Pickups

11 - Pickups

Pickups are plain entity scripts that compare distances every frame. For a nicer look, add BobAndSpin to the same Entity.

Collected items are recorded in the shared Global table so any other script (a door, the HUD, an exit) can react:

Key	Meaning
Global.coins	Number of coins collected
Global.keys[name]	true once the key called name has been collected

---

Pickup (health, coin, or key)

Attach to: the item Entity.

-- Scripts/Pickups/Pickup.lua (entity script)
public Entity player = nil
public enum(Health, Coin, Key) kind = Health
public number amount = 25
public string keyName = "red"
public number pickupRadius = 14

local KIND_HEALTH, KIND_COIN, KIND_KEY = 0, 1, 2

local transform

-- Returns true if the pickup was used up. It stays in the world if it wasn't.
local function Apply()
    if kind == KIND_HEALTH then
        local health = player:GetScript("Health")
        if not health.isValid or health.currentHealth >= health.maxHealth then
            return false   -- already at full health, leave it for later
        end

        health:Heal(amount)
        Debug.Print("+" .. amount .. " health")
        return true

    elseif kind == KIND_COIN then
        Global.coins = (Global.coins or 0) + amount
        return true

    elseif kind == KIND_KEY then
        Global.keys = Global.keys or {}
        Global.keys[keyName] = true
        Debug.Print("Picked up the " .. keyName .. " key")
        return true
    end

    return false
end

function Start()
    transform = entity.transform

    if player == nil then
        Debug.LogWarning("Pickup " .. entity.name .. " has no player assigned")
    end
end

function Update()
    if player == nil or not player.isValid then return end

    local p = player.transform.position
    local me = transform.position
    local dx, dz = p.x - me.x, p.z - me.z

    -- Flat distance, so a height difference doesn't count against the radius.
    if math.sqrt(dx * dx + dz * dz) > pickupRadius then return end

    if Apply() then
        local sound = entity.audioSource
        if sound ~= nil then sound:Play() end

        entity:Destroy()
    end
end

Notes

• Health pickups are only consumed if the player actually needs the health.
• Global.coins = (Global.coins or 0) + amount works even before anything has created the counter, since a missing value is nil and nil or 0 is 0.
• Destroying the Entity also removes its AudioSource, so the sound may be cut off. If that happens, play the pickup sound from an AudioSource on the player instead.
• Enum options are numbered from 0 in the order they appear in the annotation, which is why the KIND_... constants match enum(Health,Coin,Key).

---

Coin counter (HUD)

Attach to: a UI Entity with a UIText component.

-- Scripts/Pickups/CoinCounter.lua (entity script)
local label
local shown = -1

function Start()
    label = entity.uiText

    if label == nil then
        Debug.LogError("CoinCounter: " .. entity.name .. " has no UIText")
        return
    end

    Global.coins = Global.coins or 0
end

function Update()
    if label == nil then return end

    local coins = Global.coins or 0

    -- Only touch the text when the number changes.
    if coins ~= shown then
        shown = coins
        label.text = "Coins: " .. math.floor(coins)
    end
end

Notes

• Writing UI text every frame works, but only assigning it when the value changes is cheaper and is a good habit.
• math.floor makes 25.0 print as 25.