Blueprint Essentials: Arrays | 08 | v4.2 Tutorial Series | Unreal Engine

in this video I want to talk a bit about arrays now arrays are a special variable type that is actually more of a list than it is a single value they're very easy to create we're going to talk about how to create them here in just a few minutes but I want to get a few rules down about arrays before we move in so we've got probably one of the most important things is that all entries or all um all elements in within an array must be of the same type and the reason for that is that an array is really just a single variable that has a bunch of pieces of information in it an easy way to think of an array is like a series of mail boxes so we could just draw out some really quick boxes here and I'll try to keep this simple and we'd have to give this array a type and we already talked a bit about variable types in earlier video so let's say this was a string array and it could have names in it so we could have like Bob and Tom and Bill and cat and I don't even know so Zach because I have to be in there somewhere and Reggie because you know because it's Reggie so all of these must be at the same time these would all have to be strings it's not like you could remove Zach and have an object value in there like you couldn't stick some blueprint in there it would have to be actually a string value now so they must all be the same type next rule is that arrays are dynamic what that means is you can't set any any locked number of boxes or entries into your list that can change during gameplay so right now I have six names in my string array but there's nothing saying that during gameplay I couldn't add another box if I wanted to and put another name in there there's also nothing saying that I absolutely cannot remove an entry and have one fewer box so the number of entries within an array is not a locked thing so that makes them dynamic also arrays have index values and that's kind of like a way for the computer to know what entry in the array you're talking to now these are zero based which is important to keep in mind so in an array like this we'd have zero one two three and four so if you asked the array hey what's in entry 3 you'd get cat in this case so those are some rules to keep in mind about arrays now let's talk about how we create them so I'm going to jump over to unreal and I've got a very simple actor blueprint here that I'm going to create an array within so let's go ahead and click on the new variable button because again an array is just a type of variable so create that and let's give this a name we'll call this my string array and I'll set the variable type over to string and it's really this button right here at the very end that looks like a little colored grid line that is going to determine whether this is an array or not so when you see the little grid there that means it is an array if we compile this we can take a look down at the default values and we can start adding elements to the array so there you can see it has zero elements at the moment so we can hit the plus button add one so let's do let's see let's do some names again we'll do something totally unique that you've never heard of before and in no way is meant to represent anything you've ever heard of and we'll add another one all right so we have cambot gypsy Tom servo and crow again two four totally unique names we've probably never heard of in your life so what I'm going to do now is bring my array into the graph and I just want to show you a few things about working with arrays because again this is not a single value this is a list of multiple values that means a lot of the functionality a lot of the things that you typically do to single values will not work on an array unless you know how to work with them I'm going to talk briefly about that I'm going to do something a little bit hacky here I'm going to jump over to my defaults make sure that auto receive input is sets player zero just so that I can press buttons and make stuff happen let's right-click and I'll tap F and we'll make some things happen when I press the F key so let's drag out a wire into space and I'll type log and that's going to create a print string now this is a string array so at the top of your head maybe you might be thinking I should be able to just plug this in but the answer is no because the system has no idea which entry in the list you actually want to print out if you wanted to print everything then you would need to run a loop on this array looping is something that I'd like to talk about separately so we're going to keep things fairly simple for now I'm going to drag a wire off into space if you take a look under utilities and then under array you'll see that we have a for each loop and a for each loop with break again looping is something we're going to handle a little bit separately so jump under variables default and there's the entry for your actual array and then we can also call some functions so if you go under call function expand utilities there's some array functions here and this is where you can really start to work with your arrays and make changes to them so the tooltips are going to help you understand what each one of these things does for the array so you have things like a depend array which would again add an entire array to the end of your existing array some things that are probably really important for you to know would be like add and get so that will actually get a value from the array there's also last index versus length we'll talk about that a little bit more once we get into looping but a lot of folks want to know how many entries are in their array that would be length if you want to know the index value for the last entry in your array that would be last index so if you played with looping before perhaps in code or in scripting you would understand why you might actually want to use last index because it keeps you having to do length minus one when you're trying to perform a loop you don't get that don't worry that's something we'll talk about separately now I do want to mention you'll see that the little F's for function are color-coded in this case that has to do with pure versus impure functions so a green function is going to be pure a blue one is going to be impure all that means is that a green function is not actually going to affect the array while a blue one or an impure one really will so let's keep this simple we're going to grab a get and I want to unplug this for just a second to show you something notice that this node is completely gray it's not grayed out it's not like it's just not going to work for you the color coding on it disappears because this is actually a wild card value now you'll only see these really for the most part within arrays you see there's a the tooltip says array wildcard what that means is this is waiting for whatever type you plug into it and then it's going to work with that type really quickly I'm going to add a new variable and we'll call it my int array and I'll set its variable type over to integer and we'll just drag that into the scene really quick let's connect this up and you'll notice that my node turned that teal color so again this is just waiting for whatever type you plug into it now let's plug in a value between zero and three again we have four entries in our array right now so let's set that to three and we'll plug that into print string compile and we have a copy of the blue print in the level so I'll go ahead and hit play and if we hit F there you go you see we are printing out kro at the very end now that's about as far as I want to take things in this lesson just keep in mind that at any point you can drag out a wire and if you take a look under call function utilities array you'll see all the different things you can do to an array what I guess one other thing I could mention is there are several functions that you will perform that will output arrays and it's important to know that so as a really fast kind of way to wrap that up let me bring in several static meshes so here's a static mesh and we'll make a duplicate of that and a duplicate of that and let's grab all three of these guys and we'll make even more duplicates so we've got a total of six now meanwhile back over here in our graph let's nuke this stuff out we don't really need it and I'm going to right click and let's say actually let's do get all actors of class so we're going to say get all actors of class and what class are we looking for let's do static mesh actor and notice the output of this get all actors of class is an array so that's important to know because right now if we wanted to do anything to that array we'd have to get something out of it so we could say get and we could get something say at index 3 and now we have access to whatever mesh was in the third index there I will also point this out very very briefly before we go when when you have lists of actors like this or actor arrays you have a certain degree of functionality that you can perform on a for each basis so if we take a look actually let's go under our function suit so you can see call function for each and there's several different things we can do for example if we go under utilities and orientation we could say take the actor's local rotation and notice that was listed under for each that wasn't just listed under functions let me drag that out again so you can see that just to make sure so you have call function and you have call function for each and let's just take our delta rotation I'm going to drag backwards and say random rotator like so and just to show you what this is going to do I'm going to compile let's also make sure that here in our scene before I try anything that I set all of the mobility of these actors over to to mobile or moveable instead of static and now when I play if I hit F you see they all get random rotation that's because you're performing that function for each not all things not all things you might want to do not all functions have a for each version but I do want to point that out that that is available on certain output so that's all I want to talk about in this lesson over arrays thank you very much

Channel: Unreal Engine

Views: 101,704

Keywords: UE4, Blueprints, basics, essentials, variables, arrays, Unreal

Id: bGtQmuav748

Length: 11min 5sec (665 seconds)

Published: Wed May 28 2014