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NFT Inventory Loot

Overview

In this tutorial, you will learn how NFTs (Non-fungible Tokens) can be used as the loot that can be added to an inventory. You will learn how to read a player's wallet and a collection of your choice to build up a list of loot that will be compared against an inventory asset data table.

  • Completion Time: ~30 minutes
  • Knowledge Level: It is recommended to have completed the Creating Inventories tutorial.
  • Skills you will learn:
    • Reading a player's wallet using the Blockchain API.
    • Reading a collection using the Blockchain API.
    • Adding items to the player's inventory.

Find Contract Address

You can find a contract address by accessing one of the NFTs in the collection you want to pull from. On OpenSea when viewing an item in a collection, the URL will show some information that is useful to know and use.

For example, take Bag #6167 from the Loot collection. The URL contains the blockchain the token is on, the contract address, and the token ID.

https://opensea.io/assets/ethereum/0xff9c1b15b16263c61d017ee9f65c50e4ae0113d7/6167

This information can also be found in the Details section of the token page.

Info

Build Loot List

A loot list will be built in Lua that contains the items from the player's wallet and a collection. There are a few ways this can be done, but for simplicity, you will fetch one page of results from the player's wallet and one page of results from a collection.

The reason for the collection is if the player does not own any NFTs. Adding a page from the collection will make sure the player has a chance to receive something from the loot list.

Create GivePlayerLootServer Script

Create a new script called GivePlayerLootServer and place it into the Hierarchy. This script will be responsible for fetching the NFTs from the player's wallet, and NFTs from a collection you can specify.

Script

Add Variables

Add the following variables to the script. The collectionTokens table will hold all the tokens that were fetched from the collection. The tokens will be cached to this table to prevent fetching them again when another player joins the game. The fetching boolean will be set to true when the tokens for the collection are being fetched.

Set the contractAddress to either your own or from a collection online for testing.

local contractAddress = "" -- Your collection contract address to pull from.
local collectionTokens = {}
local fetching = false

Create FetchCollectionTokens Function

Create a function called FetchCollectionTokens. This function will fetch one page of tokens from the collection. Using GetTokens requires the contractAddress to be passed as the first argument.

Using GetResults on the tokens will return a table of tokens from the contract address that can then be used.

When calling GetTokens, script execution will be halted while the tokens are being fetched.

local function FetchCollectionTokens()
    fetching = true

    local tokens = Blockchain.GetTokens(contractAddress)

    collectionTokens = tokens:GetResults()
    fetching = false
end

Create GivePlayerLoot Function

Create a function called GivePlayerLoot. This function will give the player a random item from the lootList that is passed in. If the lootList length is 0, the function will return.

To give a random item to the player, math.random can be used by passing the total number of items in the lootList table as the argument. It will return a number between 1 and the total number of items in the lootList table. For example, if the number was 5, then the item variable will hold a reference to entry 5 in the lootList table.

To show what loot the player could receive, it is printed out to the Event log.

function GivePlayerLoot(player, lootList)
    if #lootList == 0 then
        return
    end

    local item = lootList[math.random(#lootList)]

    print("Receiving loot item:", item.name)
end

Create OnPlayerJoined Function

Create a function called OnPlayerJoined. This function will check to see if there are any tokens in the collectionTokens table. If there are none, and the server is currently not in the process of fetching them, it will call FetchCollectionTokens. While the tokens are being fetched, the function will be halted until fetching is false.

The next step to adding to the lootList is to also fetch the player's tokens. This can be done using the GetTokensForPlayer and passing the player as the first argument.

Because the tokens need to be part of a single list, the items from the collectionTokens can be added to the lootList. This will be done for each player that joins the game, they get the collection tokens and their tokens if they own any.

Finally, the GivePlayerLoot function is called by passing the player and lootList as arguments.

local function OnPlayerJoined(player)
    if #collectionTokens == 0 and not fetching then
        FetchCollectionTokens()
    end

    while fetching do
        Task.Wait()
    end

    local tokens = Blockchain.GetTokensForPlayer(player)

    local lootList = tokens:GetResults()

    for index, token in ipairs(collectionTokens) do
        lootList[#lootList + 1] = token
    end

    GivePlayerLoot(player, lootList)
end

Connect playerJoinedEvent

Connect the OnPlayerJoined so that it is called each time a player joins the game, which will print out the loot the player would receive.

