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‫Hello and welcome.

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‫In this lecture we are going to be implementing our own class member functions, move platform and rotate

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‫platform.

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‫We're going to see how we can set them up so that they can take in arguments.

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‫And it's going to help us tidy up our code a little bit.

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‫Let's dive in and see how this works.

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‫So up until now, we've been using C++ functions that have already been created for us.

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‫We've been using TIC V using big in play in terms of writing their functionality.

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‫And we've also been using functions that other people have written for us.

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‫We've been calling them such as get active location and get name.

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‫Now how can we go about creating new own functions to help organize our code and keep these functions

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‫small and everything much more legible?

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‫Well, we've got the basic building blocks already in place by getting towards the end of the section.

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‫We understand a lot more about C++ syntax.

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‫So what I want to do is essentially create a new function on the moving platform that allows us to have

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‫just intake, say call move platform.

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‫Why do I want to do that?

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‫Well, because being able to make a function call like this called MOVE Platform, it really speaks

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‫to what we're trying to do at the moment.

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‫We've got a lot of stuff going on in tech and I'm not entirely clear why we are doing all this stuff

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‫if I just come and take a glance at it, if I went into tech and saw a function that says Move platform,

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‫well then suddenly I have the context for what all this stuff should be doing, and I don't need a single

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‫comment to tell me what's going on.

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‫And this is going to be particularly useful when we add into the mix the possibility of rotating the

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‫platform as well.

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‫So how do we define declare functions?

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‫Well, the declaration aspect is done over in the header file.

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‫That's where we basically say a heads up to C++, we're going to have a function that's going to look

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‫kind of like this.

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‫And then over in the C++ is where we actually define the function.

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‫We give it the body, we tell it exactly to C++.

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‫This is how the function works.

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‫And let's have a look at how we can do this.

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‫We've got a few examples of functions and they got big in play.

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‫We've got tick and it's a good point in time for us to look at the different sections that we've got

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‫in our header file.

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‫We've got public and protected being mentioned here and public being mentioned again.

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‫Now what does this mean?

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‫These key words with the colon at the end basically define a section of accessibility.

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‫These functions, where can they be accessed from?

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‫We've seen over in the get safe normal.

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‫This is a function that we're calling on an F vector, but we're calling on it from another class,

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‫not from within an F vector.

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‫So this means that the accessibility of this function needs to be public.

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‫Now we'll leave aside protected just for the minute because it gets a little bit more complicated there.

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‫But there is another type of key word that we can use, which is private.

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‫So I'm going to add after tick, I'm going to add the private key word.

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‫Notice that I don't indent these sections and we're going to put a code on at the end.

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‫And that means that everything that comes afterwards until the next section, the next key word that

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‫I put in here is going to be private.

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‫So that means we've taken all of these variables and said, hey, no other class is allowed to touch

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‫these.

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‫And that's usually the best practice.

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‫We haven't done it up to this point because I didn't want to get things a little bit too confusing for

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‫you.

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‫But variables in classes should generally be their own business.

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‫It's one of the core tenants of object oriented programming that we leave classes to manage their own

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‫variables, and we only access them using functions that the class denotes as being public.

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‫So what we're going to do here is we're going to add some more private functions in here because we

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‫don't want something like Move Platform to be called from outside of the class.

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‫We want it to be managed by our own tick function.

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‫So how do we define a private function?

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‫Well, we put it in a private section.

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‫So we've got our private key word up here.

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‫I'm going to put it after our variables, however, and we start off with the return type.

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‫And if our function doesn't return anything, we just type void to indicate that there's no return coming

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‫out of this function.

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‫Then we give it a function name.

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‫So we had move platform was what we wanted and then we give it some parentheses to indicate that this

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‫is a function open and close parentheses and then a semicolon to finish off the line and say, okay,

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‫that's it.

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‫That is the function that I want to declare here in the header file and all that does.

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‫It says this is the shape of the function, this is the return, this is what parameters it takes and

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‫the name and which class it belongs to.

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‫Now, to actually give it an implementation, we have to define it over in the C++ file.

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‫So let's go over there.

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‫And at the end of the file, just outside of any curly braces, this is where we do it.

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‫We start again with the return type.

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‫So that's going to be void then because we're inside a C++ file, we're not inside the curly braces

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‫of a class.

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‫We have to use the scope resolution operator to say that we're we're trying to define a function from

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‫within the moving platform class.

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‫So we type the name of the class, which is a moving platform, remembering that a prefix is there to

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‫say that it's an actor.

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‫Then we use colon, colon, the scope resolution operator, and then we use the name of the function

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‫we're defining, which is MOVE platform, and then we use the same set of parameters as we did in the

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‫header file.

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‫In this case, we had an empty set of parameters, so we just have the parentheses.

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‫And then instead of putting a semicolon at the end of this line on a new line, we put an opening curly

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‫brace and a corresponding closing curly brace.

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‫And between these curly braces where we put the code for our function, fantastic.

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‫So what I want to do now is try and say, well, all of this functionality we've got here, and in fact,

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‫I'm going to delete the comments because we no longer need them.

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‫They were the pseudocode we used to implement this, but now it's kind of served its purpose.

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‫We understand what the lines of code are doing.

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‫I'm going to take everything but the MOVE platform function out of TTIC and copy it and paste it into

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‫our MOVE platform function instead.

