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‫Hello and welcome.

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‫In this lecture, we're going to be looking at how we can add dynamic text into our log messages using

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‫strings in C++.

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‫So let's dive in and learn about strings and C++.

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‫So we've seen how to print out some simple things from our UI log, but what if we wanted to print out

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‫some more text, something like the actor name, for example, or even something more complicated,

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‫such as a textual representation of a vector?

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‫Well, that does not typically have format specifiers because format specifiers have come to us from

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‫the age of C, which is a very basic programming language in comparison to C++.

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‫And so certain things just weren't thought up at the time.

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‫So things like vectors would not be included in the way that we format specify them.

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‫So we tend to use strings to do this.

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‫And as we've said in the past, strings are just text variables.

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‫They are variables that contain text so we can declare strings.

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‫In C++ we've used F vectors where we used vectors previously.

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‫Here we're going to use F string as the type for a string so we can have a string.

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‫And I'm just going to put in my string as the variable name for now.

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‫And how do we set a string value?

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‫Well, we've seen it a little bit around here already.

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‫These double quotes are what denote a string value in C++.

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‫So all of these expressions here, that one here where we've got the double quotes also over in the

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‫header file where we've got the double quotes for the category that is a string expression.

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‫So what we can do is set the my string variable from this and I'm going to say my string value just

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‫to give us an idea of that and put a semicolon at the end of the line and then how can we show this

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‫in a log statement?

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‫So I'm just going to remove the move distance from here as an argument to the log, and I'm going to

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‫change the text in the log message to say, here's my string colon.

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‫And then instead of the F specify, we use percent SSE this time to denote the string that we want to

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‫print out.

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‫And then the argument we pass into the E log function again between these two brackets is going to be

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‫my string.

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‫Now unfortunately that would be great if that just worked by itself.

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‫But unfortunately there's a little bit of a complication here in Unreal that they won't accept a straightforward

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‫string as an argument to the YUI log.

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‫It needs a little bit of a converting operator here, and the way we do this is by putting an asterisk

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‫in front of the my string and it just converts it from an F string into the format that it's looking

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‫for internally within the U log.

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‫We don't have to go into too much detail as to why it's doing this.

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‫It's it's beyond the level that we need to know at this point in time.

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‫I think it's just important to learn it as it is that when we do a percent se, we always need a star

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‫in front of our f strings.

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‫So let's see if that's worked by going over into Unreal and hitting the compile button.

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‫And then we're going to close down the live coding, hit play, open up the output log and here you

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‫go, here's my string, my string value.

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‫So it's printing out the value in the my string.

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‫But obviously this piece of code that I've just written is not particularly useful because well, I

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‫could have just written this string into here.

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‫Why bother with this whole substitution business?

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‫Well, where this gets more interesting is where we put a dynamic value into this variable instead.

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‫So we could do get name and call that.

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‫That is a function here available in the moving platform actor that gets the name of the actor that

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‫we see in the level out liner, we can put it into the variable.

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‫I'm going to call that variable name instead of my string and change its name down here in the US log

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‫as well.

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‫So then we can change the text of the log message to say begin play colon and then it's going to be

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‫the name of the actor.

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‫So let's go back into unreal, stop play, hit, compile, go ahead and hit play and open up the output

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‫log and you can see we get the messages begin play moving platform one begin play moving.

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‫Platform three pushing.

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‫Kub three pushing, keep five, pushing, keep seven.

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‫So we've got big in play and all the names of the different actors.

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‫Now this can be very useful because later on down the line where we're printing out our overshoot distance,

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‫it's not always clear who is overshooting in this case because they're all getting messed up together.

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‫So being able to print out the name of the actor that is producing the log message can be really helpful

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‫in pinpointing where a problem is.

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‫Happening.

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‫So I'd like to challenge you to log the name with that overshoot log so that we are going to see who

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‫has overshot and by how much.

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‫So you're going to add a variable for the name of the actor to tick like we did in Begin Play.

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‫You're going to get name into it and you're going to add a percent as specified somewhere anywhere you

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‫like into your log message where we're printing that overshoot and you're going to add an argument for

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‫that name.

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‫We still want the overshoot variable in the list of arguments, but after all, before that one, you're

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‫going to have to put the argument for the name as well.

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‫And it's important to hear that the order of the argument matches the order of the specifiers in your

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‫message.

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‫So if you put percents before percent f, then that's the order.

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‫The name should go before the overshoot or you should do it the other way round if you've done the other.

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‫And don't forget to add the star before your variable name to convert the string into something that

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‫the log you e log can use.

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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 by getting a variable and this isn't strictly necessary, but we are going

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‫to use the variable just for simplicity's sake and keeping that line a bit shorter.

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‫So we're going to have an F string called name using uppercase letters, usually to start our variable

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‫names.

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‫We're going to do a get name in to that variable and then we're going to use it as an argument.

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‫But where am I going to put my format, specify it in the log message?

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‫Well, I'm going to put it as the first thing in my log message to kind of make it clear that this is

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‫a log message coming from this thing.

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‫So I'm going to put percent s first, and that means that my argument needs to go before the overshoot

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‫argument.

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‫So we're going to get their name, put it in here, and we need to put an asterisk in front of the name

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‫in order to convert it appropriately.

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‫Now, let's go back into the editor.

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‫Stop playing hit recompile, close the terminal, hit play and open the output log.

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‫And you can see that we're starting to get our tick messages coming through.

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‫Got push and cube overshot by one push and q11.

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‫So you can see here you can make a conclusion that we couldn't make before, which is that the faster

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‫moving platforms, the pushing cubes are the ones overshooting by more, whereas the moving platforms

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‫seem to be overshooting by less, which is what I would expect.

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‫But it's good to see it confirmed here in the logs.

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‫Great stuff.

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‫So that's it for our little logging diversion.

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‫Hopefully you found this interesting and I will see you in the next lecture.