NotifyOnNewObject

The NotifyOnNewObject function executes a callback whenever an instance of the supplied class is constructed via StaticConstructObject_Internal by UE4.

Inheritance is taken into account, so if you provide "/Script/Engine.Actor" as the class then it will execute the callback when any object is constructed that's either an AActor or is derived from AActor.

The callback can return true to remove (unregister) that specific NotifyOnNewObject callback.

The provided class must exist before this calling this function.

Parameters

#	Type	Information
1	string	Full name of the class to get instance construction notifications for, without the type prefix
2	function	The callback to execute when an instance of the supplied class is constructed

Callback Parameters

#	Type	Information
1	UObject	The constructed object

Callback Return Value

#	Type	Information
1	boolean	If true, remove the current callback from listening to any more notifications

Example

NotifyOnNewObject("/Script/Engine.World", function(ConstructedObject)
    print(string.format("World Constructed: %s\n", ConstructedObject:GetFullName()))
end)

NotifyOnNewObject("/Script/Engine.Actor", function(ConstructedObject)
    print(string.format("Actor Constructed: %s\n", ConstructedObject:GetFullName()))

    -- Unregister this callback after the first actor is found,
    -- meaning this current function will only be called exactly once
    return true
end)

What NOT to do

Please don't duplicate the NotifyOnNewObject call for the same class multiple times, as it could cause performance issues if multiple mods are doing it (which has been seen in the wild).

For example, this:

NotifyOnNewObject("/Script/Engine.PlayerController", function(PlayerController)
    PlayerController.bShowMouseCursor = true
end)
NotifyOnNewObject("/Script/Engine.PlayerController", function(PlayerController)
    PlayerController.bForceFeedbackEnabled = false
end)
NotifyOnNewObject("/Script/Engine.PlayerController", function(PlayerController)
    PlayerController.InputYawScale = 2.5
end)
NotifyOnNewObject("/Script/Engine.PlayerController", function(PlayerController)
    PlayerController.InputPitchScale = -2.5
end)
NotifyOnNewObject("/Script/Engine.PlayerController", function(PlayerController)
    PlayerController.InputRollScale = 1.0
end)

should just be this:

NotifyOnNewObject("/Script/Engine.PlayerController", function(PlayerController)
    PlayerController.bShowMouseCursor = true
    PlayerController.bForceFeedbackEnabled = false
    PlayerController.InputYawScale = 2.5
    PlayerController.InputPitchScale = -2.5
    PlayerController.InputRollScale = 1.0
end)

UE4SS Documentation