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Hello and welcome back in this lesson you're going to talk about swift optionals swift optionals might

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seem a little bit confusing at the beginning.

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So I'm going to try to simplify it as much as I can in this lesson.

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So if the optionals has only one meaning to make sure that your valuables have a value when you use

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them.

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So essentially it's a way for us to make sure that you don't act as a value that doesn't have anything

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in it.

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You don't access any value which is going to cause your application to crash.

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So let's go ahead into export and see how we could actually use them.

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I'm going to go to school and I'm going to start a new Actually this time I'm going to start a new command

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line tool.

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I'm going to say command line tool strafed and then when I call it my option is to

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and my optional tours I'm going to produce three different variables.

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I'm not talking about all three of them.

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One of them I'm going to call it the optional string.

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And that's going to be a strong question mark.

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The other one I'm going to call it the VAR non optional string.

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It is of the type of string that you keep the same formatting and it says hello.

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And then the last one is going to be there.

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On the wrap string.

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And that's the type of string.

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So I want to spend a few seconds having a look at this.

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And then when I explain what they mean.

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So now let's try to understand what do these three things mean an optional a string with a string questionmark

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means this value could be nil.

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It's possible that it doesn't have anything inside it.

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So whenever you want to use it and we know the value exists we have to actually access it by saying

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something for instance like optional a string and we have to force it.

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We have to say now we know the value exists.

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Obviously this is not going to print nilla for us because it is not there but for us it means that it's

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likely you could be in in a few minutes.

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I will show you how we go about doing this in a safe way because this is really not a very safe way

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of forcing it because for instance if you set this value was my user name and it is nil because user

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may not have entered the username in the text field.

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And then if you had a function hypothetical function that says like innovate the user name and you entered

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this in here.

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Then obviously this is going to crash because it is going to say well you're trying to log in with something

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that doesn't exist all you're trying to do something like luggin with Ned.

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So I'll show you in a minute how we go about being safe with it.

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However whenever you have an optional string it means this could be nil.

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The other one is a non optional listing.

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The Raiders are getting more used to using it may not actually string a string and that has a value

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such as Hello.

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So I could actually take this out and go ahead in here and say Prince.

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Prince none optional string.

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So what do you think is going to happen when I run this application now before I can even run it.

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It tells me hey this variable needs to be initialized because it is not an option.

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It must have a value.

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So you either have to do it at a declaration time or you have to do it.

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Now this string is headed.

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So we'll use either of these two situations.

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We use optional values for when we don't know if anything is going to show up.

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For instance if I had a list of users something that we have done in the past and each of the users

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has certain number of photos but they don't know if they necessarily have photos or not.

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So I would have a photos or array of let's say you or I or not you images are strings.

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And then this would be actually an array and that is optional.

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I don't know if that thing actually is going to be mail or it is going to have IDs.

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So that's one thing.

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Well would they use non optional.

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Not optional.

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I will use it in situations where I know for a fact that that value exists and I know right off the

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beginning.

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So a situation like this where I'd have immediately said hey this value is going to be in this situation

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our i'm I've just started the OP that the moment I started I'm going to read the value from my user

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card username and then my username immediately is going to be our name of my youth.

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So in that situation we use none option.

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Finally we have something in of this caught on or off the street.

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Will talk about it in more detail in a minute but just look in the stand how it works is when you have

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optional listings.

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If I go in here and say preens option on this string is going to give me an error is going to say this

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is an optional string.

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So how do you want to convert it.

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Are you sure it exists like this.

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Or are you that find that either way a safe way to do it when you have an up to this train.

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And it is of that type whatever you want.

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Exclamation might.

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Then you can just place it in here because it will be treated right.

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This charade as if it was non optional.

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So once again this is not optional.

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Treated as if you know the value is always there.

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Up up this string is going to be treated as if it was not optional.

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It means its value is initialized immediately somehow the value for it is going to show up real soon.

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So with that in mind.

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And let me read you all these things a little bit.

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It's pretty nice.

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That's that.

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That's obviously not optional.

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This is the forced on dropped what happened.

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OK now let's see how are we going to go ahead about converting optionals into something that you know

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makes sense.

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So the first way is obviously force on writing for us on dropping which means we do something like print

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in the print I'm going to say optional this thing and I'm going to unwrap it.

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So whenever you have the sign of exclamation mark it's means on dropping either here are implicit on

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dropped or in here forced on rap of course.

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Maybe I can cut these and put them at the bottom because that's not what you're talking about.

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We're talking about this one the optional one.

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That's the force on rapping which is not safe not safe because you can't be sure if this value has something

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in it.

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As you can see in this situation right now I have the option of saying it is this thing but it is not

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going to be safe to force it.

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It doesn't have any value in it.

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It's not going to crash.

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It's going to give me a needle in this application.

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But in general if you have a value that value might very well you know be like the example I gave you

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were making it a logging in a user name.

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So we have to make sure that you know we don't force it.

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The other option is much better and much safer option is a conditional on wrapping.

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So how do we do conditional mapping.

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We have something called optional string.

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This is condition not conditional

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on mapping.

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So we have a value called optional history.

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I'm going to say if let's raise a string is optional a string then do something.

