Event Dispatchers vs Interfaces vs Casting
If you’re building gameplay in Unreal Engine 5.7 using Blueprints, sooner or later you hit the same problem in UE5 Blueprint communication: how do I make one Blueprint talk to another without turning my project into a web of hard references and failed casts? Communication is one of the biggest “make or break” topics for clean Blueprint architecture, especially once you have UI (UMG), interact systems, weapons, AI reactions, objectives, and multiplayer logic all touching the same gameplay events.
Most Blueprint projects start simple: you grab a reference, do a Cast To, call a function, and move on. That works—until it doesn’t. As your project grows, “just cast” turns into cast chains, UI updates get duplicated, and you end up with logic scattered across actors that shouldn’t even know each other exist. The good news is Unreal gives you a few core tools that cover almost every communication pattern you’ll need. The trick is picking the right one for the job so your systems stay readable, scalable, and easy to debug.
This post is meant to be a practical reference you can come back to when you’re stuck deciding between Event Dispatchers, Blueprint Interfaces, and Casting. By the end, you should be able to answer these quickly:
- Do I need one-to-many notifications or a direct call?
- Do I know the exact class, or do I just need “anything that can do X”?
- Am I building something that will scale to more actors and features later?
The quick decision rules
- Event Dispatcher = notify many listeners when one thing changes.
- Blueprint Interface = call the same behavior on many unrelated classes.
- Cast To = access class-specific data when you know the exact type.
- Direct Reference = call directly when the relationship is stable and intentional.
If you only remember one thing: Interfaces stop cast chains, Dispatchers stop polling, Casting is for known types.
Event Dispatchers (UE5 Blueprints)
Use when: you want to broadcast that something happened, and multiple listeners may respond.
What it is
An Event Dispatcher is an event defined on a Blueprint that other Blueprints can bind to at runtime. The owner of the dispatcher broadcasts it, and any bound listeners run their assigned events.
This is best thought of as a “subscription” model:
- The sender says: “I changed.”
- Listeners say: “Tell me when you change.”
What it’s best for
- UI updates (health, stamina, ammo, quest objectives)
- Global or shared gameplay events (wave started, match state changed)
- Systems where multiple things should react to one event (sound + VFX + UI + logic)
Why you’d choose it
- One-to-many is natural (you don’t have to manually call every listener)
- Sender stays decoupled (it doesn’t need to know who is listening)
What to watch out for
- Listeners still need a reference to the sender to bind.
- If you bind from something that can be destroyed (widgets, spawned actors), you must manage cleanup:
- Unbind when the listener is destroyed
- Unbind when switching targets (common in HUDs that track a “current” actor)
Typical example
- A Health Component broadcasts
OnHealthChanged(Current, Max) - HUD widget binds once and updates the bar/text whenever it fires
- No ticking, no polling, no “UI constantly checking health”
Blueprint Interfaces (UE5 Blueprints)
Use when: you want to call a function on something without caring what class it is, as long as it supports the behavior.
What it is
A Blueprint Interface is a set of function signatures (name + inputs/outputs). Any Blueprint that implements the interface agrees to provide the behavior. You call it using the interface function (Message) node, which safely calls the function if the object implements the interface.
This is best thought of as a “capability” model:
- The caller says: “If you can do X, do X.”
- The receiver decides what “X” means for it.
What it’s best for
- Interaction systems (Interact, Use, Examine)
- Damage or reaction systems across many actor types
- “Anything that can be activated/disabled” patterns
- Queries like “Give me interaction text” or “Can I open you?” (interfaces can return values)
Why you’d choose it
- Scales cleanly: add new interactables without changing the player logic
- Avoids cast chains completely
- Keeps code readable: one call instead of many “if it’s this class…”
What to watch out for
- Interface calls still require a reference (you must know what object you’re talking to)
- Message calls can fail silently if the object doesn’t implement it (great for flexibility, but when debugging, check with
Does Implement Interface)
Typical example
- Player line traces, gets Hit Actor
- Calls
Interact (Message)on the Hit Actor - Door/NPC/Loot all implement the same interface in their own way
Casting (Cast To) in UE5
Use when: you know the type (or expect a specific base class), and you need class-specific variables/functions/components.
What it is
Casting is a runtime type check. “Cast To BP_PlayerCharacter” means: if this object is BP_PlayerCharacter (or a child), give me a typed reference so I can access its specific members. If it isn’t, the cast fails.
What it’s best for
- Player-specific logic (you know you’re dealing with the player)
- Known class hierarchies (anything derived from a shared base enemy class)
- Situations where you truly depend on implementation details you didn’t generalize
Why you’d choose it
- Direct access to custom data/functions is fast and clear
- Very straightforward when the relationship is guaranteed
What to watch out for
- Overuse creates tight coupling and brittle systems
- The “cast chain” problem: casting to Door, then NPC, then Pickup, etc.
- If you find yourself casting just to ask “can you do X?”, that’s an interface problem, not a cast problem
Typical example
- Overlap happens, you only care if it’s the player
- Cast to BP_PlayerCharacter
- On success, apply effect / update something player-specific
Direct References (UE5 Blueprints)
Use when: there’s a stable relationship and you already have (or can set) a reference.
Direct reference isn’t a special Unreal feature—it’s simply storing an object reference variable and calling functions on it. In many projects this is the cleanest approach when the relationship is obvious.
Best for
- Character → current weapon
- Door → linked switch
- UI widget → owning player/controller
- Component → owning actor
What to watch out for
- Lifetime issues (validate references if actors can be destroyed)
- Over-coupling if you use direct references where a capability-based interface would scale better
A simple rule: if the relationship is “always this one thing,” direct reference is often perfect. If the relationship is “could be many kinds of things,” use an interface.
The “what should I use?” checklist
Ask these in order:
- Do I need multiple things to react to one change?
→ Event Dispatcher - Am I calling a shared behavior across many unrelated actor types?
→ Blueprint Interface - Do I need variables/functions that exist only on a specific class?
→ Cast To - Do I already have a stable reference and just need a direct call?
→ Direct Reference
Closing thoughts
Choosing the right Blueprint communication method early saves a lot of cleanup later. If you’re building a system that should scale, default to Interfaces for “do this if you can” interactions and Dispatchers for “something changed” notifications. Use Casting when the type is truly known and you need specific data, and use Direct References when the relationship is stable and intentional. When you’re unsure, start by asking whether you’re sending a notification, calling a capability, or accessing a specific class—your answer will usually point to the correct tool.