Game.playerJoinedEvent:Connect(OnPlayerJoined)

The GivePlayerLootServer Script

GivePlayerLootServer 
local contractAddress = "" -- Your collection address to pull from.
local collectionTokens = {}
local fetching = false

local function FetchCollectionTokens()
    fetching = true

    local tokens = Blockchain.GetTokens(contractAddress)

    collectionTokens = tokens:GetResults()
    fetching = false
end

function GivePlayerLoot(player, lootList)
    if #lootList == 0 then
        return
    end

    local item = lootList[math.random(#lootList)]

    print("Receiving loot item:", item.name)
end

local function OnPlayerJoined(player)
    if #collectionTokens == 0 and not fetching then
        FetchCollectionTokens()
    end

    while fetching do
        Task.Wait()
    end

    local tokens = Blockchain.GetTokensForPlayer(player)

    local lootList = tokens:GetResults()

    for index, token in ipairs(collectionTokens) do
        lootList[#lootList + 1] = token
    end

    GivePlayerLoot(player, lootList)
end

Game.playerJoinedEvent:Connect(OnPlayerJoined)

Add Items to Inventory

Now that you know how to generate loot from the player's wallet or a collection, it would be useful to know how to connect the token to an inventory item. This will put the random loot into the player's inventory if there is space.

If you have finished the Creating Inventories tutorial, then you can use the inventory created from that tutorial for the second part of this tutorial. If you are using a different inventory, then some extra work on your part may be needed.

Connect Tokens to Inventory Items

When a random token is selected from the lootList, it needs to be verified that an item in the Inventory Assets is assigned to it.

Modify Inventory Assets Data Table

The Inventory Assets table will need a new column that contains the name of the token to match against.

  1. Open up the Inventory Assets data table from Project Content.
  2. Add a new column called loot_name which is a type of string.

Data Table

Add Loot Names to Rows

The next step is to link a token to the inventory item in the data table. Enter the name of the token as it appears in the collection. This will be compared against when the player joins the game. If there is a match in the data table, the player will receive that inventory item in their inventory.

In the image below, the loot_name column is filled for each row with the name of the token as it appears in the collection.

Loot Name

Update GivePlayerLootServer Script

The GivePlayerLootServer script needs to know about the Inventory API, so it can add an item to the player's inventory if there is a match.

In My Scripts in Project Content, find the InventoryAPI script and add it as a custom property to the GivePlayerLootServer script in the Hierarchy. Name the custom property InventoryAPI.

Property

Require the Inventory API

To use the Inventory API it will need to be required into the GivePlayerLootServer script first.

local INVENTORY_API = require(script:GetCustomProperty("InventoryAPI"))

Modify GivePlayerLoot Function

The GivePlayerLoot function needs to be modified to call a new function that will be added to the InventoryAPI script shortly.

A call to INVENTORY_API.AddLootItem will attempt to add the item to the player's inventory.

function GivePlayerLoot(player, lootList)
    if #lootList == 0 then
        return
    end

    local item = lootList[math.random(#lootList)]

    print(item.name)

    INVENTORY_API.AddLootItem(player, item)
end

The GivePlayerLootServer Script

GivePlayerLootServer 
local INVENTORY_API = require(script:GetCustomProperty("InventoryAPI"))

local contractAddress = "" -- Your collection address to pull from.
local collectionTokens = {}
local fetching = false

local function FetchCollectionTokens()
    fetching = true

    local tokens = Blockchain.GetTokens(contractAddress)

    collectionTokens = tokens:GetResults()
    fetching = false
end

function GivePlayerLoot(player, lootList)
    if #lootList == 0 then
        return
    end

    local item = lootList[math.random(#lootList)]

    print(item.name)

    INVENTORY_API.AddLootItem(player, item)
end

local function OnPlayerJoined(player)
    if #collectionTokens == 0 and not fetching then
        FetchCollectionTokens()
    end

    while fetching do
        Task.Wait()
    end

    local tokens = Blockchain.GetTokensForPlayer(player)

    local lootList = tokens:GetResults()

    for index, token in ipairs(collectionTokens) do
        lootList[#lootList + 1] = token
    end

    GivePlayerLoot(player, lootList)
end

Game.playerJoinedEvent:Connect(OnPlayerJoined)

Modify InventoryAPI Script

The InventoryAPI script needs to be modified. It will need a new function added that will fetch the current player's inventory and try to add the loot item passed into the function.

Add API.AddLootItem Function

Add a new function called API.AddLootItem. This function will check the player has an inventory and that the token passed in is not nil. It will then search through the ASSETS table to find an inventory item that matches the name of the token. If an item is found, then it will try to add the item to the player's inventory.

function API.AddLootItem(player, token)
    if API.PLAYERS[player.id] ~= nil and token == nil then
        return
    end

    local asset = nil
    local inventory = API.PLAYERS[player.id]

    for index, row in ipairs(ASSETS) do
        if row.loot_name == token.name then
            asset = row.asset
            break
        end
    end


    if asset ~= nil and inventory:CanAddItem(asset) then
        inventory:AddItem(asset)
    end
end

