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Hey buddy what's going on.

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This is Caleb with Debb slopes dot com and in this video we're going to talk about optionals and optionals

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are an amazing part of the swift programming language.

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And I want you to think about an optional sort of like a rapper or like a box.

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OK.

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Now it can hold something right like a box can have something inside of it.

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A wrapper can have some type of maybe food or even like a drink if you think of like a drink container

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it can hold something or it can be empty.

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OK.

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That's like that's what an optional is sort of like it can have a value or it cannot have a value.

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Now imagine you got a package delivered from Amazon.

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When you pick it up off your front porch there can be something inside but it's possible that at the

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fulfillment center there was a mishap and maybe your box is empty which of course that would be really

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disappointing and kind of a lame thing but that is possible.

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The idea behind optionals is that we can safely use the box without having to worry what's inside.

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OK.

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That is the cool thing about optionals So let's go ahead let's pull open a brand new X code playground.

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So open up X code and in this little welcome to X code menu click get started with a playground and

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we're going to do a blank playground and I'm going to call this shoes optional.

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Just you know instead of clothing optional just say shoes optional little more appropriate anyway create

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it and let's pull it open.

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Full size.

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There we go.

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By the way if you're wondering how I'm doing that I can make it take up the left side of the screen

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the right side of the screen.

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Anything like that.

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Pretty neat.

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It's a little app called shoot.

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What is it called a magnet.

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Right.

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It's called Magnet.

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There's another one called flexi glass.

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I just happen to like magnet a little bit better.

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Anyway let's get started.

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So I'm going to go ahead and get rid of that variable there and I'm going to get rid of that little

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commented line there.

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And I want to show you how optionals can work and I'm going to use some images to represent them.

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So I'm going to create an optional image and I'm going to create a non optional image so I'm going to

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show you how you declare a variable as optional.

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So go ahead and type let optional image and we're going to make it of type UI image but I'm going to

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declare it is optional by putting a question mark at the end of the type declaration.

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Now of course as it currently exists it is optional.

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It can have a value.

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It can not have a value meaning it's able to be nil or it's able to be or to have a value.

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And I'm going to go ahead and give it a value just for the explanation purposes of this.

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And so I'm going to insert an image literal from the editor menu and I'm going to drop in that image

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right there.

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OK now I'm going to add a viewer so we can see the image.

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All righty and that's great.

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So there it is.

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This is an image representation of what an optional is like it's a box but it can be empty meaning it

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can have a nil value.

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Now let's go ahead and create let non optional image and we're going to make that of Type II image K

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and we're not going to put a question mark meaning it has a literal value.

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We're going to go ahead and insert an image literal and I'm going to use this image to represent that.

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And when I pull open this viewer you can see what I mean.

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This non-optional image.

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Well it's an image but it represents an optional with a value of five.

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So this optional can have a value of 5 or can have a value of nil.

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That's pretty cool.

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Now I'm going to show you ways that you can actually use optionals and then some things we need to be

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careful about as well as at the end I'm going to show you kind of a real life example of using optionals.

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So we're going to go ahead and talk about forced unwrapping.

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So go ahead and type a variable here.

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Var optional number k.

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And we're going to make it of type int.

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Although we're going to make it optional.

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OK so this could be for something maybe that we don't know if it's going to have a value or not.

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Although I'm going to set it to have a value of 5 K so it's optional but it has a value of 5 and I'll

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show you how this works in just a moment.

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Next we're going to go ahead and just create another variable of type and and make it equal to 5 as

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well.

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Now you'll notice the second one is not optional.

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So what I can do here is I can say if optional number is not equal to nil OK meaning if it is not nil.

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We're going to print and we're going to put something in the print statement that says optional number

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has a value of and will use string interpolation here to pull out the value of optional number and we

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will go like that and pass it.

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The value for optional number because we have given it a value right.

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We say optional number has a value of optional number.

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Now you'll notice when it prints out it says optional number has a value of optional 5.

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Now you're wondering well why is that.

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This is a way that swift keeps a safe when we're programming.

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Since it is optional it's passing in the value for 5 but it's keeping track that it's an optional value

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and that it could be nil.

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Now watch what happens if I change it to nil meaning I give it a nil value of value of nothing.

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You'll notice nothing happens because we're checking to see if optional number is nil.

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So let's turn it back to 5.

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But I said we're talking about force unwrapping.

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Now this optional number variable has an optional value of 5.

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But in order to actually access the real value we need to use an exclamation mark to force unwrap it.

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It's like we're opening the box and taking the value 5 out.

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We're actually getting it from the box.

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So that's Force unwrapping.

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But watch what happens if I change this.

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Let's just say I take away this conditional check.

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This is to show you the danger of using an optional.

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Watch what happens if I change it to nil fatal error unexpectedly found nil while unwrapping an optional

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value.

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That's a problem so this is where we need to be careful with force on wrapping.

