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‫Welcome back.

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‫In this video we are going to look into nobles.

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‫And nobles are a concept that you see in other programming languages.

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‫For example, Swift uses them quite extensively and there they are called options.

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‫So they are variables that can have a value or they don't have a value.

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‫So there are two options, right?

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‫So either something has a value or does not have a value, and usually that's null or not.

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‫So let's create some.

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‫And by the way, it's a data type, so the data type can be empty or not.

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‫And usually that's like Nullarbor as you can see here and Nullarbor of type int 32 for example.

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‫So that's generally how you write, how you would write it.

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‫That would be a Nullarbor in 32.

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‫So evaluated can have values from -2 billion roughly up to plus 2 billion.

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‫So let's go ahead and create them.

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‫So in order to create a novel, you just add a question mark after the data type.

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‫So if you want to have a integer Nullarbor as I've just written, you will just use end question mark

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‫and I'm just going to call that number one and it's going to be null.

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‫Let's create another one that I'm calling NOM two and set that to NULL.

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‫And as you can see, we get an error here so it's complaining it says cannot convert null to int because

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‫it is not or a non unknowable value type.

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‫So you cannot assign null to an integer.

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‫That's what you say C here, but you can assign null to a global integer, which we've done in line

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‫nine.

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‫All right, so let's create another one and it will be num two and it will be 1337 1337.

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‫That's how you would go ahead and create an elbow.

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‫When you see it's either null or it has a value.

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‫The same goes for doubles.

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‫So double question mark.

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‫Number three is new double and question mark like that.

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‫So that's also how you can assign a multiple double.

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‫So this one will be empty or here num four is 3.14157.

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‫So that's PI.

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‫And the same goes for Booleans.

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‫So it's a multiple bool and I'm going to say Boo Vol is a new bool

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‫question mark like that.

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‫So now let's check it out.

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‫Let's just display that on the screen and see what we get.

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‫So see w our global numbers are and we're going to use zero one.

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‫Two and three.

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‫And that will be number one.

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‫Numb to numb.

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‫Three and four.

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‫And now, of course, it's complaining because I need to end my string here.

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‫All right.

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‫And let's also display our bool.

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‫So c w the multiple boolean value is and bool vol.

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‫Now okeydokey.

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‫So let's try that control f five.

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‫And our knowable numbers are, as you can see, nothing.

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‫So it's not even an empty space.

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‫It's just nothing.

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‫One, three, three, seven, nothing and 31415, seven.

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‫And the null boolean value is nothing.

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‫So as you can see, it can be nothing and it's not complaining.

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‫So even though there is no value in there, it's still fine.

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‫It's not crashing our program or stuff like that.

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‫If you would try to do the same thing with an integer which is not knowable, so let's create an integer

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‫called number five and let's just do it like that.

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‫So we didn't initialize it and it's also empty, right?

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‫So there is no value in there if I try to access that one like that.

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‫And I'm going to use number five here.

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‫Let's check that out.

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‫Control the five.

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‫And as you can see, we have build errors so we can't even stop that because it says use of unassigned

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‫local variable number five.

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‫So that's the whole point about that.

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‫You create a variable that can be empty or it cannot be empty and that's totally fine with the program.

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‫It won't crash.

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‫And why would you use that?

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‫What would be the idea behind Noble's?

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‫Well, imagine you have a program which works with loads of data, so it has user data and it gets it

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‫from the database.

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‫And for some values or for some columns, there are simply no entries.

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‫So let's say we have usernames.

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‫We have personal name or first name, last name, then we have birthday and so forth.

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‫All of those information can be stored within our database, but for most users we only have the username.

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‫We don't have their first name, last name.

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‫We don't have the password or email address, nothing like that.

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‫We only have the username but we still want our program to work correctly.

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‫So we will just use nobles which are fine.

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‫If there is no value.

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‫They will not make our program crash.

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‫So let's make it very, very generic example of that.

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‫And I'm going to use a bool here, which will be a multiple bool and I'm going to call it Ismael and

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‫I'm going to set it to NULL.

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‫And in here I'm going to just check is mail, is it null or actually is it true?

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‫So if it's true, let's write something like user is mail then else if it's mail is false, we're going

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‫to say something like user is female.

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‫And then finally else we just say something like no gender chosen or maybe something like no gender

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‫could be found or something like that, and that we are.

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‫So now you can go ahead and use that kind of approach.

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‫Right.

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‫And here I'm going to put it in the next line.

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‫And if we run that well, of course, we get no gender chosen.

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‫And in my case, my program will shut down straight away after it says that.

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‫And I still have.

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‫An error somewhere and.

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‫Well, how would I figure it out?

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‫Well, it's this one here.

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‫So I have this for still in my text and it's trying to access it.

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‫But there is something missing, so that's why it doesn't work.

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‫All right, now we can try it again.

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‫Control F five and we are our knowable numbers are.

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‫That's totally fine.

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‫And then here, no gender chosen.

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‫All right.

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‫That's all good and stuff.

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‫But what if you want to convert a gullible into a non gullible type?

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‫Well, let's go ahead and try that.

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‫Let's create a gullible double here.

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‫Let's call it number five and it's going to be 13.1 and then double or actually let's call it number

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‫six, because we have this number five here, which we never used, but I'm just going to leave it there.

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‫It's not hurting anyone.

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‫So number seven is going to be null.

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‫So how do I convert those into a non knowledgeable type and I'm going to create a NUM eight which will

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‫be a non knowable double.

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‫So it's a general double, right.

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‫It can't be null or we cannot assign null to it.

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‫And now we just check if num six equals null then num eight will be 0.0.

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‫And else we're just going to say num eight should be num num six six.

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‫But there we have the problem because as you can see that we entered that I cannot just assign it it

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‫says cannot implicitly convert type double question mark to double and explicit conversion exists.

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‫So are you missing a cast?

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‫And that's what we need to do.

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‫So we need to cast it into a double because we need we know if it's not now, then num six internally

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‫is a double, so it contains a double value.

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‫So I'm just going to use that and assign that to NUM eight so we can just go ahead and display that

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‫value of NUM eight is num eight.

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‫So let's start out with control f five.

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‫And as you can see, value of NUM eight is 13.1.

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‫So the casting, the explicit conversion worked.

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‫There is, however, a faster way to do that.

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‫So as you can see, it was quite some effort.

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‫We needed this.

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‫If an LS there is the null coalescing operator that we can use for that.

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‫So we can just say num eight is equal to num six.

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‫Question mark.

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‫Question mark 8.53 for example.

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‫So if num six is empty, then go ahead and add or enter 8.53 and if not, then do something else.

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‫So what I'm going to do is I'm going to add another line and I'm going to write something like value

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‫of num eight is and actually let's just copy that because we need that twice and I don't want to type

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‫so much so that we are now let's go ahead and try that again.

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‫Let's see the difference.

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‫And as you can see, value of NUM eight is 13.1 value of num eight is 13.1 and value of NUM eight is

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‫8.53.

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‫So what happened here?

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‫What was ignored here in line 50 because it said well, it was well, I assigned 8.53 to it.

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‫But as it seems now, I'm six.

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‫Had a value and it was taken.

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‫So as six had a value, just took a 13.1 and as number seven didn't have a value, num eight now is

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‫8.53 because if we look at it, num seven is null, so we assign a different value to it.

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‫So that's called I'm just going to.

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‫Copy it over for you.

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‫The null collapsing operator.

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‫Double question mark.

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‫So if you want to convert from a normal to a non movable type, then you can use the null coalescing

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‫operator.