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iOS Objective-C Basics (Retired) Pointers and Memory Array Size and Length

Do not understand what the error message means. It tells me I have the correct string but not the correct format.

Isn't %s the correct formatting for a string? When I do this in Xcode it compiles and gives me "Array real_numbers is 20 bytes." Why does the Treehouse console say it is wrong? And what would be correct?

array_length.mm
float real_numbers[5];
printf("Array %s is %ld bytes.\n", "real_numbers", sizeof(real_numbers));

1 Answer

Hi Abbey,

I feel like the message that the challenge is giving you is confusing. The issue isn't that %s is the wrong formatter - that is the correct one to use with a string - it is that the string within the quotes is not formatted as TH expects it to be...that's confusing, I know, so here you go:

When you check your work TH sees this - literally:

"Array %s is %ld bytes."

When what it is expecting - literally is:

"Array real_numbers is %ld bytes."

If you replace your %s with "real_numbers" and remove "real_numbers" as the second argument you're sending to printf, your code will pass - as such:

float real_numbers[5];
printf("Array real_numbers is %ld bytes.", sizeof(real_numbers));

I'm not sure if it is a bug or just a poorly 'formatted' question and response. I hope this helps you out.

Ok well I feel a bit better because that is actually what I gave it as my answer the first time however THIS is the error message it gave me for that:

Make sure you are calling printf and passing a string (not an NSString) and "real_numbers" as the parameters. The correct format option is '%ld'.

Which as you can imagine confused me no end and so I continued to try various combos.

But now I realize for whatever reason when I did it the first time I wrote &ld not %ld. Perhaps my brain is done for the evening. :)