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In this video, we're going to fix a situation where the player could drive straight over to the customer

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and deliver the package, but they didn't actually ever pick up the package.

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So we want to make sure you can only deliver the package if you actually have the package.

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How do we do that?

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Well, we're going to do that using a bull.

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What is a bull?

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I hear you ask.

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Well, bulls are types of variables that can store one of two values, either true or false, and they're

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often used with if statements to decide whether something happens or not.

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So if something's true, do the thing.

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If it's false, don't do the thing.

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So bulls are very handy from that point of view.

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And in our code we're going to jump back over into our delivery script and write up the top up above

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our own collision.

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Enter right up here.

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We're going to create ourselves a variable which be of type bull and we'll call this has package.

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You want to make sure that you name your bulls in a way that it's clear that it's either true or false

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has packaged its true or has package is false.

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If you just name this for example package, what does that mean?

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Does it make sense?

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Does it mean it's a big package or small package or red package or blue package?

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But if we say has package, then that's do I have it or not?

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And we do semicolon here now.

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We didn't actually assign a value to it so we could assign it false to say we're pretty sure when the

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player starts the game it's going to be false or we could have signed it as true.

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When you start, you've got the package.

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It's true.

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But just a little experiment here.

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If we don't assign it anything, what will it be?

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How do we know?

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Well, we could go and Google the answer what the bulls default for in unity or we can do ourselves.

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Just a little quick experiment.

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We'll start and start or delete this again in a moment and start and we'll debug dot log and in our

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parentheses what is type has package and then semicolon.

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So what that would do when we first start our game, it'll just print out whether it has packages,

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true or false.

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So we'll save that back over into unity.

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We'll just do this as a little thought experiment.

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I also want to get you in the habit of doing printing things to the console so you know what's going

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on.

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You're constantly testing and looking and not getting sideswiped by these things, so it starts off

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as false.

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So we know for sure this starts off as false.

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That means that we won't be able to deliver the package until we actually go and get the package.

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So how do we get the package?

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Well, in our on trigger enter, we've got the if the other tag is package, then we want to pick it

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up.

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What would we do in this instance?

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After we pick it up, we want to change our ball to be something we want to change it to be has package

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equals what equals true.

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So the logic here is if we bump into something that is the package now that has package ball or that

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has package variable, we'll be true.

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Excellent.

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When we bump into the customer, we need a way of saying okay, the other tag has to be the customer

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and you actually need to have the package, my friend, or else I'm not going to accept delivery.

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The way we can do that is in our if statement.

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We can have multiple things.

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We're checking to see whether they're true or not.

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So it can be saying, is it the customer?

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And then we can use the double ampersand.

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That's what that little symbol is called, ampersand or it's called the end sign.

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So you do two and back to back that's the and operator and then we're going to type in simply has package

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we don't need to say has package equals true you could do that but you don't need to because when you

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just add in the variable in here, it's going to say, okay, it's a ball.

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If it's true, do the thing.

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If it's false, don't do the thing.

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So let's save that and see if that actually works.

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We'll do, first of all, by driving over our customer and see what message we get.

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Make sure we don't accidentally pick up the package.

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Drive, drive, drive, drive.

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What happens here?

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Nothing.

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Nothing gets printed.

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The customer is like, well, unless we bump into the house and it says, ouch.

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Customer is like, No, man, I don't know what you're talking about.

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We go over, we get the package now we've got the package picked up, drive back over to the customer

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and yes, package delivered.

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Excellent.

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However, what's going on here?

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Oh, I can keep delivering the package.

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I'll deliver it another time and get, you know, suite, bonus and commission and another commission.

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Okay.

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So we need to do something so that we can't keep doing that.

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We can't exploit that because, you know, your players absolutely exploit that.

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So little challenge for you here.

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I don't have a slide, but the challenge is add some logic to make sure that we can't deliver the package

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over and over.

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So what do you think we would do?

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Pause the video and have a go at that?

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So in logic we need to say once we've delivered the package, then we don't have the package anymore.

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So has package is going to equal false and let's just check that that works.

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Before we celebrate too much, click on play.

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We'll go through this standard process.

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We'll make sure that we can't deliver it until we have it.

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No, we can't.

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We'll grab it and then we'll bump into a tree, then we'll deliver it.

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Yes.

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Package delivered.

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And then is it going up?

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No, the number doesn't go up.

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But if we go back over, we grab the package again and then drive back over.

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It does go up exactly as we want it to do.

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So there we go.

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We've used a ball in conjunction with our if statement to make sure that we can only deliver the package

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if we have the package.

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Okay, I'll see you in the next lecture.