使用NSPredicate过滤包含带有NSDate字段的对象的NSArray

Question

I have an array of objects, with each object containing a field called date. I want to create a subset of this array using NSPredicate where I pull only those objects that fall within a certain date range. Here's the code I am using:

predicate = [NSPredicate predicateWithFormat:@"(date >= %@) AND (date =< %@)", startDate, endDate];
_daysArray = [_cachedDaysArray filteredArrayUsingPredicate:predicate];

The problem I am having is when startDate and endDate are the same day, but different times. Here's the variables view in the XCode debugger

As you can see, I have an object in the array that has a date field equal to startDate , but you can also see that _daysArray contains no elements after the filter is executed.

This works fine when the dates are not the same day.

Any help would be greatly appreciated.

EDIT #1

Here's the po of the predicate variable as requested by commenter:

(lldb) po predicate
date >= CAST(406616400.676014, "NSDate") AND date <= CAST(406702799.677098, "NSDate")
(lldb)

EDIT #2

(lldb) po [[_cachedDaysArray firstObject] date]
2013-11-18 05:00:00 +0000
(lldb) 

EDIT #3

Martin R. got me on the right track with his comment on how startDate was being calculated. Now that I have changed that, it's working. I am using a method to calculate startDate . Previously, I was using NSUIntegerMax to indicate the components, now I am breaking them out specifically:

-(NSDate *)pastDate:(NSInteger)daysPast
{
    // Get the appropriate calendar
    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDateComponents *startComponents = [calendar components:(NSCalendarUnitMonth|NSCalendarUnitDay|NSCalendarUnitYear|NSCalendarUnitHour|NSCalendarUnitMinute|NSCalendarUnitSecond) fromDate:[NSDate date]];
    [startComponents setHour: 00];
    [startComponents setMinute: 00];
    [startComponents setSecond: 00];
    startComponents.day = startComponents.day - daysPast;

    return [calendar dateFromComponents:startComponents];
}

Answer 1

From the output of the predicate

date >= CAST(406616400.676014, "NSDate") AND date <= CAST(406702799.677098, "NSDate")

one can see that startDate is not exactly "2013-11-20 05:00:00 +0000" (UTC) or "2013-11-20 00:00:00" (EST) but 0.676014 seconds later . Therefore, if the date of the object in _cachedDaysArray falls exactly on midnight of 2013-11-20, it does not match the predicate.

It seems that the calculation of startDate and endDate does not exactly what you expect.

Answer 2

You should convert your dates to do not include time, before you pass it to your predicate. Try this:

-(NSDate*)dateNoTime:(NSDate*)myDate
{

NSDateComponents *comp = [[NSCalendar currentCalendar] components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate: myDate];
return [[NSCalendar currentCalendar] dateFromComponents:comp];

}

Answer 3

Try this:

predicate =[NSPredicate predicateWithBlock:^BOOL(TRDay *evaluatedObject, NSDictionary *bindings) {
    return evaluatedObject.date.timeIntervalSince1970 >= startDate.timeIntervalSince1970 && evaluatedObject.date.timeIntervalSince1970 <= endDate.timeIntervalSince1970;
}];

Answer 4

I tried something like that:

NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];

NSDateComponents *components3 = [[NSDateComponents alloc] init];
[components3 setYear:2013];
[components3 setMonth:11];
[components3 setDay:20];
NSDate *startDate = [gregorianCalendar dateFromComponents:components3];

[components3 setHour:23];
[components3 setMinute:59];
[components3 setSecond:59];

NSDate *endDate = [gregorianCalendar dateFromComponents:components3];
[gregorianCalendar release];

NSDictionary* dict = [NSDictionary dictionaryWithObjects:@[startDate] forKeys:@[@"date"]];
NSArray* mainArray = [NSArray arrayWithObjects:dict, nil];

NSPredicate* pred = [NSPredicate predicateWithFormat:@"(date >= %@) AND (date =< %@)", startDate, endDate];
NSArray* filteredArray = [mainArray filteredArrayUsingPredicate:pred];

And it works as expected. Basically it means you have error somewhere else.