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‫Hey.

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‫Welcome back.

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‫Now we've set ourselves up with a callback function bound to the delegate on take any damage.

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‫And the last step is to actually generate that damage event.

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‫And we want to do this when our projectile hits something.

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‫Once we broadcast for this delegate, we can apply damage to the thing that we hit.

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‫And we're going to broadcast this event using applied damage, which belongs to the gameplay statics

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‫class.

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‫So let's take a look at the applied damage function.

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‫Now here's the documentation for applied damage it says hurts the specified actor with generic damage.

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‫So this is a generic function for applying damage.

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‫And what we do in response to broadcasting for this delegate is up to us.

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‫Now here we see we need to include gameplay statics and in the syntax we see several input parameters.

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‫Now we actually get some description of the parameters.

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‫If we keep scrolling down, we see that damaged actor is well, the actor that will be damaged base

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‫damage is the base damage to apply really descriptive documentation here.

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‫Thanks.

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‫Epic event instigator is the controller that was responsible for causing this damage.

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‫And it says, for instance, the player who shot the weapon.

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‫When it says player, it's referring to that controller.

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‫Then we have the damage causer, which is the actor that actually caused the damage.

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‫It says the grenade that exploded.

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‫In our case, it'll be the projectile that exploded.

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‫And finally, we have damage type class, which is a class that describes the damage that was done.

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‫Now back up in the syntax section, we can see the types of these inputs and we see that damage type

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‫class is a subclass of and we've seen before that TW subclass of will satisfy an input parameter of

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‫type U class.

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‫Well when we call apply damage, we can pass in a U class representing the damage type we'd like to

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‫use.

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‫So we'll talk about how we're going to satisfy this input parameter in just a moment.

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‫So the hue gameplay statics function, applied damage is going to take a few input parameters.

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‫So let's strategize on how we're going to pass in the appropriate values when we call this function,

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‫we saw that first we need the damaged actor.

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‫Well, let's go back into projectile CP where we'd like to call apply damage.

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‫We'd like to do it here in on hit and we no longer need these logs.

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‫So I'm simply going to remove them and notice that our on hit callback gets some inputs passed in once

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‫it gets called.

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‫When the on component hit delegate is broadcast, we'll see that we have other actor.

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‫So we have access to the actor that got hit by the projectile and this is the actor we would like to

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‫damage.

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‫So that takes care of the first input parameter.

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‫It's going to be that other actor.

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‫Next, we need the damage amount, which means our projectile should have a damage variable so that

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‫we know how much damage to apply.

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‫So why don't we go into projectile FX and add a damage variable and this can be a float.

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‫So we can simply call this damage and we can initialize it to a value, let's say something like 50

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‫F and since this is something we'd probably want to experiment with, we can give this a U property

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‫to expose it and make it edit anywhere.

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‫So now we have a damage amount to pass in when we call take damage.

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‫Now the next parameter is the instigator and we saw that this is of type A controller.

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‫So how are we going to get the controller?

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‫Well, we've seen that we can get the owner of a particular component with the get owner function.

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‫And this returns the actor that owns a particular component, these projectiles are being spawned dynamically.

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‫So we need to make sure if we're going to be calling get owner that the owner is set now we're spawning

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‫these from base pawn.

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‫So if we go into base pawn.

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‫CP Here's the line where we're spawning the actor, but Spawn Actor also returns a pointer to the actor

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‫that was spawned so we could store this in a local variable.

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‫For example, we could say auto projectile and assign the value returned from spawn actor.

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‫Now if you're not familiar with auto, it allows the compiler to figure out the type to assign to this

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‫new variable.

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‫If you hover over it, you'll see that it has the type A projectile pointer because that is what we're

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‫signing from the spawn actor function.

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‫So this is the same as if we had put a projectile pointer right here and now we can access that newly

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‫spawned projectile.

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‫And the reason we want to do that is we'd like to set its owner.

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‫We would like to make sure that its owner is set to the pawn that spawned it.

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‫So we can say projectile.

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‫And there's a function for this called set owner.

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‫Set owner takes an actor and we're going to pass in this so that whenever one of our pawns spawns a

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‫projectile, it will set that projectiles owner.

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‫So that way, if we ever call get owner further down the line, we'll get the instance of the class

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‫that owns that projectile.

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‫So back here in projectile DHCP, we have our get owner function call and we can store this in a local

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‫variable.

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‫I'm going to go ahead and use auto again and call this my owner and set it to the result returned by

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‫get owner.

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‫So now we have a local actor pointer that stores the value of the owner.

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‫Now we can access the instigator controller from this actor.

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‫Now, before we do so, it's a good idea to check to make sure my owner isn't null.

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‫So I'm going to say if my owner is null equals equals null pointer, then I'm simply going to return.

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‫Now, if you're if body has a single statement like this, you can place it on the same line without

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‫the curly braces in case you didn't know.

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‫And null pointer is a keyword in C++ that allows you to check to see if a pointer is a null pointer.

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‫So if my owner is null, then we will return out of the function early and not do anything else.

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‫Now, as I was saying, we can get the instigator controller from my owner and that's what the use of

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‫the function called get instigator controller.

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‫And if we hover over this, we'll see that it returns an A controller pointer.

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‫I'm simply going to use auto and store this in a local variable that I'll call my owner instigator.

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‫So now we know what to pass in as the instigator.

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‫The next input is the damage causer and this is the actor doing the damage for the projectile.

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‫This is going to simply be this.

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‫And that leaves the last input parameter, which is a damage type.

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‫And we saw that it's a subclass of which means we need the proper use class to pass.

