How do I retrieve each value from an array and add it to the value of my variable 'sum'? Using counter as an index value

The idea is to use a while loop and run the loop as long as there are numbers in the array. With every iteration, we would receive the value from the numbers array, add its value to sum and then increment the counter.

This approach is based on two ideas:

• You get an element of an array by providing its index: numbers[index]
• The while loop runs only if there are still numbers in the array. We can get the number of elements an array contains via count

So, a while loop runs as long as a condition is true. In our case, the condition would be

// If counter is less than the number of elements in the numbers array, this is going to be true
counter < numbers.count

Remember, array indices are zero based, that is the index of the first element is 0. count will return the number of elements in an array, so if there are 4 elements, the index of the last element is 3.

Therefore, if you want to run a while loop as long as there are numbers in the array

// If counter is less than the number of elements in the numbers array, this is going to be true
while counter < numbers.count {
  counter++
}

See how we increment the value of counter every time the loop runs? This way we make sure it runs just as often as there are elements in numbers and it won't run infinitely.

The only thing left to do now is getting the value for each element. As mentioned before, we can get an element of an array by it's index. As we are incrementing counterone by one, we can use counter to get each element: numbers[counter]

So the final code would look like this:

let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0

while counter < numbers.count {
  sum += numbers[counter]
  counter++
}

Hope that helped :)