Error: unreal engine cannot instantiate abstract class

Detailed Solution for "Unreal Engine Cannot Instantiate Abstract Class" Error

1. Understand Abstract Classes

• In Unreal Engine, an abstract class is a class that contains at least one pure virtual function.
• Abstract classes are designed to be used as base classes and cannot be directly instantiated.

2. Identify the Abstract Class

• Determine which class Unreal Engine is unable to instantiate by checking the error message.
• Note the name of the class and its inheritance hierarchy.

3. Review the Abstract Class

• Open the header file (.h) of the abstract class.
• Look for any pure virtual functions (functions ending with =0;) that have not been implemented.

4. Implement Pure Virtual Functions

• In the derived class that inherits from the abstract class, provide concrete implementations for all pure virtual functions from the base class.
• Use the override keyword in the derived class's function declarations to ensure that you're overriding the intended functions from the base class.

5. Check UCLASS Declaration

• Verify the UCLASS macro in your derived class header.
• Make sure it's not marked as Abstract. If it is, remove this unless you intend for the class to be abstract.

6. Compile and Test

• After making changes, recompile your code to ensure there are no compilation errors.
• Test the derived class to see if the "cannot instantiate abstract class" error has been resolved.

7. Verify Inheritance Hierarchy

• Double-check that all classes you're attempting to instantiate are meant to be instantiated and are not just there to provide a polymorphic interface for other subclasses.
• Ensure that the inheritance hierarchy is correctly set up and that there are no missing or incorrect overrides.

By following these troubleshooting steps and ensuring that all pure virtual functions are properly implemented in the derived class, you should be able to resolve the "cannot instantiate abstract class" error in Unreal Engine.