1
00:00:05,940 --> 00:00:12,480
The option enum is important because it allows us to either allow a value to be something or it could

2
00:00:12,480 --> 00:00:13,080
be nothing.

3
00:00:14,200 --> 00:00:21,580
The nothing aspect is comparable to Nohl and other languages, whereas Rust does not have the Noel feature,

4
00:00:21,640 --> 00:00:24,790
it just uses none inside the option in them.

5
00:00:24,790 --> 00:00:27,850
So let's look to see how the option enum is set up.

6
00:00:27,850 --> 00:00:35,770
So we have enum option of a generic DT, which we will learn about in the next section.

7
00:00:36,100 --> 00:00:45,910
And then inside this enum we have none and then we have some T and that's all there is to it.

8
00:00:45,910 --> 00:00:47,230
To the option enum.

9
00:00:47,560 --> 00:00:48,250
The.

10
00:00:49,160 --> 00:00:53,000
T means it is generic, which as I said, we will cover in the next section.

11
00:00:53,000 --> 00:00:57,500
But to simply put it, it can hold a piece of data of any type.

12
00:00:57,740 --> 00:01:03,890
You do not have to do anything in order to use this option in them as it is already available inside

13
00:01:03,890 --> 00:01:05,120
the scope for us already.

14
00:01:05,120 --> 00:01:07,070
So I can delete all of this.

15
00:01:08,750 --> 00:01:12,590
And then here we can say let some number.

16
00:01:14,390 --> 00:01:17,060
Equals some five.

17
00:01:19,000 --> 00:01:24,220
And just to make it clean, clean it up, let some string.

18
00:01:24,220 --> 00:01:30,220
And this is going to be a reference to a string slice, but a string.

19
00:01:31,630 --> 00:01:42,430
And then we can say let nothing equal of an option and we'll specify that it's also an eight.

20
00:01:44,250 --> 00:01:47,910
Equals none.

21
00:01:48,360 --> 00:01:53,430
So all of these are valid and it is important to know that option.

22
00:01:53,430 --> 00:01:59,460
T So what we have here, this is the same thing as saying we're declaring the type.

23
00:01:59,460 --> 00:02:07,020
But behind the scenes, before we say it's an idea, it is option T whereas.

24
00:02:09,410 --> 00:02:15,560
Let X equals five is equal to an I 32.

25
00:02:15,590 --> 00:02:19,280
So I guess just to really clarify this, let's make that an I 32.

26
00:02:21,870 --> 00:02:29,970
These two when we declare option I 32 and then we declare a variable to have five, which is I 32 by

27
00:02:29,970 --> 00:02:30,690
default.

28
00:02:30,720 --> 00:02:31,950
These are not the same.

29
00:02:32,730 --> 00:02:43,110
So we can show this by saying let x of I 32 equal to five, and then it will say Let Y.

30
00:02:44,660 --> 00:02:51,320
Of Option I 32 also equal to five.

31
00:02:53,420 --> 00:02:58,990
That helps if I put the some keyword.

32
00:03:01,040 --> 00:03:10,370
So now if we try to add these let some equals to x plus Y, we see we get an error and it says we cannot

33
00:03:10,370 --> 00:03:13,850
add option of EI 32 to EI 32.

34
00:03:14,530 --> 00:03:21,760
So you would have to convert the option of I 32 to an I 32 before we could perform this operation.

35
00:03:22,540 --> 00:03:29,170
So to wrap up what an option enum is and when we want to use it, we would want some code that would

36
00:03:29,170 --> 00:03:33,130
run, but only when we have some key.

37
00:03:33,730 --> 00:03:38,830
And then that code uses the inner T and remember, PT is the data type.

38
00:03:39,400 --> 00:03:43,150
We would also want code to handle the case of when we have none.

39
00:03:44,340 --> 00:03:49,230
So we want code that can be able to handle something or nothing.

40
00:03:49,350 --> 00:03:55,080
Well, luckily for us, we had Rust gives us the match expression, which is a control flow construct

41
00:03:55,080 --> 00:03:59,000
that does exactly this when we use it with enemies.

42
00:03:59,010 --> 00:04:03,690
So let's take a look at how that match statement works in the next lecture.