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‫So this should work pretty much the same because when we go into tick, we then call move platform and

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‫it just runs the same piece of code.

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‫Except now we've bundled it into a function and it makes it easier for us to read and potentially reuse

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‫in the future.

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‫But if you do do this, you will notice there is a problem.

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‫We are accessing Delta time and that is a parameter we no longer have access to because it was a parameter

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‫passed into tick.

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‫So if we want to get hold of that, we do need to have a parameter in our function.

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‫So when we define parameters, we have to do it in two places.

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‫Just like when we define the function, we go back over to the header file and between the parentheses

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‫of our MOVE platform function.

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‫This is where we say what parameters we want and it's exactly like defining a variable.

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‫You need to give it a type and you need to give it a name.

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‫So we're going to say it's going to be a type float and we can just call it Delta Time.

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‫It doesn't have to be the same name.

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‫We could call it D.T., we could call it time.

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‫But the it's easier to give it the same name because then it's obvious to anyone reading it what should

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‫be passed in here.

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‫Then over in the C++ file, we need to match the list of parameters.

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‫So again, you can just do this by copying and pasting or by typing it out.

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‫If you type it out, make sure you don't make any typos because the compiler will complain.

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‫So we're going to have a float called Delta Time passed in as a parameter or defined as a parameter

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‫to move platform, but we haven't actually passed it in as an argument to move platform in tick.

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‫And you'll see I've got a little red squiggly line here.

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‫If I hover over it, it says there's too few arguments in the function call because I have defined it

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‫in the header file and now in the C++ as well as requiring one parameter of type float.

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‫So I must provide that parameter.

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‫So I'm going to make sure that the parameter I'm providing, the value that I'm providing comes from

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‫the delta time variable or the Delta time parameter from tick.

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‫So with threading the value, the value gets passed into tick, then gets passed into MOVE platform

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‫and ends up in our parameter in the MOVE platform function where it can be used to execute our MOVE

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‫platform functionality.

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‫So I'd like you to create your own rotate platform function that we're going to call from TIC.

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‫So you're going to add it to the header file like we've done for our MOVE platform function.

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‫We're going to add it to the C++ file in the same way as well.

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‫So take your hints from the way we did it for those functions and then call it from the tick function.

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‫Make sure you pass in Delta time and you define any parameters to allow you to pass in the Delta time

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‫and implement the body of the Rotate platform so that it logs out a message.

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‫It's not actually going to rotate the platform yet, but as a placeholder to make sure that that is

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‫actually getting called print a log message using the UI log that we've learnt about.

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‫Pause the video and have a go.

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‫Okay.

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‫Welcome back.

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‫So we're going to start off in the header file and we're mostly going to be doing the same as we did

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‫for our MOVE platform.

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‫We're going to put it in a private section so that it's only accessible within our class.

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‫I'm going to give it a void return type, we're going to call it rotate platform.

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‫We're going to open up the parameter list.

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‫And in it we're going to put one parameter which is going to be a type float.

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‫We're going to call it Delta time and close the parameters and finish off with a semicolon.

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‫Now, most of what we do over in the C++ file is exactly the same as in the header file.

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‫So I'm actually going to copy this line, go over to the C++ file and show you what is different.

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‫So I'm going to go to a new empty line at the end of the file, paste it in, and then what's different

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‫is over here we need the scope resolution operator in the class name.

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‫So we're going to have a moving platform, colon, colon rotate platform.

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‫Then we have the parameter list and then we don't need the semicolon on the end.

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‫So remove the semicolon, add a new line and add our curly braces instead and a new line between those

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‫two curly braces.

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‫So what we want to do in here is print out a log message.

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‫So I'm going to type you log hit enter.

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‫It's just going to be a simple display message.

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‫And in the text I'm going to put the name of our platform.

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‫So it's going to be percents.

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‫Then we're going to type rotating dot and then I'm going to pass in the name.

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‫Now we could put this into a variable, but because it's quite a short line here, I'm just going to

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‫type star, get name and then put the parentheses so that we're calling essentially here calling the

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‫get name.

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‫That is the expression that gets hold of the F string.

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‫And then we are converting that result to put into our log message.

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‫So from all of our platforms, I'm expecting to see that rotating is printed, but this will only happen

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‫if I actually call it in tech.

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‫So let's go up to the tick function after MOVE platform can add a new line and call the rotate platform.

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‫And we need to you see, when I open up the parentheses, it gives me a hint that I need to pass in

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‫an argument for Delta time.

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‫So again, we're just going to pass that same Delta time variable from within here.

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‫And like I said, the names here don't have to be the same.

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‫So this delta time needs to match with the Delta time within tick.

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‫But we could choose to call the variable within rotate platform date instead and anywhere we use it

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‫within rotate platform, we'd have to use date the name of the parameter and the argument can basically

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‫be different.

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‫So let's hop over into unreal and hit compile because we've made some changes to the header file.

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‫The compilation will be slightly longer than when we just change the C++ file and once that's completed

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‫compiling, we're going to go ahead and hit play and open up the output log.

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‫And you can see that we are indeed displaying log messages about each of the platforms rotating.

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‫So it looks like our function is effectively getting called in tick.

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‫Great stuff.

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‫Now we understand how to create our own functions that are members of a class.

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‫It's very useful tool for reusing a code, but also for organizing it just like it was in Blueprint.

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‫I'll see you in the next lecture.