Question

Let’s say you have a float 5.9476386 and an NSArray with the floats 1,4,8,12,… stored in ascending order.

NSArray *centers = [NSArray arrayWithObjects:
                     [NSNumber numberWithDouble:1],
                     [NSNumber numberWithDouble:4],
                     [NSNumber numberWithDouble:8],
                     [NSNumber numberWithDouble:12],
                     ...
                     nil];

I want a new float that rounds the number to the closest number in the array.
So in this case the new float wil be 4 because 4 is the closest of the numbers of the array to 5.9476386.

How can i do this? I’m working in Objective-C/Cocoa

Answer 1

Assuming your array is sorted in ascending order

 for ( int j=0; j< [myArray count]; j++ ) {
     float current = [((NSNumber *)[myArray objectAtIndex: j ]) floatValue];
     if ( current > myFloatNumber ) {
         if ( j==0 ) { return current;}  // 

         float prev = [((NSNumber *)[myArray objectAtIndex: j-1 ]) floatValue];

         if ( fabs(prev-myFloatNumber) > fabs(current-myFloatNumber) ) {
            return current;
         } else {
            return prev;
         }
     }
 }