MulticastSparseDelegateProperty

Represents a multicast sparse delegate property in Unreal Engine.

MulticastSparseDelegateProperty wraps Unreal Engine’s FMulticastSparseDelegateProperty, which represents a multicast delegate that uses sparse storage. This is memory-efficient for delegates that are frequently unbound, as it stores only a 1-byte flag in the object and uses global storage for the actual invocation list.

Despite the different storage mechanism, the API is identical to MulticastDelegateProperty.

Accessing Delegate Properties

When you access a sparse multicast delegate property on a UObject, it returns a property wrapper object with methods to modify the delegate (identical API to inline multicast delegates):

local PlayerPawn = GetPlayerController().Pawn

-- Access delegate property (returns property wrapper)
local delegateProp = PlayerPawn.OnEndPlay

-- The wrapper has Add, Remove, and Clear methods
delegateProp:Add(MyCustomObject, FName("OnActorEndPlay"))

Methods

Add(targetObject, functionName)

Adds a delegate binding to the sparse multicast delegate’s invocation list.

Parameters:
- targetObject (UObject): The object to bind the delegate to
- functionName (FName | string): The name of the function to call on the target object

-- Access the delegate property wrapper
local prop = PlayerPawn.OnEndPlay

-- Add a delegate binding using FName
prop:Add(MyCustomObject, FName("OnActorEndPlay"))

-- Or use a string directly
prop:Add(MyCustomObject, "OnActorEndPlay")

Remove(targetObject, functionName)

Removes a specific delegate binding from the invocation list.

Parameters:
- targetObject (UObject): The object the delegate is bound to
- functionName (FName | string): The name of the bound function

-- Remove a specific binding
prop:Remove(MyCustomObject, FName("OnActorEndPlay"))

-- Or use a string
prop:Remove(MyCustomObject, "OnActorEndPlay")

Clear()

Removes all delegate bindings from the invocation list.

-- Clear all bindings
prop:Clear()

GetBindings()

Returns an array of all current delegate bindings.

Returns: Array of tables, where each table has Object (UObject) and FunctionName (FName) fields, or nil if no bindings exist

-- Get all current bindings
local bindings = prop:GetBindings()
if bindings then
    print("Delegate has", #bindings, "bindings")
    for i, binding in ipairs(bindings) do
        print(string.format("[%d] %s::%s",
            i,
            binding.Object:GetFullName(),
            binding.FunctionName:ToString()))
    end
end

Broadcast(…)

Fires the delegate, calling all bound functions with the provided parameters.

Parameters: Variadic - depends on the delegate’s signature function
Note: Parameters must match the delegate signature’s expected types and order

-- For a delegate with no parameters (e.g., Actor.OnEndPlay)
prop:Broadcast()

-- For a delegate with parameters
prop:Broadcast(25.0, CauserActor)

Implementation Details

FMulticastSparseDelegateProperty inherits from FMulticastDelegateProperty in the engine, so all the same vtable functions (AddDelegate, RemoveDelegate, ClearDelegate) are available and work identically.

Notes

Accessing Object.PropertyName for a sparse delegate property returns a property wrapper object, not the delegate values
The container object is implicitly stored in the wrapper, so you don’t need to pass it to methods
Both FName and string literals are accepted for function names
Storage mechanism is transparent to Lua - the API is identical to inline multicast delegates
Common example: Actor.OnEndPlay is a MulticastSparseDelegateProperty

UE4SS Documentation