How do I count the objects in an NSArray that have a certain value?

Question

I have an NSArray populated with 0's and 1's. How can I return the number of 0's in the array?

Thanks!

Answer 1

Declare a counter, set it to 0, loop through the array and if the element is 0, increment the counter.

Answer 2

Iterate through the array and count the things you're looking for.

Assuming you have an NSArray populated with NSNumbers:

NSArray* array = ... ; // populate array
NSUInteger count = 0;
for (NSNumber* number in array)
{
    if ([number intValue] == 0)
    {
        count++;
    }
}

Answer 3

A little perverted solution :)

NSUInteger zeros_count(NSArray *array) {
  NSUInteger sum = 0;
  for (NSNumber *number in array)
    sum += [number intValue];
  return [array count] - sum;
}

Answer 4

Depending on your application, you might consider using an NSCountedSet.

When it comes time to get the count of a certain type of object, you can just use the countForObject: instance method.

Probably a little too heavy for your current problem, but may be useful for others looking for similar solution.

Answer 5

NSArray* array = [[NSArray alloc] ...]; ; // put data into the array

NSUInteger arrayWithValue = 0;

for (NSNumber* number in array)

{

if ([number intValue] == NUMBERYOUARELOOKINGFOR)

    {
        count++;
    }
}

Answer 6

KeyValueCoding

int count = [array count] - [[array valueForKeyPath:@"@sum.intValue"] intValue];