All language subtitles for 3. [Dart] Lists

All right.
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So in this lesson, we're going to do a deep dive on Dart lists. And we've already seen that we can create
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a list just as you would create a shopping list, by adding some items to the list and they each go in,
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in order.
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So for example in this case, if I was creating a guest list for my upcoming party, then as I add names
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to the list they will go in, in order.
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And remember that when we're dealing with computers, they always start counting from zero.
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So that means that the first item is actually going to be the zeroth item in the list, and then the order
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goes on logically.
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So when you're picking items from the list you would refer to them by their index.
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So in this case Angela is at index 0,
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and Katie is at index 2. And it's a little bit counterintuitive because of the fact that the list starts
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from 0.
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So if we were to pick the third from the list, it's actually not 1 2 3, but it's actually this
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one. We can see how this works using DartPad.
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Now DartPad actually allows you to share code that you've created.
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So I want to share with you a little bit of code that I made earlier on to make this exercise a little
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bit easier for you
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so you don't have to copy out all the names. And the way that you would share a DartPad is you would
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write some code, and create aGitHub gist. Now a GitHub gist, unlike your GitHub repos,
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these are just a single code file, and it allows you to share snippets of code around very very easily
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and it's completely free to create and to use.
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So I've created this just under my account. And now when I'm viewing this gist, I can see that it's under
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this address.
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So if I copy everything that comes after my username and a forward slash, then I can paste it at the
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end of the dartpad.dartlang.org website.
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So I'm going to add a forward slash and paste that in here.
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And now when I hit enter, it will load up that's just as a Dart file inside DartPad.
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So I will show you this URL, so that when you go to it, this is exactly what you will see.
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So we can work on the same file together.
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Once you're here, then you'll notice that I've already created a list of strings called myList.
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And inside the list, I've created it with some starting pieces of data.
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So I've got four names in here that matches exactly what you saw earlier in the slides.
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Now if I wanted to pick out the third item from my list, I would simply say my list, that's referring
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to this variable called myList,
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and then I would add a set of square brackets and inside I can provide an integer, so a whole number,
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and this can refer to the index of the item that I want to pick out of the list.
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So if I put the number 3 in here, then this is now going to be equal to the item inside my list
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that is at the third position.
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So zero, one, two, three.
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So this should now equal Jack.
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And we can confirm this by simply printing it into the console.
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So I'm going to wrap a print statement around it, and hit run.
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And you can see in here we're going to get Jack printed.
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So it's pulled out
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the third item out of the list.
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You can also try and get the index by providing the piece of data.
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So for example, if I was looking for Katie in my list, then I would get back that it's at index number
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2. And we can do this by simply saying myList.indexOf, and we have to provide the string that
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we're looking for which in this case is Katie.
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And it has to be spelt exactly the same way in terms of capitalization. And now when we print this instead,
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so let's comment that out and let's wrap a print statement around this that we've just created.
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Now when I hit run, we're going to get 2 in the console, because this is equal to 2. Now as we saw earlier,
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you can also add it to the list by simply using the .add, and then inside the parentheses you would
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provide whatever it is that you want to add.
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And remember that when you're adding to the list, the new item always goes at the end of the list not
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at the beginning or some random. So in this case, if we were to go ahead and comment this out, and I'm
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going to write myList.add and the thing that I'm going to add is a another person onto my guest
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list.
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And now if I print myList, then we can see what it now looks like all right.
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So let's run our code, and we can see that our list consists of Angela, James, Katie, Jack and Ben. And the
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console is very helpfully telling you that this is a list by showing you the data inside a square bracket.
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So we can see that whenever we use add, it always adds our data right to the end
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right?
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But if you wanted to add your data somewhere in between,
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there's also a way to do this. You can actually insert a piece of data into the list and push everything
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that came afterwards to the next index.
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So in this case, Ben came in here and it was inserted into position 2 which displaced the previous item
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that was at position 2 to position 3. And the way that we would do this is we would write instead
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of myList.add, we would instead say myList.insert. And we have to provide a index,
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so where do we want to insert it in the in the index of our list? And also what is it that we want to
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insert?
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So Ben is going to be promoted to position 2 and of course the string that we want to insert, is the
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name Ben.
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So now if we had run, you can see that previously Ben got added at the end,
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now Ben is going to show up at position 2. Remember our list starts from 0, 1, 2.
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Now there's a whole lot of other things that you can do with lists and you can discover some of those
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even as you're typing.
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So when you write myList. you can see that DartPad is already suggesting all of these things
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I can do using lists.
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For example, I can try and get the first item in my list by simply writing myList.first.
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And I could also get the last item in the list by writing .last.
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And there's also loads of other things I can do like sort my list, or remove things in my list.
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And if you want to learn more about all of these things that you can do with Dart lists, I'll add a link
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to this
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URL, which is a page on the Dart language guide where it talks about lists and all of the things
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that you can do using Dart lists in more detail.
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So I recommend browsing through this website and seeing, at a glance, what are the things that you can
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do with lists.
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But there's no need to memorize them because once you come across a actual use case, when you find the
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need to use a particular functionality of the list, then you can simply search for it and you'll come
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across either a piece of documentation like this or a post on Stack Overflow where you'll be able to
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use it as you need to. That's all on list. In the next lesson,
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we're going to get back to coding up our app and we're going to start displaying some questions.