IInventoryItemInterface

Module: InventoryPlugin
Header: IInventoryItemInterface.h
Base Class: UInterface
Type: Interface (Blueprint Native)

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Overview

IInventoryItemInterface defines a standard contract for any item that can be stored and managed within an inventory system.
Each function provides control over how the item interacts with an inventory component — allowing validation, interaction, and behavior customization when the item is used, dropped, or transferred.

This interface is BlueprintNative, meaning it can be implemented in both C++ and Blueprints.

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Functions

CanBeAddedToInventory(UInventoryComponentBase* InventoryComponent)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
bool CanBeAddedToInventory(UInventoryComponentBase* InventoryComponent) const;

Determines whether this item can currently be added to the specified inventory.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory attempting to add the item.

Returns:bool — true if the item can be added; false otherwise.

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CanBeRemovedFromInventory(UInventoryComponentBase* InventoryComponent)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
bool CanBeRemovedFromInventory(UInventoryComponentBase* InventoryComponent) const;

Checks whether the item can be removed from the specified inventory.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory attempting to remove the item.

Returns:bool — true if the item can be removed; false otherwise.

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CanBeTransferred(UInventoryComponentBase* InventoryComponent)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
bool CanBeTransferred(UInventoryComponentBase* InventoryComponent) const;

Determines if the item can be transferred to or from the specified inventory.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory involved in the transfer.

Returns:bool — true if the item is transferable; otherwise false.

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CanBeUsed(UInventoryComponentBase* InventoryComponent)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
bool CanBeUsed(UInventoryComponentBase* InventoryComponent) const;

Determines whether the item can be used within the specified inventory context. For example, some items may require the player to meet certain conditions before use.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory that owns the item.

Returns:bool — true if usable; false otherwise.

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CanBeDropped(UInventoryComponentBase* InventoryComponent)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
bool CanBeDropped(UInventoryComponentBase* InventoryComponent) const;

Checks if this item can be dropped from the specified inventory.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory that holds the item.

Returns:bool — true if droppable; otherwise false.

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OnUse(UInventoryComponentBase* InventoryComponent)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
void OnUse(UInventoryComponentBase* InventoryComponent);

Called when the item is used from a specific inventory. Implement the item’s use behavior here — such as applying an effect, consuming the item, or equipping it.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory that triggered the use action.

Example Use Cases:

• Consume a potion to restore health
• Equip a weapon or armor
• Trigger a special ability

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OnDrop(UInventoryComponentBase* InventoryComponent, int Quantity)

UFUNCTION(BlueprintNativeEvent, BlueprintCallable, Category = "Inventory|Item")
void OnDrop(UInventoryComponentBase* InventoryComponent, int Quantity);

Called when the item is dropped from an inventory.

Parameters:

Name	Type	Description
InventoryComponent	UInventoryComponentBase*	The inventory performing the drop action.
Quantity	int	The number of items being dropped.

Example Use Cases:

• Spawn a world pickup actor representing the dropped items
• Reduce the stack count in the inventory

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Implementation Notes

1. Inherit the Interface

class AMyItem : public AActor, public IInventoryItemInterface
{
    GENERATED_BODY()
    ...
};

2. Implement the Interface Methods

bool AMyItem::CanBeUsed_Implementation(UInventoryComponentBase* InventoryComponent) const
{
    return true; // Example: always usable
}

void AMyItem::OnUse_Implementation(UInventoryComponentBase* InventoryComponent)
{
    // Apply item effect or perform logic here
}

3. Expose to Blueprints

All functions are BlueprintCallable and BlueprintNativeEvent, meaning you can override them in Blueprint for flexible item logic without recompiling code.

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Blueprint Integration

Function	Callable in Blueprint	Can be Overridden	Notes
CanBeAddedToInventory	✅	✅	Validate adding to inventory
CanBeRemovedFromInventory	✅	✅	Define removal rules
CanBeTransferred	✅	✅	Manage ownership or exchange
CanBeUsed	✅	✅	Check use conditions
CanBeDropped	✅	✅	Handle drop logic
OnUse	✅	✅	Trigger use behavior
OnDrop	✅	✅	Spawn dropped items or visuals

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Example Implementation

A consumable item (e.g., a health potion):

bool AHealthPotion::CanBeUsed_Implementation(UInventoryComponentBase* InventoryComponent) const
{
    if (!InventoryComponent) return false;

    ACustomCharacter* OwnerCharacter = Cast<ACustomCharacter>(InventoryComponent->GetOwner());
    return OwnerCharacter && OwnerCharacter->GetHealth() < OwnerCharacter->GetMaxHealth();
}

void AHealthPotion::OnUse_Implementation(UInventoryComponentBase* InventoryComponent)
{
    if (ACharacter* OwnerCharacter = Cast<ACustomCharacter>(InventoryComponent->GetOwner()))
    {
        OwnerCharacter->RestoreHealth(50);
        InventoryComponent->RemoveItem(this, 1);
    }
}

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Last Updated: October 2025 Version: 1.1.0