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Hello again.

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In this lecture we're using on collision, enter within our code to know when we bump, bump into something

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and we can make our code do something.

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In this case, we're just printing to the console that one object bumped into another object.

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So let's jump in and get started.

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First thing we need to do in this process is create ourselves some code that says we know when things

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bumped into other things and we're interested in saying, when did the player bump into anything else

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in the world?

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So I'm going to add a script to the player that says, Let me know when I bumped into something.

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And basically you could add all of this code into the one script you've got already.

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You could have a whole ton of different functionality in there, but that's bad practice because then

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you don't know what is going on.

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It makes this script really long.

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There's a lot to wade through, so it's better practice for each functionality that you need to make

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a new script.

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So let's right click in our assets area, create a C-sharp script.

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I'm going to call this collision hit enter and then open up collision from within here.

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We're not going to need start or updates, so I'm going to highlight all of those things from the comment

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up above.

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Start all the way down to the second last curly brace you see in here and delete that.

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So now we just have the open and the closed curly braces that say, what would you like to have in this

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class that's called collision.

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Okay.

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Well, tab in one little bit just there.

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And I'm going to use another in-built method that unity has similar to start and update.

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We've got something called on collision enter and we need the 2D version.

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Just like in the last lecture where we're talking about sometimes we use non 2D, sometimes we use 2D.

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When we're working in a 2D project with sprites, we need to use the 2D version of things.

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And so I clicked on that to complete it and we get a whole bunch of other stuff in here as part of the

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completion.

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So in general I delete the word private from my methods.

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Basically, private is a way of saying this can only be used in this class, it can't be used somewhere

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else.

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We can't update or change or modify or call this from somewhere else.

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That's what private does.

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But if we remove the private key word, it has exactly the same impact.

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So I remove it just to make things cleaner.

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But you can absolutely leave it there if you want that private keyword.

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And now what I also do is I fix up my curly bracket there so that I have it nice and neatly aligned.

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You can totally leave it on the line that it's on like that.

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That's totally fine because whitespace doesn't matter in C sharp in unity.

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So I could have it like that if I wanted to because the compiler is just going to ignore all that stuff.

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It doesn't care about.

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It doesn't care about whitespace.

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We can have our lines like that.

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We could do it like this if we wanted.

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We could have a whole space in between there.

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I think you get the picture.

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Riding it like this is totally valid.

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It'll work, but it looks a little bit ugly, I think, and a little bit messy.

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So I'm just going to undo all these things.

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And for me, what I like is to have my curly braces formatted like this.

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So I do that any time we get this kind of auto completion a lot, reformat it like that.

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And we also have some information that's being passed in collision to the other.

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All you need to know for now is that if we bump into something when we have a collision event, we can

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get information about the thing we bumped into.

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We can find its name, we can find details about it.

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We can change it if we want, says kind of cool.

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We don't actually need that for the little exercise we're doing now.

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So we could absolutely delete that.

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We don't need to have that information in there, but I'm going to leave that in, just undo and leave

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it in there because there's no harm in having it.

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But I just want you to know that this does a thing.

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We just don't need to use that thing just yet.

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So I have a little challenge for you here.

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This is something that we did in the very first section of the course.

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We printed something to the console.

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So the challenge I've got for you is to print something to the console using debug log print, a witty

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message to the console when we collide with something.

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So pause the video.

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Give that a go now.

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Okay.

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So we need to add this within our code block.

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So when we collide, we'll add something, we use debug log parentheses and then quotation marks.

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What am I going to say?

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I'm just going to say, ouch.

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Is that witty?

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I don't know.

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But I think it's kind of funny myself.

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Ouch semicolon save now back over into unity.

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So there's one last step in this process.

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Hopefully you figure this out when you're going through the challenge.

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But if not, what's the last step we need to do to print out to the console?

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Well, we need to click on our player and we need to add that script as a component so I can do it a

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couple of ways.

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One, I can click in here, grab collision, drag it in, or I can click on Add component and I can

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add collision.

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And you see our first one here is Collision, the script.

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Click on that and we have a collision script as a component on our vehicle.

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Now we'll click on console again and if we've set this up correctly and I click on play, turn towards

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my object, charge, blink, and I've bumped into it and it says Ouch.

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And you can see here in the console because we've got collapsed turned on, we've got a number all the

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way over in the right hand side that says how many times we've called that and printed that to the console.

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So if I back up and bounce back up and bounce back up and bounce, you can see that the number is going

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up to four.

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Now, what I could do is click on Collapse and then every time I bump into it, it will make a new line

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in the console.

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I've kind of pushed him all the way off the screen and see if I can push him back in again.

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Might need to cheat by looking at the scene window.

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Yep, yep.

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Okay.

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Push back into the world and you can see it'll add a new line.

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If I click on Collapse, it'll collapse it all so that we see how many is in there.

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Just a little trick there.

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In terms of printing the console, it's really handy to use debug statements printing to the console

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when you're doing things, particularly with collisions.

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So, you know, collisions actually working and you're not sitting there scratching your head because

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it's saying, Yep, I bumped into a thing which is really handy to do.

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So that's the fundamentals of using collision to make things happen.

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In our game.

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I have a rigid body on at least one of these objects.

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In this case, we have a rigid body on both.

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But you need to read your body on at least one, and we need to have our colliders on both of these

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objects.

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Both objects need to have collider and now we can say when we bump into something, we can make our

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code do particular things.

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For the moment we're just printing out to the console, but we can do more interesting things in the

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future when we bump into things within our world.

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So there we go.

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That's using on collision.

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Enter within our game.

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I'll see you in the next lecture.