Objective-C中的领域日期范围查询

Question

I'm working with Realm and I have an array sorted by dates for all the entries of a specific card. I need to create a NSPredicate (or some other way) that will give me all the dates for that card in order for a specific month. My trouble is some months have different amounts of days in them.

Here is what I have so far.

// Filter specific card, create date and string for x axis
NSString *filteredName = [NSString stringWithFormat:@"%@", self.cardType];
NSDate *dateElement = [[NSDate alloc]init];
NSString *datedString = [[NSString alloc]initWithFormat:@""];

//Formatting datedString
NSDateFormatter *df = [[NSDateFormatter alloc] init];
df.dateFormat = @"MM/dd/YYYY";

NSSortDescriptor *dateSort = [[NSSortDescriptor alloc]initWithKey:@"date" ascending:YES];
NSArray *sortedArray = @[dateSort];

//self.orderHistory is all of the cards from the Realm database filtered down to a specific type of card.
for (Order *uniqueOrder in [self.orderHistory objectsWhere:@"name = [c] %@", filteredName]) {
    // [self.uniqueCardArray addObject:uniqueOrder];
    dateElement = uniqueOrder.date;
    datedString = [df stringFromDate:dateElement];
    [self.uniqueDatesForCardArray addObject:datedString];

}
[self.uniqueCardArray sortUsingDescriptor:sortedArray];

Code above gives me all the dates for a specific card I need the dates for a given month so I have tried this tacky solution but I would think there is something more elegant to say the least.

NSDate *todaysDate = [NSDate date];
NSTimeInterval secondsInMonth =- (60 * 60 * 24 * 365) / 12;
NSDate *dateOneMonthBack = [todaysDate dateByAddingTimeInterval:secondsInMonth];

NSPredicate *backDatesPred = [NSPredicate predicateWithFormat: @"date BETWEEN {%@, %@}", dateOneMonthBack, todaysDate];

Besides it being nasty code it will also take me back a month from the current date and not only back to the start of the month. Been looking at the Realm documentation, NSCalendar stuff, and NSPredicate guide and now my head is swimming trying to count for all the possible problems that can go wrong with this. Any advice or code snippets would be a great help.

Answer 1

I'm not sure whether I understand your question correctly, the following code is what you want?

To determine the date of the previous month, add NSDateComponet that has minus month to the date.

Realm supports BETWEEN query. So you can just query by two days.

NSDate *todaysDate = [NSDate date];

NSDateComponents *comps = [NSDateComponents new];
comps.month = -1;

NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *dateOneMonthBack = [calendar dateByAddingComponents:comps toDate:todaysDate options:kNilOptions];

RLMResults *filteredHistory = [self.orderHistory objectsWhere:@"name = [c] %@", filteredName];
RLMResults *rangedHistory = [filteredHistory objectsWhere:@"date BETWEEN {%@, %@}", dateOneMonthBack, todaysDate];