Hello friends,
I want to do something in Unreal Engine, but I couldn’t figure out how to make it work. I have two different Blueprints: BP_Trigger and BP_Light.
What I want to achieve is:
How can I set up this connection? I would be very grateful if you could help me.
Thanks in advance! 
Hey @besT_Melik!
The item blueprint:
The area blueprint:
The character blueprint:
And here’s the result 
Hope this helps! 
This is the type of cases that would benefit from Blueprint Interfaces or Event Dispatchers. The blueprints don’t need to know about each other’s existance or cast to anything.
Create a Blueprint Interface and name it something like BPI_Interact.
Open the created interface and on the top right side create a function. Name it something like Interact. You don’t need to do anything else. Save and close the BPI_Interact.
Open your character blueprint and on the Class Settings, go to the Details panel and scroll down to the Interfaces section. Under the Implemented Interfaces click the Add button and select BPI_Interact.
Compile and save. Now open your BP_Trigger and do the same, and in your BP_Light also.
Open your BP_Trigger and create an array of the type Actor. Make it Instance Editable and Expose on Spawn. This will allow you to select various BP_Light actors from the world Outliner or the Viewport directly, so one Trigger will be able to activate as many lights as you want, or any Actor, and as long as they implement the interface you can have multiple actors doing something at the same time.
Now, on your ActorBeginOverlap event, from the Other Actor pin drag and get Does Class Implement Interface node and promote the boolean to a variable.
On your ActorEndOverlap, just set that variable to false.
Given that all of them implement the interface, in your BP_Trigger under your Functions section, should appear an Interfaces section. You will see the function you just created on your Interface. Right click on it and select Implement Event. It will create a new event and you will notice a small arrowed blueprint icon on the top right of the event node. This means it’s an Interface event.
Now drag your Actor type array and into a for each loop call the function Interact on the BPI Interact section and connect your looped Actor to the Target pin on the Interact function. Use a Branch with the boolean you promoted earlier to know if it’s Overlapping, therefore, it can interact or not.
Open your BP_Light and implement the Interact Interface Event. Now it’s up to you what the actions will be. You could use a boolean to keep track of the status of the light, or a FlipFlop, or whatever method you decide.
Open your character blueprint.
In your OnActorBeginOverlap get the Other Actor and promote it to a variable.
in your OnActorEndOverlap just set that variable to None/Empty.
From your Key F Event, add an IsValid? node and connect the Actor variable you created before, and from the True pin just call the Interface Event under BPI Interact and connect the Actor variable to the Target pin on your Interact function. If there’s a valid Actor that implements the BPI, it will send the message, and if there’s no Actor stored in the variable, it will do nothing if you press the action button, or you could use the action button to do something else if there’s no valid actor for your interaction, i.e. press it to reload a weapon or heal the character if it’s not inside the trigger area for the interactive Actor/s. The IsValid? node helps you avoid undesired behaviours and crashes if there’s a Null Pointer (None/Empty).
That’s all you need. You don’t need to Cast, or hard reference anything.
