ios - 比较uipickerdate和当前日期

Question

这是我为两个日期选择器提供的代码，需要使用if条件或开关将它们与当前日期进行比较。

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
dateFormatter.timeZone=[NSTimeZone defaultTimeZone];
dateFormatter.timeStyle=NSDateFormatterShortStyle;
dateFormatter.dateStyle=NSDateFormatterShortStyle;
NSString *dateTimeString=[dateFormatter stringFromDate:startTime.date];
NSLog(@"Start time is %@",dateTimeString);


NSDateFormatter *dateFormatter2 = [[NSDateFormatter alloc]init];
dateFormatter2.timeZone=[NSTimeZone defaultTimeZone];
dateFormatter2.timeStyle=NSDateFormatterShortStyle;
dateFormatter2.dateStyle=NSDateFormatterShortStyle;
NSString *dateTimeString2=[dateFormatter2 stringFromDate:endTime.date];
NSLog(@"End time is %@",dateTimeString2);

我的.h 中的

@property (weak, nonatomic) IBOutlet UIDatePicker *startTime;
@property (weak, nonatomic) IBOutlet UIDatePicker *endTime;

我怎么做？因为我只需要时间，我是否需要将它们存储到NSDate或NSTime？

另外， objective-c 是否存在If范围？

谢谢，

Answer 1

只需添加:

if ([[NSDate date] isEqualToDate:startTime.date]) {
NSLog(@"currentDate is equal to startTime"); 
}

if ([[NSDate date] isEqualToDate:endTime.date]) {
NSLog(@"currentDate is equal to endTime"); 
}

如果要计算两个日期之间的间隔，请使用此方法

- (NSTimeInterval)timeIntervalSinceDate:(NSDate *)anotherDate


if([startTime.date timeIntervalSinceDate:[NSDate date]] > 0)
{
  //start time greater than today
}

else if([startTime.date timeIntervalSinceDate:[NSDate date]] < 0)
{
    //start time less than today
}

else
{
   //both dates are equal
}

为了知道应用程序何时进入后台使用通知，请在您的viewDidLoad中添加此语句

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationEnteredBackground) name:UIApplicationDidEnterBackgroundNotification object:nil];

添加功能以在通知发布时满足通知

-(void)applicationEnteredBackground
{
   //do all the above steps here when you want.
}

并在该类的dealloc函数中删除观察者以进行通知

-(void)dealloc
{
  [[NSNotificationCenter defaultCenter] removeObserver:self];
}