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So I'm essentially saying let's end oystering be that one.

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If it does exist do this.

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Print our value exists for instance.

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And then of course you can have an else which you decide about the other part of the other side if it

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doesn't exist.

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So if I run this application now obviously is going to crash in here because it's going to say you're

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forcing your value that is near.

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So I'm going to comment that out and then run the application.

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And then it says value doesn't exist simply because let's raise the string has never done anything in

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the optional string has always been known.

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Now let's do one other thing.

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What if you don't want to change this name.

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So you could actually do this you could say if left optional a string is optional a string then say

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value exist or let's just print the value.

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I'm going to say optional is saying the same thing in the else.

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Actually in the end I can't because you know I have to say it doesn't exist so again value doesn't exist.

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But what if somebody in the middle before we did this a statement I would have said optional testing

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is typing objective c.

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Now the value is going to be printed.

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So upshot is things you introduce them by a question mark at the end of them are optional values in

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general optional are integer optional flawed optional array whatever it is.

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If you want to force on them you just put an exclamation mark at the end of them.

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It is not safe.

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It is for when you're absolutely sure the value exists.

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Otherwise we use a conditional on wrapping to make sure that if flat the same name if you want if it

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equals to that and it doesn't become a value and there isn't that this thing will get a value is because

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actually string in here it's not optional.

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So I know I use the same name and it is becoming a little bit confusing.

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So I'm going to go with there is a string.

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I remember minor as a string doesn't have a question mark in front of it is not registering is in question.

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No it is a non optional.

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It's very similar to what we did here when we said that non optional is something I've said you feel

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that's that thing.

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It means that the value actually exists and then obviously based on that we can print it.

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And if it's not that thing if the else is happening we could decide what about for instance your luggin

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shouldn't happen because using name has been has not been provided.

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So there's finally another way of dropping an option.

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And that is using a type casting.

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So what I'm going to get myself a little bit of space in here and I'm going to say if I have an optional

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string I could do this I could say if option all this string as a string is not nil.

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And don't worry about the format of an IF statement.

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We will see that real soon in action in our next lesson which is about the control flow.

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So if that is not the case if it is not in there it's means we have a value.

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There is of course another easier way of doing this.

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Optional on dropping which is which is not as.

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As you know as funky as using an if let situation and that is this you could go in here and say if for

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optional string is not there then do whatever you want to do.

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For instance do this thing print that.

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I know this is not going to crash our application simply because it only happens if optional a string

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has a value in it.

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In this case it doesn't.

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So we know nothing is going to happen.

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So really quickly once again just to recover things that we discussed in this lesson.

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Actually I wouldn't mind if I rewrite everything.

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Real quick with an integer this time.

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So now I really have some some sort of understanding this should become a lot easier.

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So I'm going to say our my in and this might mean I'm going to give it a value right at the very beginning.

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And if you want I could actually say it is integer.

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So this is not optional and it means she is already so perfect.

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I'm going to have another one.

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Let's call it next.

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Integer is of that type integer and it's optional optional integer that needs to be on right before

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use.

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So we have to wrap this before we want to use it.

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And then finally there are on the integer which is integer and it has a little exclamation mark it is

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treated Azoff as if it was not optional.

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So let's see what do we do with all of these.

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If we go on to say print for instance to this thing are preens next integer next integer is an option

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or a value is going to crash this application.

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Now he's going to say you haven't really given me any value for it.

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I don't know if the value is nil.

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So you have to essentially give me a value if you try to force it say Hey I know it exists it's going

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to say well no it doesn't exist and it's going to crash application.

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So here's what you can do.

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You can say well if the next event is not net then do whatever you have to be doing.

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So that partially solves our problem a much better or more elegant solution for it is doing this saying

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if we let our next gain being next in us if that was let then do whatever you want to do then do what

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ever you want to do.

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All right.

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Otherwise it's still the net.

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So that's about that.

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I'm actually going to remove that because I want to write is for use we can have as a reference for

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future.

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So this will crash this one in here.

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Obviously it says what it is doing and you can do things such as this print on the top end and you don't

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need that exclamation mark.

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He's going to treat it as everything here reads

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as if it was not optional.

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All right you might actually keep this up as as like a cheat sheet for yourself.

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Non-optional us optional if it's Question My option is that of force on rap and it could potentially

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crash you have to use it and you are really really short and conditional on dropping some type of conditional

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on writing for when you are sure this thing actually.

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For it makes sure for you that this thing exists thing you say let something to be that thing.

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And finally when you want to use your implicitly arm dropped valueless now a more pressing question

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for you might be so where do I use either of these.

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Obviously use not option us for and you know what your value is.

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Almost immediately you use your optionals for when you don't know what is going to be there or is it

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going to be there.

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And you use your implicitly on dropped values for situations where there are value for that value but

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is going to be there or is going to be populated almost immediately.

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So you're reading a user your user most definitely has in name and has a unique ID and then you own

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your unique ID.

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You state as to be a and implicitly on up to one because it is not there now but it will be immediately.

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So that's about that.

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With all of that in mind Arved Let's move on to our next lesson.

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I have included a link to the optionals from the swift documentation.

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I would recommend you read through that as well because that really helps as well.