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Are you ready for another Swift Deep Dive? In this lesson,
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I want to talk about Arrays and Arrays are essentially just collections of items,
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so whereas variables, you have a name that's associated with a single piece of data. What do you do if
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you have lots of data that are somehow associated with each other like a basket of apples?
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Well, that is kind of like an array of apples, right?
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Creating an Array is pretty simple.
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We use these square brackets. And inside the brackets, we drop in all the items that we want to put into
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the same collection or the same Array, and we separate them by commas.
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So we now have an Array of names and we have three items in our Array.
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Now, when we want to access items from an array, then we can use another set of square brackets and we
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tag it on at the end of the Array. And inside the square brackets,
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that X is a number that refers to the position of the item that we want to retrieve from the Array.
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And if you remember from previous lessons, we said that programmers love counting from zero.
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So the first item that Angela is at position 0, Jack is at position 1, and Philip is at position 2.
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So if we replace the X with 0, 1, or 2, then we will be able to retrieve a single item out of our Array
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depending on which position we specified as x.
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So just as we can store other pieces of data, such as numbers or text in a variable, an array is just
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like any other piece of data and it, too, can be stored inside a Variable.
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Let's say that we had a Variable code friends, we can assign it the value of our Array.
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So now we want to access this Array, we can refer to that reference code friends.
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And, again, when we're accessing items from an Array that's been stored inside a Variable,
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it's exactly the same thing.
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Whereas before we had a straight up Array and we tagged on at the end a set of square brackets and a
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number that referred to the position of the item that we wanted to access.
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Well, if we had the array stored in a variable, it would look like this.
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We would refer to the name of the array and then we would, again, tag a set of square brackets at the
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end, and the X refers to the position of the item that we're interested in from the Array.
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The easiest way to think about an array is to imagine you had a spreadsheet where you only have a single
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column.
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For example, here, I have an array of famous people and I've got a whole bunch of names in my Array and
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they are numbered.
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So in the case of a spreadsheet, they're numbered from 1 to 10.
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But if this was an Array, then this would be at position 0, 1, 2, et cetera. It's essentially a single column
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with a whole bunch of data in it and each piece of data has a position associated with it.
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So that's just another way to think about Arrays.
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And if you've worked with spreadsheet delight, then this might be a really easy way for you to understand
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and visualize Arrays.
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So I've got a challenge question for you.
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Why did the programmer quit his job?
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Well, because he didn't get a raise, of course.
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Now, that's not the actual programming challenge.
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Instead, you're going to be writing some code to test your knowledge on Arrays.
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Now, the Array that I'm going to create is gonna be stored inside a Variable called numbers and I'm gonna
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set it to equal a bunch of numbers.
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So that's a 45. 73, 195, and 53.
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So I have an array of four numbers.
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Again, if you need to refer to how Arrays are structured, namely what kind of bracket does it use,
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and how do you separate each of the values in it,
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then you can take a look at the Swift Cheat Sheet, and remind yourself of how you create Variables and
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how you create Arrays.
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Now, I'm going to create another Variable called computedNumbers and I want you to write some code, so
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that when you print the computed numbers, the end result that you should see down here is the first number
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multiplied by the second, as the first value,
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and then it's the second number multiplied by the third, and finally, it's the third multiplied by the fourth.
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So let's say we had an array of 1, 2, 3, and 4, then the outcome that should be printed is 1 times 2 equals
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2, 2 times 3 is 6, and 3 times 4 is 12.
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So that would be the desired outcome. But instead, you're going to be working with these large numbers.
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And I don't want you to actually take a calculator and work out what is 45 times 73, and then what's 73
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times 195.
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And in fact, I don't even want you to write any code that includes those numbers 45, 73, 195, and 53.
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I want you to use purely just your knowledge on how to pull items out of the Array and use the Swift
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program to calculate these values for you.
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Now, in order to complete this challenge, you'll need to know that to multiply a number, say, 1 times 2,
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in Swift, It's done using the asterisk symbol.
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So if I print 1 * 2, and let me just coming out the code that's currently incomplete which is giving
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us some errors, then once my code runs you'll see 2, or 5 times 2 which should be 10.
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So multiply the value at position 0 by the value at position 1, and then the 1 position 1 by the one
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at position 2, and you should end up with an Array of computed numbers which is going to be printed and
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it should have three items in that Array.
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And I'll see you on the other side. Good luck!