Blueprint Essentials: While Loops | 13 | v4.2 Tutorial Series | Unreal Engine

in this video when I talked a little bit about while loops now while loops are something that you're probably not gonna use a whole lot in blueprint unless you start writing algorithms but I will give a kind of an academic demonstration of how to use one the way a while loop works is that it is going to constantly fire the loop body while a certain condition is true now you have to be a little bit careful with that because there they are a very easy way to crash your game because of that so if we do just like a simple print string and it doesn't really matter what it says and we just set condition to true this means that this is always going to fire because while the condition is true it's going to keep working and if we have hand coded or hard-coded the condition to true if we go ahead and jump back over to the game and hit play the moment I hit F we are going to freeze the game have to wait a few moments until it detects and out of range loop and suddenly the game dumps right back out so you generally don't want to do that that's gonna be a bad idea what I'm gonna do though is show you how to do something like store a certain number of random numbers into an array now again this is a pretty much just straightforward academic use of something like this but for starters let's make an array so I'll do a variable and we'll call this my int array make sure the variable type is set to end and make sure you hit the array button I'm going to bring this in as a getter and we are going to add a value to it so grab an array add node like so and we'll do that on the loop body now what are we gonna add well I'm gonna drag a wire backwards off the add node and we'll just say random and we will do a random integer with a max value of a thousand so we'll get a random number between zero and a thousand and we'll plug that into the array now again this would still kill right now it wouldn't do anything if we set this to true that would just go on through infinity so what we'll do is on our condition over here let's grab our interrogate and I'll hit get and we're going to do a length test on this there's the array length that's the number of elements in the array and we'll say if this is less than 20 well I don't know why I would punch the number in there it's bad habit so while it's less than 20 then the condition will be true and the loop will run as soon as that length hits 20 then the condition will be false and the loop will stop running so essentially what a loop what a while loop is doing is going to run whatever is connected to the loop body and then well actually let me let me rewind it's gonna start by checking the condition and if the condition is true then it'll run the loop body then it'll check the condition again and then they'll run the loop body if it's true so it just goes back and forth eventually the condition will be false at the moment that happens it will fire off the completed branch so with us constantly increasing the size of the array this will end but we're not going to see anything meaningful from it it's just going to store 19 random numbers and that'll be the end of it so what we will do is once we hit completed let's print out the contents of the array so I'll bring it another copy of the my int array let's do just a regular for loop let's do a for each right there and we'll plug our array into that and then to the loop body we will print so do a print string let's take our array element we'll plug that in that automatically gets converted so that we can see the numbers and then when that is done we will clear the array so it's going to erase whatever's in the array so fairly simple setup again it's just gonna check the condition and then just continue working so let's jump back and test so we'll hit play and I hit F and we get a stack of random numbers hit it again we get a different stack of random numbers and so on and so on and so on so it's really all there is to it you do have to be very very careful of the while loop you will probably not use it very often if really ever until you start doing things like writing algorithms and blueprint you probably won't need to use it very much in fact even in this case it would be a lot easier for me to run a for loop or at least a lot safer and a lot more difficult for me to run into a potential infinite loop problem but that's enough to get you started so that's going to wrap things up for this video thanks a lot

Channel: Unreal Engine

Views: 59,311

Keywords: UE4, Blueprints, basics, essentials, loops, while, Unreal

Id: 2RkaUkaLZu4

Length: 5min 1sec (301 seconds)

Published: Wed May 28 2014