ExposeOnSpawn

The ExposeOnSpawn specifier exposes a property as a node pin when constructing the containing class. This allows for terse construction in Blueprints using only a single construct node, as opposed to first constructing the object and then setting properties individually. For example, consider the following property contained within a UserWidget class:

UPROPERTY(BlueprintReadOnly, meta=(ExposeOnSpawn="true"))
UTowerAction* Action;

When the UserWidget class is created, the Action property is exposed for initialization:

Notwithstanding its name, this specifier can be applied to properties of both Actors (which are spawned) and Objects (which are constructed).

Given that the decorated property is exposed on a Blueprint node, this specifier must be coupled with either of the BlueprintReadOnly or BlueprintReadWrite specifiers. If it is marked BlueprintReadOnly, the property can still be initialized on spawn but cannot be written within Blueprints thereafter.

The behavior of this specifier is unclear with respect to Delegates. For further information, see this article and UE-44977.

To achieve similar behavior when spawning actors or constructing objects from C++, check out SpawnActorDeferred.