CODEWITHSUNDEEP
iosnsdate
kas-kad
kas-kad

Reputation: 3764

NSDate comparison fails

Here is the code, that brought me some problems:

    NSDate * d1 = [NSDate dateWithTimeIntervalSinceReferenceDate:444555883.659000];
    NSTimeInterval since1970 = [d1 timeIntervalSince1970];
    NSDate * d2 = [NSDate dateWithTimeIntervalSince1970:since1970];

    NSLog(@"%@\n%@", d1, d2);
    NSLog(@"%d", [d1 compare: d2] == NSOrderedSame);

The problem I can't understand is that the test fails with following logs:

2015-02-02 07:44:43 +0000
2015-02-02 07:44:43 +0000

0 // test failed

What can be the reason of test fails?

Upvotes: 0

Views: 143

Answers (2)

Cihan Tek
Cihan Tek

Reputation: 5409

You're comparing double's, so you can't simply check for equality. The fact that both instances print out the same output doesn't mean anything because the precision of the default output format is 1 second.

Compare them by doing something like this:

if (fabs(t1 - t2) < delta)

where delta is very small amount such as 0.005

Or you can set the higher precision components of the date you don't need to 0 using NSDateComponents before comparing them

Upvotes: 0

Hot Licks
Hot Licks

Reputation: 47729

if (interval1 + delta > interval2 && interval1 - delta < interval2)

(You can do it directly with NSDates by adding/subtracting delta on the dates, but it's messier and I'm too lazy to write it out.)

Upvotes: 1

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