loading upcoming events by comparing their dates with the calendar date - ios

Question

I have found the below code online for comparing two dates (the date of the calendar and some another date) what I would like help with is modifying this code so that it compares the calendar date with the date of an event where date here is key for each event within NSArray (json file) .. Also how I could use this later with NSPredicate so that I can load only the events with components (difference between two dates in days) at least more than 1 day since Im going to have UIButton called future events when the user click on it, all the future events should be loaded .. I would really appreciate any help and code examples since Im very new to objective C and Xcode. Thanks.
#implementation HomeViewController {
NSArray *_events;
}
- (BOOL)isSameDay:(NSDate*)date
{
NSCalendar* calendar = [NSCalendar currentCalendar];
NSDate *currDate = [NSDate date];
//date = [_events objectAtIndex:date];
unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents* comp1 = [calendar components:unitFlags fromDate:date];
NSDateComponents* comp2 = [calendar components:unitFlags fromDate:currDate];
NSDateComponents *components = [calendar components:unitFlags
fromDate:currDate
toDate:date
options:0];
NSLog(#"Days between dates: %#", components);
return [comp1 day] == [comp2 day] &&
[comp1 month] == [comp2 month] &&
[comp1 year] == [comp2 year];
}

Answer 1

To get the number of days remaining for a date from now, you can use the method below:
-(long)daysRemaining:(NSDate*) date
{
NSDate *now = [NSDate date];
NSTimeInterval dateDiff = [date timeIntervalSinceNow] - [now timeIntervalSinceNow];
CGFloat numberOfDaysRemaining = (dateDiff/(60*60*24));
return ceil(numberOfDaysRemaining);
}
So you can call to get the number of days remaining like this:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd"];
NSDate *dateToCompare = [dateFormatter dateFromString: #"2014-02-08"];
long numberDays = [self daysRemaining:dateToCompare];
For this case, the result is 2 days remaining. Note that a negative result indicates that was passed n days.
To filter the array (2 days remaining events) making a copy of it:
NSArray* dates = [[NSArray alloc] initWithObjects:
[dateFormatter dateFromString: #"2014-02-08"],
[dateFormatter dateFromString: #"2014-02-05"],
[dateFormatter dateFromString: #"2014-02-10"],
[dateFormatter dateFromString: #"2014-02-08"], nil];
NSArray *filteredArray = [dates filteredArrayUsingPredicate:
[NSPredicate predicateWithBlock:
^BOOL(id evaluatedObject, NSDictionary *bindings) {
long daysRemaining = [self daysRemaining:(NSDate*)evaluatedObject];
return daysRemaining == 2; // if someMethod returns YES, the object is kept
}
]];
To filter an NSMutableArray in place:
[mutableArray filterUsingPredicate:[NSPredicate predicateWithBlock:
^BOOL(id evaluatedObject, NSDictionary *bindings) {
long daysRemaining = [self daysRemaining:(NSDate*)evaluatedObject];
return daysRemaining == 2; // if someMethod returns YES, the object is kept
}
]];

Answer 2

[displayedEvents addObjectsFromArray:[_events filteredArrayUsingPredicate:
[NSPredicate predicateWithBlock:
^BOOL(Events * event, NSDictionary *bindings) {
[dateFormatter dateFromString: event.date];
long daysRemaining = [self daysRemaining: (NSDate*)event.date];
return daysRemaining > 1; // if someMethod returns YES, the object is kept
}
]]];