Mac Programming Lesson 2 part 1
Hey guys, this is Mac Kids, and on with Mac programming lesson two. So, this programming lesson isn't going to be about polishing your application or gooey stuff; it's going to be about understanding. Because basically, I watched a bunch of Partners videos and professional YouTube videos on how to program, and it seemed like after watching their videos, you might actually be able to make a good application all by yourself. But you may not necessarily truly understand what's going on.
Understanding what's going on in things like C and Objective-C is something that takes a long time. I've been doing C for almost a year, and just a month ago, I actually started to understand what I'm actually doing. By now, I pretty much get what's going on. And so, as I'm not the best teacher ever, I'm going to try my best to pass the information along. But you may not catch the drift, so this is hard.
I'm going to be using a terminal application to get you guys to really understand what variables are and what pointers are. Because in, say, um, Java, it's pretty easy to understand; there are no stars, there's no, like, nothing. A variable is just a variable, and you can use dots to do stuff with it. But with this, I have to teach you guys what you're actually doing because in Java there is no like, what you're actually doing, because you don't have that kind of power.
So, I'm going to make a new project, and I'm going to go under command line utility. I'm going to click Foundation tool. I'm going to call it, um, plain old learning, just to represent we're just learning stuff; there's nothing new. And so, you'll notice under Source, there's one M file, which is plain old learning.m. This is where we're going to put our stuff.
So, let's start from the ground up. Right here is a C function. This is how you normally would declare a function in C; it's variable type space, you know, thingy space, left parentheses, parameters, right parentheses, and at the top there's an import. What this import does is it uses the Foundation Library, which has things like NS3 ring in it.
So now from there, you might notice that NSLog takes something that starts with at, then two quotes, and inside of that quotes can be whatever you want. Whenever you put an at before quotes, it knows that you want to put an NSString there, and it converts what's inside of those quotes to be an NSString.
People didn't understand at is like a magic character in Objective-C, especially this version of Objective-C, that will tell everything basically that you want to make an NSString or you're going to synthesize something. It's really an important thing to notice; if you get rid of the at, then it thinks you're just giving it a character array. Because this is, of course, C, and in C, you declare a character array with quotes, so that's not exactly how this is going to roll.
I need to get rid of this NSLog; we're going to ignore that for now, and we're just going to type in between this NSAutoreleasePool and pool drain. So right here, first of all, you know when you're declaring a string in Objective-C, the class name or variable name is NSString. Then you do a space and then normally you do the variable name in Java, but you know, to do a star somewhere between the variable name and the, um, variable type.
So I'm going to make an NSString *foo, and you know we have to do that star there, but you're not exactly sure why. The star means that I'm not going to specifically own foo; all foo is going to be is a little number that represents some place in my RAM, in my memory. So foo in this case, since it's a 32-bit application, will be four bytes, and that's four characters or four numbers.
So foo is going to be four numbers, um, and that tells the computer where in memory all of the memory can be represented by four different numbers. So foo is just going to point to something else. So when we say foo =, we're just going to be changing the four numbers that it is, not what's actually in it.
So say I do NSString *foo =; then I'll do left bracket, left bracket, NSString alloc, init. Now, first of all, NSString alloc means we're going to make a new pl...