On length changed function binding lets you know when an element added or removed from an array. This function pattern is only available for arrays.

Rules of Using OnLengthChanged_

  • The array must be declared as public(instance editable) on blueprints.

  • The function name must follow this format OnLengthChanged_ArrayName

  • Underscore character after OnLengthChanged is required.


  • Click on ADD NEW and then BLUEPRINT CLASS on the Content Browser

  • Pick Actor as parent class.

  • Rename the actor name as “SimpleActor”.

  • Click on the ADD COMPONENET under the Components tab. Search for the “ZDActor” and select the ZD ACTOR

  • Click ADD NEW then VARIABLE under My Blueprints tab.

  • Click on variable that you created, the Details panel will be shown in right side. Make it Array clicking pink bar on right-side of drop-down menu. Check Instance Editable.

  • Click ADD NEW  → FUNCTION on My Blueprint tab.

  • Rename function name as OnLengthChanged_StringArray.

OnLengthChanged_ function pattern must required.

  • Double click on OnLengthChanged_StringArray. Connect the node as shown in below. We set random integer between 0 and 42 to array element when array length changed(added a new element or deleted an element).

  • Click actor that you created. Therefore on click Add Item. When we added or removed an element on string array, array value automatically set on blueprints.