NSDate, comparing two dates [duplicate]

问题

This question already has an answer here:

How to compare two dates in Objective-C 14 answers

Ok, I have been working on this for a couple of days now and am stuck. What I am trying to do is compare the current time with a predetermined time. What I want to happen is, Everyday at certain times I want certain code to fire, but not before the time of day that I specify.

so, basically if the "current time" is the same or equal to "predetermined time" then fire this code. Or fire this line of code.

Sounds simple, but I am having trouble grabbing comparing the two times.

I have formatted a string to a date like so

     NSString* dateString = @"11:05 PM";
        NSDateFormatter* firstDateFormatter = [[[NSDateFormatter alloc] init] autorelease];
        [firstDateFormatter setDateFormat:@"h:mm a"];
        [firstDateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
        NSDate* date = [firstDateFormatter dateFromString:dateString];
        NSLog(@"date %@",date);

then i grab the current time like so

   NSDate *currentTime = [NSDate dateWithTimeIntervalSinceNow:[[NSTimeZone localTimeZone]     secondsFromGMT]];
NSDateComponents* comps = [[NSCalendar currentCalendar] 
                           components: NSHourCalendarUnit |NSMinuteCalendarUnit 
                                |NSSecondCalendarUnit fromDate:currentTime];
 [[NSCalendar currentCalendar] dateFromComponents:comps];

SO how do I compare these two times? I have tried everything I can think of, please help.

回答1:

Can you try below lines of code?

switch ([dateOne compare:dateTwo]){
     case NSOrderedAscending:
          NSLog(@"NSOrderedAscending");
    break;
    case NSOrderedSame:
          NSLog(@"NSOrderedSame");
    break;
    case NSOrderedDescending:
         NSLog(@"NSOrderedDescending");
    break;
}

But in your case I think you need to keep both dates in same format ..or some thing like this

 NSDateComponents *components = [[NSCalendar currentCalendar] components:NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit fromDate:[NSDate date]];
    [components setHour:23];//change your time to 24hrs formate 
    [components setMinute:05];
    [components setSecond:00];


    NSDate *dateOne = [[NSCalendar currentCalendar] dateFromComponents:components];

    components = [[NSCalendar currentCalendar] components:NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit fromDate:[NSDate date]];

     NSDate *dateTwo = [[NSCalendar currentCalendar] dateFromComponents:components];

and do comparison between dateOne and dateTwo.

回答2:

Try this condition:

if ([date compare:currentTime]==NSOrderedSame) {

         //do want you want
}

回答3:

Assuming your issue is actually comparing the two NSDate objects, try checking out the question linked below; it has some good pointers;

How to compare two dates in Objective-C

来源：https://stackoverflow.com/questions/9781467/nsdate-comparing-two-dates

标签

iphone

ios

sdk

nsdate