Implementing Multi-Step Input Triggers

Implementing Multi-Step Input Triggers

In this lesson, you will learn how to architect a "Combo System" that requires players to execute a specific sequence of button presses to trigger a special ability.

The Logic of Sequential Input

While standard Enhanced Input actions trigger immediately upon a button press, a multi-step trigger requires you to maintain a state machine. You track which step the player is currently on, and if they fail to provide the correct input within a narrow timing window, the sequence resets.

To implement this, you can define a TArray<EInputType> representing the required sequence and an integer CurrentStepIndex to track progress within your Character class.

Implementation Pattern

Each time the player triggers an InputAction, you compare the input against the expected element in your array:

void AMyCharacter::HandleComboInput(EInputType InputAction)
{
    if (InputSequence[CurrentStepIndex] == InputAction)
    {
        CurrentStepIndex++;

        if (CurrentStepIndex >= InputSequence.Num())
        {
            ExecuteSpecialAbility();
            CurrentStepIndex = 0; // Reset after success
        }
        else
        {
            // Start a timer to reset the combo if they take too long
            GetWorldTimerManager().SetTimer(ComboTimerHandle, this, &AMyCharacter::ResetCombo, 0.5f, false);
        }
    }
    else
    {
        ResetCombo();
    }
}

Managing State

When using Enhanced Input, you should bind your specific combo buttons (e.g., Light Attack, Heavy Attack) to this handler. By using a FTimerHandle, you enforce the "precise order" constraint, ensuring the player must perform the moves in quick succession. If the timer expires before the next input, ResetCombo() is called, forcing the CurrentStepIndex back to zero.

This pattern keeps your logic clean by separating the validation of the sequence from the execution of the ability. Remember to use UFUNCTION to expose these checks if you intend to trigger visual feedback—like combo-meter UI—via BlueprintImplementableEvent.

Key Takeaway: A multi-step trigger is essentially a state machine that tracks progress through an array of required inputs and resets that progress if the player inputs an incorrect button or exceeds a defined time limit.