Calculating the age of a person using two NSDates

Question

My class representing a person has a method to calculate that person's age:

@interface Student : NSObject

@property (strong) NSDate *dob;

// This method will work out the person's age in calendar years
- (NSDateComponents*)ageCalculation:(NSDate*)dob;

Here is the class implementation file

@implementation Student

- (NSDateComponents*)ageCalculation:(NSDate*)dob {
    NSDate *now = [NSDate date];
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSCalendarUnit units = NSYearCalendarUnit | NSMonthCalendarUnit;
    NSDateComponents *components = [calendar components:units 
                                               fromDate:dob 
                                                 toDate:now   
                                                options:0];
    return components;
}

@end

I'm not sure that I'm doing this right, though:

Student *student1 = [[Student alloc] init];
[student1 setDob:aDateOfBirth];
NSDateComponents *ageComponents = [student1 ageCalculation:aDateOfBirth];

What should I do with the result of this method? How can I make ageCalculation: use the date I already set?

Answer 1

There are a couple of things that can be noted. First of all, the code for computing the age is fine, except that I don't understand why you return NSDateComponents instead of just the age in years.

Here's how I would do it

- (NSInteger)age {
    NSDate *today = [NSDate date];
    NSDateComponents *ageComponents = [[NSCalendar currentCalendar]
                                       components:NSYearCalendarUnit
                                       fromDate:self.dob
                                       toDate:today
                                       options:0];
    return ageComponents.year;
}

You are interested only in the year component, so return it instead of NSDateComponents. Using self.dob instead of an argument gets the date you set earlier.

Answer 2

Just created a simple method that returns the age in years as a string.

-(NSString *) getAge:(NSDate *)dateOfBirth {

    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierIndian];
    NSDateComponents *components = [calendar components:NSYearCalendarUnit
                                               fromDate:dateOfBirth
                                                 toDate:[NSDate date]
                                                options:0];

    return [NSString stringWithFormat:@"%li",components.year];
    }

NOTE

1. This uses Indian Calendar - change it if u wish.
2. To call NSString *yearsOldinString = [self getAge:dateOfBirth];, where dateOfBirth represents person's date of birth in NSDate format.