CODEWITHSUNDEEP
iosobjective-cnsdate
crzyonez777
crzyonez777

Reputation: 1807

Having trouble with initWithTimeInterval

I'm new to ios programming.

I'm trying to get the date of death by the code below. But, I get the unexpected result.

In the example code below, someone's birthdate is 1899-12-31 and this person's death age is 80.

So, I'm expecting this person's deathdate is 1979-12-31. But, the result I get is 1843-11-05 08:31:44 +0000.

Could anyone please tell me what's wrong with this code?

Thanks!!

NSInteger year = [_selectedDeathAge intValue];
NSLog(@"%d", year); //80

NSLog(@"%@", _selectedBirthDate);//(NSDate)1899-12-31 15:00:00 +0000 

NSDate *deathDate = [_selectedBirthDate initWithTimeInterval:year * 365 * 24 * 60 * 60 sinceDate:_selectedBirthDate];

NSLog(@"%@", deathDate);//(NSDate)1843-11-05 08:31:44 +0000

Upvotes: 1

Views: 465

Answers (3)

Jacob Relkin
Jacob Relkin

Reputation: 163268

Don't use NSDate to do relative date computations. Use NSCalendar and NSDateComponents:

NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *yearsComponents = [[NSDateComponents alloc] init];
yearsComponents.year = [_selectedDeathAge intValue];
NSDate *deathDate = [cal dateByAddingComponents:yearsComponents toDate:_selectedBirthDate];

Upvotes: 2

rmaddy
rmaddy

Reputation: 318854

You should not be calling the initWithTimeInterval:sinceDate: method on another instance.

You should be doing this instead:

NSDate *deathDate = [_selectedBirthDate dateByAddingTimeInterval:year * 365 * 24 * 60 * 60];

Or you can do it this way:

NSDate *deathDate = [[NSDate alloc] initWithWithTimeInterval:year * 365 * 24 * 60 * 60 sinceDate:_selectedBirthDate];

But in the end, you should use the solution from "Jacob Relkin". It's the better solution for this type of calculation.

Upvotes: 2

borrrden
borrrden

Reputation: 33421

NSDate *deathDate = [_selectedBirthDate initWithTimeInterval:year * 365 * 24 * 60 * 60 sinceDate:_selectedBirthDate];

This line is wrong, and you should expect strange results. You are calling init on an already initialized function. You need to create it via [[NSDate alloc] initWithTimeInterval:sinceDate:] and furthermore, you should not hardcode the time interval like that. Look up NSDateComponents.

Upvotes: 1

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