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iOS Objective-C Basics Scope and Loops Review Scope and Loops

Posted by Brandon Oree
Brandon Oree
1,585 Points

Challenge Task 2 of 2, for looping (Obj-C)

I feel my code is mostly correct. I've even debugged this in Xcode, mathTotal starts with 5 and ends at 25. What am I doing wrong?

variable_assignment.mm 
int mathTotal;
bool isComplete;

for (mathTotal = 5; mathTotal < 25; mathTotal++)
{
  isComplete = FALSE;
}

1 Answer

Jason Anders
MOD
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

Hey Brandon,

There are a few errors happening here:

  1. For loops use temporary variables (I always use i) to iterate through the loop. The variable mathTotal (an Integer) cannot be used in both the loop and as a variable outside of the loop. This is the variable that will hold the cumulative total as the for loop iterates and adds to the variable.

  2. Right now your loop will stop at 24 (because it is stating less than 25, which does not include 25). The challenge specifically asks you to keep the 25 in there, so you will need "less than OR equal to).

  3. Your boolean value for isComplete needs to be outside of the loop block, as this will be assigned only when the loop is done.

  4. isComplete needs to be set to "true" not "FALSE" after the loop.

  5. The incrementing code for mathTotal is missing. This needs to be inside of the loop, so with each iteration of the loop, the new value for i gets added to the running total of mathTotal.

Below is the completed and corrected code for your reference. I hope it makes sense.

int mathTotal;
bool isComplete;

for (int i = 5; i <= 25; i++) {
  mathTotal += i;
}

isComplete = true;

Keep Coding! :)

:dizzy:

Brandon Oree
Brandon Oree
1,585 Points

Jason, I've looked through your code a few times and, though I know it's right, there are a few things that still puzzle me. I'll review the videos again, and continue studying your code, until I completely understand looping. Thank you for the assistance!

Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

I'll see if I can help a bit.

You declare the int i = 5. This tells the loop that you want to use the temporary variable i to keep count, and you want it to start at 5. So, the start of the loop, i = 5.

Then the i <= 25 checks the condition. In this case, it is checking to see if i is equal to or less than 25. It is, so the loop says to add 1 to the previous value of i and execute the code block.

The code block executes and add the value of i to the variable mathTotal. The loop now starts over with i now equal to 6. It goes through again. Executes the code block and adds the new value of i to the existing value of mathTotal.

It will do this until the value of i hits 26, which is now no longer less than or equal to 25. It's now that the code block will not execute, and will bounce out of the loop. The code isComplete = true; now runs (because it is outside of the loop and the loop has been completed).

Reviewing is always a good idea, I often review and/or rewatch videos. It's best to have a good understanding before moving on.

Have a look at TutorialsPoint or just Google "for loop in objective-c". Honestly, you could also look at any JavaScript tutorials on for loops as they are pretty much exactly the same as Objective-C. Sometimes all one needs is an explanation given in a different way for it to click. :)

Brandon Oree
Brandon Oree
1,585 Points

I understand completely now. I think my confusion was stemming mostly from my unfamiliarity with the concept, but seeing your code and comparing what worked to what didn't, and why, helped. I hope I didn't bog down much of your time.