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You need to basically set up conditional code to check to make sure that it's not nil.

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And you might be wondering well why would I ever have an optional value.

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Think about if you're pulling data from a server and you're not sure that a certain value will come

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back of a certain type every single time.

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It would be better to set it as nil or sorry I said as an optional in case the value returns nil so

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if that were to happen you could say if it's not nil.

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Do something else.

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And then here you could basically set it up so that it would handle any errors.

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Ok that is just one way you could use optionals.

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Kate gives us the option right.

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That's the optional thing.

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It gives us the option of basically using a value or a non-value.

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So here we go.

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Let's go ahead and move on.

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That's for Sun wrapping.

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That's how you take an optional value and you force unwrap it into something that is an actual value.

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Pretty cool.

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Now I'm going to go ahead and just close these viewers here they're giving us some trouble.

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And let's move on.

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So next up we're going to go ahead and check out something called optional binding.

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OK.

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Now what we're going to do with optional binding is we're going to basically take an optional value

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and we're going to bind it to a non optional constant.

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But the cool thing is that we will use an IF statement to handle what happens if the optional number

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comes in as nil.

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So check it out.

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If we go ahead and type if let And then we can say constant number K-Stew we just created a constant

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called constant number.

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We're going to set it to be equal to optional number.

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All right so now we have a constant that has a definite value of optional number.

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But what happens if constant number is not.

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What if we can't set the value of constant number what if optional number is actually nil.

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That would cause a problem.

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So what we're going to do is we're going to print let's print out what we see here.

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Constant number has a value of.

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And we'll print out constant number.

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OK.

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Now when this runs you'll see that it actually does print.

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We are creating a constant called constant number and when it runs lets run it and you'll see it'll

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print out constant number has a value of constant number but it's not doing anything.

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That's because our value is nil.

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And that's where our else block comes in when we're doing optional binding we're basically binding an

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optional value to a constant.

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But we're using an if else so that we can handle both cases value or no value.

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So if we can create the constant and set it to be optional number it'll print that out.

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Otherwise we will print what is it.

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Let's see optional number is nil because that's what it means it must be nil if that's if that's what

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is happening and as you can see optional number is nil.

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And so that is where we could handle errors just like I said above.

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But the cool thing is that we can use constant number as a way of creating a non optional value do you

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notice how we don't have to force on wrap this.

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Watch what happens when I set it to be a value of five optional number and Konst that number has a value

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of five that basically allows us to create a non-optional constant from an optional.

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Pretty cool.

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So that is optional binding you know what let me go ahead and put some notes here so we don't forget

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this was force unwrapping force unwrapping.

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Whoops.

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Anyway moving on.

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So let's go ahead and I want to show you another example.

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I'm going to create a function here called into printer and it's basically just going to print out an

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integer value.

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Now I can also use optional binding within the guard let check it out.

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Guard let constant number just like above.

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And we're going to set it to be equal to optional number.

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If we can't do that right.

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Meaning if it's nil we're just going to go ahead and say return just like that.

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Now assuming that we do get a value we're going to go ahead and print constant number has a value value

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of

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what is it optional number a constant number.

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We'll just say constant number because it will be the same as optional number.

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Cool cool.

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So we've used the guard let to say if optional number has a value.

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Set it to be equal to or set constant number to be equal to optional number.

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Otherwise return and get out of the function.

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So let's go ahead and let's call in printer.

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Whoops there we go.

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And when it runs you'll see that it prints it out right there a third time.

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But watch what happens if I set optional number to be equal to nil or have no value.

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It doesn't print.

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The only one that prints is our first one where we forced unwrap the value or sorry where it where we

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tried to bind it.

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But if we couldn't bind it then we would print out optional numbers nil.

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So change it back to have a value 5 and we're going to move on now.

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We're going to talk about what are called implicitly implicitly unwrapped optionals.

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OK.

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So implicitly unwrapped optional is basically where we are going to force unwrap a value from the very

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beginning.

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So to do that we can just say I'm going to assume that a value is coming in as maybe 5 so let assumed

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value of type int equals five.

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But if we're going to make this implicitly unwrapped we're going to go ahead and put an exclamation

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mark.

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That means we are force on wrapping that value.

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So what we're going to do next is we can just say let implicit value of type and equals assumed value.

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OK.

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So we are able to create a value you can see over here that it does create a value of 5 but watch what

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happens if I make it.

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Nil we get an error unexpectedly found nil while unwrapping an optional value.

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So unless you are one million percent sure do not implicitly unwrap optionals this is kind of a last

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ditch thing.

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It's kind of if you have to if you're not 100 percent sure that there's a value.

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Do not force on rap or implicitly unwrap values like that.

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OK it's not good practice.

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OK so next up there's kind of a really cool thing I want to show you with optionals called nyl coalescing

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and something called using the ternary operator.

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So let's go ahead and call and nyl coalescing and using turn very operator.

