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POObjective-C Fastest Way to find Closest NSDate in NSArray
 

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  1. POObjective-C Fastest Way to find Closest NSDate in NSArray
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    <p>I pass in an NSDate to the following function and want to find the NSDate in the array that is closest in time to the passed in value. </p> <p>Please note that I do not want to know if the array contains the exact date like this post: <a href="https://stackoverflow.com/questions/18139459/find-nsdate-in-sorted-nsarray">Find NSDate in sorted NSArray</a></p> <p>I want to know which date in the array is nearest in time to my reference date.</p> <p>I must do this frequently. The following works but is slow - how can I speed things up?</p> <pre><code>// Get the XYZ data nearest to the passed time - (eciXYZ)eciDataForTime:(NSDate*)time { // Iterate our list and find the nearest time float nearestTime = 86400; // Maximum size of dataset ( 2 days ) int index = 0; // Track the index int smallestDifferenceIndex = index; // Track the index with the smallest index NSDate *lastListDate; // Track the closest list date for ( index = 0 ; index &lt; [self.time count]-1 ; index++ ) { NSDate *listDate = [self.time objectAtIndex:index]; // Get the date - Time is an NSMutableArray of NSDates // NSTimeInterval is specified in seconds; it yields sub-millisecond precision over a range of 10,000 years. NSTimeInterval timeDifferenceBetweenDates = [listDate timeIntervalSinceDate:time]; if ( timeDifferenceBetweenDates &lt; nearestTime &amp;&amp; timeDifferenceBetweenDates &gt; 0 ) { nearestTime = timeDifferenceBetweenDates; // Update the tracker smallestDifferenceIndex = index; // Update the smallest difference tracker lastListDate = listDate; // Capture the closest date match //NSLog(@"Time: %f %@",timeDifferenceBetweenDates,listDate); } } </code></pre>
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