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‫N Now here's the unreal engine documentation for you damage type.

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‫It says a damage type is intended to define and describe a particular form of damage and to provide

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‫an avenue for customizing responses to damage from various sources.

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‫Now, we're not going to customize our damage.

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‫We just need to satisfy the input parameter, which means we need a U class value that represents this

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‫you damage type class.

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‫Now in C++, if we want to get the YOU class of any particular class such as you damage type, we can

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‫call a function called static class.

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‫This is inherited from the you object class.

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‫Now of course we're using you damage type here so we'll need that header.

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‫So from the documentation I will copy the include line and I'll paste it up here at the top of projectile

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‫CP And now you'll see that this static class function returns a U class pointer and that new class will

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‫represent the new damage type C++ class.

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‫Now, since we're not creating a blueprint based on you damage type and setting some extra data, we

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‫don't really need a subclass of variable.

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‫So in this case we can use static class and this will return a U class that represents this type.

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‫And we can store this in a variable if we like, and I'll call this damage type class.

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‫And this is what we can pass in as the final parameter to apply damage.

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‫So we now have all of the information we need to pass into the apply damage function.

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‫But before we do so, I'd like to place a couple of checks to make sure it's appropriate that we call

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‫this function.

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‫So I'll make an if statement here.

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‫First, I want to make sure that other actor is not null.

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‫So I'm going to place other actor here.

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‫I'm going to place an and here so I can check to make sure other actor is not equal to this actor.

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‫We don't want to cause damage to ourselves if we are the projectile now I'm going to place another end

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‫and make sure that other actor is not equal to my owner.

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‫It wouldn't be good if the projectile is causing damage to its owner.

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‫And now if we get inside this if statement, then we know that it's appropriate to call apply damage

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‫so we can do so.

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‫And that's going to be your challenge.

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‫So in our new if statement in the on hit function call the you game play statics apply damage function.

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‫This means you'll need to include the correct header for gameplay statics and you know which input parameters

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‫to pass in.

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‫So pause the video and add the function call to apply damage in the on hit function now.

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‫Okay.

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‫So I'm here in projectile CP and I'm going to include the header file for gameplay statics and we can

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‫see from the Applied Damage Documentation page that the include is kismet slash gameplay statics.

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‫So I'm going to paste that in there and now I'm ready to call apply damage.

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‫So I'm going to call you gameplay statics apply damage.

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‫Now as soon as I type that opening parentheses, I get the pop up reminding me of the input parameters

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‫I need.

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‫And the first one is the damaged actor and that's going to be other actor.

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‫So we're going to type other actor next.

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‫We need the damage amount and we added this damage float in projectile FX, which we set to 50.

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‫So I'm going to pass damage end next.

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‫We need the instigator and we have my owner instigator.

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‫So I'm going to pass in my owner instigator.

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‫Next is the damage causer.

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‫And of course, the projectile itself is the damage causer.

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‫So we're going to pass in this.

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‫And finally we need the subclass of for you damage type which we know a U class pointer will satisfy

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‫that and that's why we have our damage type class.

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‫So let's pass in damage type class.

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‫And with that we're now calling apply damage.

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‫So when we call this, we will generate the damage event and the on take any damage delegate will broadcast

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‫in response to this, which means in our health component damage taken will be called.

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‫So we just need to do something here in damage taken.

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‫Well, it would make sense to take this damage and subtract that amount from the health.

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‫Before we do that, though, I'd like to make sure that damage is not less than or equal to zero.

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‫F It makes sense to make these checks before documenting damage, just to make sure that we don't apply

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‫a value that doesn't make any sense, like zero or a negative value.

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‫So if that's the case, we'll simply return.

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‫And of course, if you'd like to be slick and do what I did in projectile at CP, we can place the return

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‫right there.

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‫Now, if we make it past this line, damage is a positive value so we can take health and use minus

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‫equals damage.

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‫And just to make sure that this is working, why don't we place a euy log here?

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‫So Yui log log, temp warning text and we can simply print the value of health with percent F and health

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‫and with that we can compile.

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‫Now with a successful compile, we'll hop back into the editor and with our output log open, let's

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‫hit play.

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‫Now let's see if we can get hit by a projectile.

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‫And there we go.

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‫Our health is now down to 50 and if we get hit again, we got quite a few hit events because we were

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‫hitting up against the projectile many times very quickly.

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‫But we see that our health is documenting properly.

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‫So we do need to make sure we implement the correct behavior upon death when health reaches zero.

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‫But we also need to make sure that we don't get this hit event spammed multiple times.

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‫Now we know that the projectile should be destroyed upon hitting something, so the best way to prevent

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‫spamming the hit event is to destroy the projectile.

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‫So that's the last thing we'll do in this video.

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‫So back in projectile just after applied damage, what we can do is have the projectile destroy itself

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‫and that couldn't be easier.

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‫We simply call the destroy function.

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‫So with one more compile back here in the editor, we can go ahead and get hit by a projectile and look

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‫at that.

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‫The projectile is gone.

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‫So it does its damage and then it disappears.

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‫And of course we can test out hitting the towers as well by blasting them with projectiles and making

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‫sure that those hit events are triggering.

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‫And as you can see, I can spam this with a whole bunch of projectiles and we'll see that the health

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‫value for this poor tower here is getting very, very negative.

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‫So in summary, we called the apply damage function and this resulted in a broadcast for the on take

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‫any damage delegate.

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‫We documented the health in the health component and we destroyed the projectile.

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‫So we've now taken care of damage.

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‫We have not yet taken care of death.

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‫So that will be one of the next things we'll cover in a future video.

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‫I'll see you soon.