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So we're going to create an optional integer.

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OK so go ahead and type let optional end of type int equals nil and you'll see if we do this it's going

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to not let us it'll say we can't use nil on something of type int because nil is not an integer value.

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But if we set it to be an optional that means that we basically put that in a box and we say OK the

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box can have a nil value or it can have a numerical value so that's cool and all but what if we want

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to create a variable but we're not sure if optional end is going to have a value or not.

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Maybe we're pulling data from a server so we can say let results equals and watch what we can do.

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We can say it equals the optional and but what if you're not sure.

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Now if it comes back with value like if we gave it the value five that's great and now optional is equal

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to five therefore result is equal to five.

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But if it comes back nil we might not want to set it to be nil right.

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That would cause a crash in our application.

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So what we can do is we can use the turn every operator by doing two question marks.

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Then after that we can type is zero.

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And what this is basically saying and you'll see it as it prints out is if we don't get a value set

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it to zero.

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Otherwise set it to be optional.

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And so this is kind of like like else.

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Think.

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Think of it like this optional it has a value.

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Let results equal optional.

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And if there's a value otherwise set it to be zero.

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Meaning if Neal comes through it's going to set it to zero.

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Just like you can see now if I said it to five you'll see that the optional will print out as 5 because

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it adds value.

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Really really cool.

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So let's go and set it to nil just because it's pretty cool that it's using the ternary operator there

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and last but not least we're going to go ahead and use a real world example with Comic-Con.

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I'm going to Comic-Con next month and I'm really excited.

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So I was thinking about it and thought it was a perfect example for what we're going to do.

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So first of all we need to create a class for Comic-Con attendee and we need to create a class for their

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admission badge.

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So go ahead and type class comic con and the K and we need a variable we need an admission badge like

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so of type admission badge which That's a class will create in a second but we're going to make it optional

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because everybody who goes to Comic-Con they might not have a badge from the very beginning they might

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want to buy tickets when they get there.

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So we need to create a quick initialiser and we're just going to say badge of type admission badge and

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that of course is optional because they may or may not have a badge and we'll just say self admission

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badge is equal to badge just like that.

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OK so now we're going to create the admission badge class so that our attendees can actually attend.

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That would be helpful.

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So type class admission badge and let's go ahead and just say for Comic-Con we're just going to give

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a variable number of days.

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That's usually how Comic-Con tickets go.

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And every bag is going to have an explicit value so we don't need to make it optional and we just need

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to initialize it.

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So go ahead and type number of days of type int and we'll set self number of days to be equal to number

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of days.

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Very cool.

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So what we're going to do is we're going to create an admission badge.

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We're going to create a Comic-Con attendee and we're going to give them that admission badge so go ahead

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and type let admission badge equals admission badge and we're going to pass in a number of days.

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Let's just give them a three day pass and now we're going to create a Comic-Con attendee.

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So let attendee equals Comic-Con attendee and need to give them a badge so go ahead and pass in the

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admission badge.

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And just like that we have an admission badge and we have a Comic-Con attendee which is really cool.

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But if I was building an app where I wanted to show how many days left you have on your Comic-Con badge

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I might type something like this if let days a tenable meaning I have X amount of days left.

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We can check that by going in to attend the admission badge end did you notice admission badge is optional.

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You can see that right there and watch what happens when I type that number of days.

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That's because I might not have an admission badge.

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OK.

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So it's putting an optional there so that it is safely unwrapping and safely using the value in my admission

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badge.

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So if there's amendable is equal to number of days which in this case is three we're going to go ahead

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and print whips.

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We're going to print this attendee can enter Comic-Con for.

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We're going to print the number of days here days a tenable days.

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Else we're going to print something else.

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Now we didn't think what would we print if days a tenable is not equal or if days a tenable number of

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days comes back as.

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We need to say this person has not yet purchased a ticket.

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Please refer them to the ticketing window and watch what happens when we print this out.

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OK.

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So it says this attendee can enter Comic-Con for three days but watch what happens if I remove the admission

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badge remember for a Comic-Con attendee admission badge is optional so I can pass in Knill.

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What if I did not have an admission badge.

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If it comes in is nil.

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Watch what happens.

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This person has not yet purchased a ticket.

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Please refer them to the ticketing window because I was using optional binding and that basically created

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a constant here called days attend table and I set it to be equal to the number of days from the admission

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badge.

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But if the admission badge is nil then I get an optional value of nil and it prints out here.

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This person has not yet purchased the ticket.

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This is called Let me put it up here at the very top.

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This is called optional chaining and it allows us to change values of optionals together so that we

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can get a value or handle errors when it returns nil optionals are incredibly helpful and I really hope

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that you can see that these are just some super helpful small examples of using optionals And of course

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if you're confused or if you want to know more.

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I would highly recommend digging into the Apple documentation.

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There are tons of examples there.

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So amazing work with this video.

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And let's head over to the next one.