Shop

The client sends which product. The server looks up the price, checks Money, then Set. Never let the client send the new balance or the price.

Catalog header

src/shared/constants/ShopCatalog.hpp

Cluaupp has no maps. A function with early returns is the catalog.

#pragma once

const int PRODUCT_HEALTH_PACK = 1;
const int PRODUCT_SPEED_TOME = 2;

int PriceOf(int productId) {
  if (productId == PRODUCT_HEALTH_PACK) {
    return 50;
  }
  if (productId == PRODUCT_SPEED_TOME) {
    return 200;
  }
  return 0;
}

PriceOf lives in a header so the server is the copy that matters. The client may include it for UI labels, but a patched client cannot change what the server charges.

Server — ShopServer.server.clpp

#include <clpp/roblox.clh>
#include <clpp/libs/sweep.clh>
#include <clpp/libs/net.hpp>
#include <clpp/libs/keep.clh>
#include "../../../shared/constants/ShopCatalog.hpp"

Janitor janitor = new Janitor();
NetEvent* Buy = Net::Event("Buy");

void ApplyProduct(Player player, int productId) {
  Model character = player.Character;
  if (character == null) {
    return;
  }
  Humanoid humanoid = character.FindFirstChildOfClass("Humanoid");
  if (humanoid == null) {
    return;
  }
  if (productId == PRODUCT_HEALTH_PACK) {
    humanoid.Health = humanoid.MaxHealth;
    return;
  }
  if (productId == PRODUCT_SPEED_TOME) {
    humanoid.WalkSpeed = 24;
    return;
  }
}

void OnBuy(Player player, int productId) {
  int price = PriceOf(productId);
  if (price < 1) {
    warn("unknown product " .: productId);
    return;
  }
  Data data = DataService.Server.WaitFor(player);
  if (data == null) {
    return;
  }
  int money = data.Get(DataService.Server.Paths.Currencies.Money);
  if (money < price) {
    post(player.Name .: " cannot afford " .: productId);
    return;
  }
  data.Set(DataService.Server.Paths.Currencies.Money, money - price);
  ApplyProduct(player, productId);
}

void init() {
  Buy.On(OnBuy);
  janitor.Add(Buy);
}

Debit before (or atomically with) the effect. If you grant the item first and the Set fails, the player dupes.

Client — ShopClient.client.clpp

#include <clpp/roblox.clh>
#include <clpp/libs/sweep.clh>
#include <clpp/libs/net.hpp>
#include "../../../shared/constants/ShopCatalog.hpp"

Janitor janitor = new Janitor();
NetEvent* Buy = Net::Event("Buy");

void OnHealthPackClicked() {
  Buy.FireServer(PRODUCT_HEALTH_PACK);
}

void init() {
  return;
}

Wire OnHealthPackClicked to a TextButton.MouseButton1Click.Connect(OnHealthPackClicked) when you have the GUI. The remote payload is only the product id.

Rules

• productId < 1 / unknown id → PriceOf returns 0 → reject.
• Do not FireServer(price) or FireServer(newMoney).
• Leaderstats updates from GetChangedSignal after Set.
• Same Net name "Buy" on both sides.

See Safety.