Still confused about while, loops

Question

Trying to figure out how to do it using right order and codes ...
Challenge Task 2 of 2
Now that we have the while loop set up, it's time to compute the sum!
Using the value of counter as an index value, retrieve each value from the array and add it to the value of sum.
For example: sum = sum + newValue. Or you could use the compound addition operator sum += newValue where newValue is the value retrieved from the array.
/Users/mattconway/Desktop/Screen Shot 2016-01-13 at 6.50.22 PM.png
```while.swift
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0
// Enter your code below
while counter < numbers.count { counter++ }
var newValue = sum += newValue
while index < newValue.count {
  print(newValue[index])
  index++
  }
```

Jhoan Arango · Accepted Answer

Hello :
A while loop basically means "While this condition is true, then continue until is false". 
In this challenge we have an array to iterate through.
```swift
let numbers = [2,8,1,16,4,3,9]
```
So now we have to create a condition to be able to use this while loop. 
```swift
let numbers = [2,8,1,16,4,3,9]
var sum = 0 // We will use this to add all the numbers inside the array
var counter = 0 // We will use this for the condition, and as the index for the array
```
Now let's create that loop...
```swift
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0
// Loop
while counter < numbers.count {
counter++
}
/* 
This is saying "While counter is less then the 
amount of items in the array then continue, 
and add one more to counter"
*/
```
Now we finish the loop by retrieving an item from the array, and adding it to the sum variable.
```swift
let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0
// Loop
while counter < numbers.count {
sum += numbers[counter]
counter++
}
```
So basically what we are doing is grabbing one item from the array as the loop goes around the first time, and adding it to the sum variable, then we update the counter by adding to it. So now sum is 1, and this will help us with the next item in the array by using counter as the index. Once the condition becomes false, which it will after we have no more items in the array, the loop will stop. 
Hope this helps you understand while loops a bit more.

Reagen Rahardjo · Answer

Hi, I tried to run the program on XCODE but i got this message back Untitled Page[30758] : CGContextSaveGState: invalid context 0x0. If you want to see the backtrace, please set CGCONTEXTSHOW_BACKTRACE environmental variable. is it an error?

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Matt Conway

Matt Conway

Still confused about while, loops

2 Answers

Jhoan Arango

Jhoan Arango

Reagen Rahardjo

Reagen Rahardjo