AKMA’s Random Thoughts

Ha! Liveblogging will be th erule of teh day. I am not wireless, however, so I claim dibbs on the outlet in the west wall!!!

Does one have to be marinaded before a technological grilling? Is this a pot-luck? What a good idea...

Truly sorry I won't be there for this one, AKMA. It's been a great series, for which you (and Seabury) should be commended widely.

Let's see an example by converting our favoriteNumber variable from a stack variable to a heap variable. The first thing we'll do is find the project we've been working on and open it up in Project Builder. In the file, we'll start right at the top and work our way down. Under the line:

This will allow us to use a few functions we didn't have access to before. These lines are still a mystery for now, but we'll explain them soon. Now we'll start working within the main function, where favoriteNumber is declared and used. The first thing we need to do is change how we declare the variable. Instead of

Note first that favoriteNumbers type changed. Instead of our familiar int, we're now using int*. The asterisk here is an operator, which is often called the "star operator". You will remember that we also use an asterisk as a sign for multiplication. The positioning of the asterisk changes its meaning. This operator effectively means "this is a pointer". Here it says that favoriteNumber will be not an int but a pointer to an int. And instead of simply going on to say what we're putting in that int, we have to take an extra step and create the space, which is what does. This function takes an argument that specifies how much space you need and then returns a pointer to that space. We've passed it the result of another function, , which we pass int, a type. In reality, is a macro, but for now we don't have to care: all we need to know is that it tells us the size of whatever we gave it, in this case an int. So when is done, it gives us an address in the heap where we can put an integer. It is important to remember that the data is stored in the heap, while the address of that data is stored in a pointer on the stack.

That gives us a pretty good starting point to understand a lot more about variables, and that's what we'll be examining next lesson. Those new variable types I promised last lesson will finally make an appearance, and we'll examine a few concepts that we'll use to organize our data into more meaningful structures, a sort of precursor to the objects that Cocoa works with. And we'll delve a little bit more into the fun things we can do by looking at those ever-present bits in a few new ways.

But some variables are immortal. These variables are declared outside of blocks, outside of functions. Since they don't have a block to exist in they are called global variables (as opposed to local variables), because they exist in all blocks, everywhere, and they never go out of scope. Although powerful, these kinds of variables are generally frowned upon because they encourage bad program design.

This will allow us to use a few functions we didn't have access to before. These lines are still a mystery for now, but we'll explain them soon. Now we'll start working within the main function, where favoriteNumber is declared and used. The first thing we need to do is change how we declare the variable. Instead of