate *date = [dateFormatter dateFromString:dateString];    [dateFormatter setDateFormat:targetFormatter];    return[dateFormatter stringFromDate:date];}//将日期字符串转换成date+(NSDate *)stringToDate:(NSString *)formatter dateString:(NSString *)dateString{    NSDateFormatter *dateFormatter= [[NSDateFormatter alloc] init];    [dateFormatter setDateFormat:formatter];    return [dateFormatter dateFromString:dateString];}