NSDateFormatter用來設置NSDate的格式

-(NSString *)description

{

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

    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"]; //用來設置NSDate的輸出格式

    NSString *setTime=[formatter stringFromDate:self.time];

    NSString *setTime=[formatter stringFromDate:[NSDate date]];//用來說本地時間轉換成字符串的形式輸出

    return [NSString stringWithFormat:@"\ntitle:%@\ntime:%@\ncontents:%@\n",self.title,setTime,self.contents];

}