oc之获取系统当前时间的方法
NSDate *date = [NSDate date];//这个是NSDate类型的日期,所要获取的年月日都放在这里; NSCalendar *cal = [NSCalendar currentCalendar]; unsigned int unitFlags = NSCalendarUnitYear|NSCalendarUnitMonth| NSCalendarUnitDay;//这句是说你要获取日期的元素有哪些。获取年就要写NSYearCalendarUnit,获取小时就要写NSHourCalendarUnit,中间用|隔开;
NSDateComponents *d = [cal components:unitFlags fromDate:date];//把要从date中获取的unitFlags标示的日期元素存放在NSDateComponents类型的d里面; //然后就可以从d中获取具体的年月日了;
NSInteger year = [d year];
NSInteger month = [d month];
NSInteger day = [d day];
NSLog(@"%ld",year);
NSLog(@"%ld",month);
NSLog(@"%ld",day);