The InventoryAPI Script

InventoryAPI 
local ASSETS = require(script:GetCustomProperty("InventoryAssets"))
local INVENTORY = script:GetCustomProperty("Inventory")

local API = {}

API.PLAYERS = {}
API.INVENTORIES = {}
API.ACTIVE = {

    slot = nil,
    slotIcon = nil,
    slotCount = nil,
    slotIndex = nil,
    inventory = nil,
    hasItem = false

}

-- Server

function API.RegisterInventory(inventory)
    API.INVENTORIES[inventory.id] = inventory
end

function API.CreatePlayerInventory(player)
    local inventory = World.SpawnAsset(INVENTORY, { networkContext = NetworkContextType.NETWORKED })

    inventory:Assign(player)
    inventory.name = player.name

    API.PLAYERS[player.id] = inventory
    API.RegisterInventory(inventory)
end

function API.LoadPlayerInventory(player)
    local data = Storage.GetPlayerData(player)

    if data.inv ~= nil then
        for i, entry in ipairs(data.inv) do
            local item = API.FindLookupItemByKey(entry[1])

            if item ~= nil and API.PLAYERS[player.id]:CanAddItem(item.asset, { count = entry[2], slot = i }) then
                API.PLAYERS[player.id]:AddItem(item.asset, { count = entry[2], slot = i })
            end
        end
    end
end

function API.SavePlayerInventory(player)
    local data = Storage.GetPlayerData(player)

    data.inv = {}

    for i = 1, API.PLAYERS[player.id].slotCount do
        local item = API.PLAYERS[player.id]:GetItem(i)
        local entry = {}

        if item then
            local lookupItem = API.FindLookupItemByAssetId(item)

            if lookupItem ~= nil then
                entry = { lookupItem.key, item.count }
            end
        end

        table.insert(data.inv, entry)
    end

    Storage.SetPlayerData(player, data)
end

function API.RemovePlayerInventory(player)
    API.INVENTORIES[API.PLAYERS[player.id].id] = nil
    API.PLAYERS[player.id]:Destroy()
    API.PLAYERS[player.id] = nil
end

function API.MoveItemHandler(fromInventoryId, toInventoryId, fromSlotIndex, toSlotIndex)
    local fromInventory = API.INVENTORIES[fromInventoryId]
    local toInventory = API.INVENTORIES[toInventoryId]

    if fromInventory ~= nil and toInventory ~= nil then
        if fromInventory == toInventory then
            if fromInventory:CanMoveFromSlot(fromSlotIndex, toSlotIndex) then
                fromInventory:MoveFromSlot(fromSlotIndex, toSlotIndex)
            end
        else
            local fromItem = fromInventory:GetItem(fromSlotIndex)
            local toItem = toInventory:GetItem(toSlotIndex)

            local fromItemAssetId = fromItem.itemAssetId
            local fromItemCount = fromItem.count

            if toItem ~= nil then
                local toItemAssetId = toItem.itemAssetId
                local toItemCount = toItem.count
                local skipFromItem = false

                if toItemAssetId == fromItemAssetId then
                    local total = toItemCount + fromItemCount

                    if total > toItem.maximumStackCount then
                        if toItemCount == toItem.maximumStackCount then
                            toItemCount = toItem.maximumStackCount
                            fromItemCount = total - toItem.maximumStackCount
                        else
                            toItemCount = total - toItem.maximumStackCount
                            fromItemCount = toItem.maximumStackCount
                        end
                    else
                        skipFromItem = true
                        fromItemCount = total
                    end
                end

                fromInventory:RemoveFromSlot(fromSlotIndex)
                toInventory:RemoveFromSlot(toSlotIndex)

                if not skipFromItem then
                    fromInventory:AddItem(toItemAssetId, { count = toItemCount, slot = fromSlotIndex })
                end
            else
                fromInventory:RemoveFromSlot(fromSlotIndex)
            end

            toInventory:AddItem(fromItemAssetId, { count = fromItemCount, slot = toSlotIndex })
        end
    end
end

function API.RemoveItemHandler(inventoryId, slotIndex)
    local inventory = API.INVENTORIES[inventoryId]

    if inventory ~= nil then
        if inventory:CanRemoveFromSlot(slotIndex) then
            inventory:RemoveFromSlot(slotIndex)
        end
    end
end

function API.AddLootItem(player, token)
    if API.PLAYERS[player.id] ~= nil and token == nil then
        return
    end

    local asset = nil
    local inventory = API.PLAYERS[player.id]

    for index, row in ipairs(ASSETS) do
        if row.loot_name == token.name then
            asset = row.asset
            break
        end
    end


    if asset ~= nil and inventory:CanAddItem(asset) then
        inventory:AddItem(asset)
    end
end

