Check if an array of custom objects contains an object with a certain date

问题

I have an array of event objects. The object has several attributes. One of the attributes is an NSDate eve_date.

Now I want to check if that array of objects contains a certain NSDate d

I'm doing the following

if([[matches valueForKey:@"eve_date"] containsObject:d]){
        NSLog(@"contains object");
   }else{
    NSLog(@"does not contains object");
   }

But this is not working. Can anyone help me ?

Kind regards

EDIT

Okay let me be more clear. I'm making a calendar app. I fetched all the events inside the particular month. What I need to do now is to place a marker on my calendar on the correct date. Therefore I have this in a function.

NSLog(@"Delegate Range: %@ %@ %d",start,end,[start daysBetweenDate:end]);

    self.dataArray = [NSMutableArray array];
    self.dataDictionary = [NSMutableDictionary dictionary];

    NSDate *d = start;
    while(YES){
        for (Event *event in matches) {
            if([event.eve_date isEqualToDate:d]){
                //  (self.dataDictionary)[d] = save event title in here
                [self.dataArray addObject:@YES]; //place marker on date 'd'


            }else{
                [self.dataArray addObject:@NO]; // don't place marker
            }
        }


        NSDateComponents *info = [d dateComponentsWithTimeZone:calendar.timeZone];
        info.day++;
        d = [NSDate dateWithDateComponents:info];
        if([d compare:end]==NSOrderedDescending) break;
    }

But now I'm looping 31 times (amount of days off the month) through my array of events. (This is probably not the best practice solution ???)

I also think that the problem is that the time of the date is not the same. For example:

eve_date --> 2013-08-13 12:00
d --> 2013-08-13 15:00

So I probably should use an NSDateformatter to only get the date itself without the time ?

Am I correct ?

回答1:

I'm not very well versed with KVC, but if the solution doesn't need to use KVC, you can just iterate:

NSDate *dateToCompare = ...;
BOOL containsObject = NO;
for (MyEvent *e in matches)
{
    if ([e.eve_date isEqualToDate:dateToCompare]) 
    { 
        containsObject = YES;
        break;
    }
}

if (containsObject) NSLog(@"Contains Object");
else NSLog(@"Doesn't contain object");

I've had a play about with KVC and attempted a solution with that too. You were only missing valueForKeyPath instead of valueForKey

if ([[matches valueForKeyPath:@"eve_date"] containsObject:d])
{
    NSLog(@"Contains object");
}
else
{
    NSLog(@"Does not contain object");
}

回答2:

NSDate is an absolute point in time. To check if a date falls on a given day, you have to compare it with the "beginning of the day" and "beginning of the next day".

The following (pseudo-) code should demonstrate the idea:

NSDate *start, *end; // your given range

NSDate *currentDay = "beginning of" start;
// while currentDay < end:
while ([currentDay compare:end] == NSOrderedAscending) {
    NSDate *nextDay = currentDay "plus one day";
    for (Event *event in matches) {
        // if currentDay <= event.eve_date < nextDay:
        if ([event.eve_date compare:currentDay] != NSOrderedAscending
            && [event.eve_date compare:nextDay] == NSOrderedAscending) {
            // ...
        }
    }
    currentDay = nextDay;
}

The "beginning of a day" can be computed as follows:

NSCalendar *cal = [NSCalendar currentCalendar];
NSDate *aDate = ...;
NSDate *beginningOfDay;
[cal rangeOfUnit:NSDayCalendarUnit startDate:&beginningOfDay interval:NULL forDate:aDate];

来源：https://stackoverflow.com/questions/18332769/check-if-an-array-of-custom-objects-contains-an-object-with-a-certain-date

标签

iphone

ios

objective-c

nsdate

nsobject