Best way to create a Finite State Machine on blueprints?

Development Programming & Scripting Blueprint
7

Typically I have a function to check whether an action can be done given current states.

For example, Fire input/event → Can I Fire (function) return: bool → Branch → (true) → fire action → set state

In the conditional function I’ll check if:

  • Is equipped (actually has a weapon equipped)
  • Current weapon obj is valid
  • ammo > 0
  • not falling
  • not in swimming state
  • and many other bools/states etc.

It can be a tedious process, but it has to be done. I always start out by determining “what should prevent this action from occurring”. I set up all the needed conditional vars. Then write my If statements.

Take a look at the Character Movement Component (CMC) Jump and Crouch/UnCrouch functions.

https://github.com/EpicGames/UnrealEngine/blob/release/Engine/Source/Runtime/Engine/Private/Components/CharacterMovementComponent.cpp

example: Jump line 877

bool UCharacterMovementComponent::DoJump(bool bReplayingMoves)
{
	if ( CharacterOwner && CharacterOwner->CanJump() )
	{
		// Don't jump if we can't move up/down.
		if (!bConstrainToPlane || FMath::Abs(PlaneConstraintNormal.Z) != 1.f)
		{
			Velocity.Z = FMath::Max(Velocity.Z, JumpZVelocity);
			SetMovementMode(MOVE_Falling);
			return true;
		}
	}
	
	return false;
}

bool UCharacterMovementComponent::CanAttemptJump() const
{
	return IsJumpAllowed() &&
		   !bWantsToCrouch &&
		   (IsMovingOnGround() || IsFalling()); // Falling included for double-jump and non-zero jump hold time, but validated by character.
}

UnCrouch starts on line 2703

void UCharacterMovementComponent::UnCrouch(bool bClientSimulation)
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