-- Client

function API.ClearDraggedItem()
    API.ACTIVE.slot = nil
    API.ACTIVE.slotIcon = nil
    API.ACTIVE.slotCount = nil
    API.ACTIVE.slotIndex = nil
    API.ACTIVE.inventory = nil
    API.ACTIVE.hasItem = false
end

function API.SetDragProxy(proxy)
    API.PROXY = proxy
    API.PROXY_ICON = proxy:FindChildByName("Icon")
    API.PROXY_COUNT = API.PROXY_ICON:FindChildByName("Count")
end

function API.EnableCursor()
    UI.SetCanCursorInteractWithUI(true)
    UI.SetCursorVisible(true)
end

function API.DisableCursor()
    UI.SetCanCursorInteractWithUI(false)
    UI.SetCursorVisible(false)
end

function API.OnSlotPressedEvent(button, inventory, slot, slotIndex)
    local icon = slot:FindChildByName("Icon")
    local isHidden = icon.visibility == Visibility.FORCE_OFF and true or false
    local count = icon:FindChildByName("Count")

    -- Has item already.
    if API.ACTIVE.hasItem then

        -- No icon, so this is an empty slot, and dropping it into it.
        if isHidden then
            icon.visibility = Visibility.FORCE_ON
            icon:SetImage(API.PROXY_ICON:GetImage())
            API.ACTIVE.slot.opacity = 1
            API.ACTIVE.slotIcon.visibility = Visibility.FORCE_OFF
            count.text = API.ACTIVE.slotCount.text
            API.ACTIVE.slotCount.text = "0"

        -- Slot contains existing item
        else
            local item = API.ACTIVE.inventory:GetItem(API.ACTIVE.slotIndex)
            local toItem = inventory:GetItem(slotIndex)

            if(item ~= nil and toItem ~= nil and item.itemAssetId == toItem.itemAssetId and toItem.count == toItem.maximumStackCount) then
                API.ACTIVE.slot.opacity = 1
            else
                local tmpImg = icon:GetImage()
                local tmpCount = count.text

                icon:SetImage(API.ACTIVE.slotIcon:GetImage())
                count.text = API.ACTIVE.slotCount.text
                API.ACTIVE.slotIcon:SetImage(tmpImg)
                API.ACTIVE.slotCount.text = tmpCount
                API.ACTIVE.slot.opacity = 1

                tmpCount = nil
                tmpImg = nil
            end
        end

        Events.BroadcastToServer("inventory.moveitem", API.ACTIVE.inventory.id, inventory.id, API.ACTIVE.slotIndex, slotIndex)

        API.ClearDraggedItem()
        API.PROXY.visibility = Visibility.FORCE_OFF

    -- No item, pick up from clicked slot.
    elseif not isHidden then
        API.PROXY.visibility = Visibility.FORCE_ON
        API.ACTIVE.hasItem = true
        API.PROXY_ICON:SetImage(icon:GetImage())
        API.PROXY_COUNT.text = tostring(inventory:GetItem(slotIndex).count)
        slot.opacity = .6
        API.ACTIVE.slot = slot
        API.ACTIVE.slotIcon = icon
        API.ACTIVE.slotCount = count
        API.ACTIVE.slotIndex = slotIndex
        API.ACTIVE.inventory = inventory
    end
end

-- Shared

function API.FindLookupItemByKey(key)
    for i, dataItem in pairs(ASSETS) do
        if key == dataItem.key then
            return dataItem
        end
    end
end

function API.FindLookupItemByAssetId(item)
    for i, dataItem in pairs(ASSETS) do
        local id = CoreString.Split(dataItem.asset, ":")

        if id == item.itemAssetId then
            return dataItem
        end
    end
end

function API.RemoveItemSlotPressed()
    if API.ACTIVE.hasItem and API.ACTIVE.inventory ~= nil then
        Events.BroadcastToServer("inventory.removeitem", API.ACTIVE.inventory.id, API.ACTIVE.slotIndex)
        API.ACTIVE.slot.opacity = 1
        API.ACTIVE.slotIcon.visibility = Visibility.FORCE_OFF
        API.ClearDraggedItem()
        API.PROXY.visibility = Visibility.FORCE_OFF
    end
end

-- Events

if Environment.IsServer() then
    Events.Connect("inventory.moveitem", API.MoveItemHandler)
    Events.Connect("inventory.removeitem", API.RemoveItemHandler)
end

return API

Test the Game

Test the game to see if a random item is added to the inventory. This could take quite a few tries depending on how many items are in the wallet and collection. The more items in the inventory asset table that are linked to a token, the more chance an item will be added to the inventory.

Summary

The Blockchain API opens up new ideas for how your game can be played, and how players are rewarded. This tutorial shows you how easy it is to reward players with items from their Wallet. This could also be your own generated NFTs that players can purchase from your collection.

Learn More

Blockchain API | Inventories Reference | Creating Inventories Tutorial | Inventory API

Last update: June 2, 2022