2.5 - Child Blueprints

blueprint_advanced_2_5.png

It is possible to create a child Blueprint based on a parent Blueprint, similar to the way you would create a Material Instance of a master Material. The children automatically inherit the functionality of their parent, which can then be augmented, added to, or altered. In this example, the three collectible pickup Blueprints are children of a generic pickup Blueprint.

The parent Blueprint is BP_Pickup_Parent_C, and the three child Blueprints are:

  • BP_Pickup_Child_Health

  • BP_Pickup_Child_Coin

  • BP_Pickup_Child_Cupcake

Parent Blueprint's Event Graph

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The parent Blueprint, BP_Pickup_Parent, contains script for basic pickup behavior, such as a timeline animation to make the pickup spin and float, and a sequence for collecting the pickup. The child Blueprints inherit all of this script, but have additional script for when they are collected, so that each pickup does something different while sharing the same basic features. This is useful because any updates made to the parent Blueprint's script will also apply to all its child Blueprints.

The OnPickedUp event dispatcher is called when the player's Pawn overlaps the Pickup Trigger SphereComponent. Each child Blueprint binds a different event to OnPickedUp, so that a different string prints when the player collects each pickup and OnPickedUp is called.

Child Blueprints' Event Graph

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As a rule, Blueprint graphs cannot contain duplicates of the same event, so if both the parent script and the child script each contain a ReceiveBeginPlay event, only the event in the parent script will fire. You can get around this in the child script by right-clicking an event and selecting Add call to parent function. This will create a function that will trigger the corresponding event in the parent script when it is called.