A Smart Contract that runs on Ethereum
This smart contract is written in Solidity and mimics a retail store. It supports customer and product registrations. A customer owns a simple cart to collect products before checking out.
In this early version there's no proper web interface available and you'll have to use truffle console to interact with the contract. In future I'll provide a proper app (maybe written in Angular 4.x as I don't like the default web-app environment provided by truffle).
| Name | Group | Signature | Usage | Returns |
|---|---|---|---|---|
| changeOwner | store | address | store.changeOwner(new_owner_address) | bool |
| registerProduct | store | uint, bytes32, bytes32, uint, uint | store.registerProduct(id, name, description, price, default_amount) | bool |
| deregisterProduct | store | uint | store.deregisterProduct(productId) | bool |
| getProduct | customer | uint | store.getProduct(productId) | (bytes32 prod_name, bytes32 prod_desc, uint prod_price, uint prod_default_amount) |
| registerCustomer | store | address, bytes, uint | store.registerCustomer(customerAddress, customerName, customerBalance) | bool |
| deregisterCustomer | store | address | store.deregisterCustomer(customerAddress) | bool |
| insertProductIntoCart | customer | uint | store.insertProductIntoCart(prodId) | (bool success, uint position_in_prod_mapping) |
| removeProductFromCart | customer | uint | store.removeProductFromCart(prod_position_in_mapping) | fires an event on successful removal |
| getCart | customer | store.getCart() | (uint[] productIds, uint completeSum) | |
| getBalance | customer | store.getBalance() | uint | |
| checkoutCart | customer | store.checkoutCart() | bool | |
| renameStoreTo | store | bytes32 | store.renameStoreTo(new_store_name) | bool |
First, activate a local test-blockchain with testrpc. If you don't have it just type npm install -g ethereumjs-testrpc and let NPM install it for you.
Second, go into the root of this project and execute truffle compile and truffle migrate (when changing the code during live-testing use truffle migrate --reset instead).
Third, jump into truffle's console with truffle console. Now you can use the local Blockchain to play with the Store 😄
I've created this project to learn a bit about Solidity & Ethereum. Expect no sophisticated code here. And lots of bugs.
Here's how I interact with it:
First, we'll need two addresses: a customer and a seller. By default testrpc registers ten Ethereum accounts at our disposal.
For more information about the namespace web3.eth consult truffle docs and also Ethereum JavaScript API.
var seller = web3.eth.accounts[0];
var customer = web3.eth.accounts[1];
We also need a reference to our Store.
var store;
We get this reference asynchronously by executing this snippet.
Store.deployed().then(d => store = d);
Now we register a new Customer with a certain amount of money. The original signature of registerCustomer in Solidity differs a bit from the one used below. This is because we want to execute this API from our seller account. All available API calls can be expanded by using similar options that let Ethereum know which account should pay for the execution of the code. As you already know the smart contracts don't get executed for free. You have to pay the miners. You can also set the amount of gas that can be used. More information regarding these options can be found here.
store.registerCustomer(customer, "Harris", 100, {from: seller});
Our customers will hopefully buy some of our products. Now let's register one by using registerProduct. Note that I'm not using {from: seller} here. By default truffle executes transactions under the first available account address. Only when we explicitely want to have a transaction being executed under a different address, like in the shopping cart checkout below, we'll have to provide it.
store.registerProduct(0, "t-shirt", "lacoste", 40, 1);
Now, as a customer we take a T-Shirt with id == 0 and put it into our cart.
store.insertProductIntoCart(0, {from: customer});
Let's see what's in the cart. Note that we don't execute a transaction here. A transaction would try to change the state on the blockchain that makes no sense in this case. Instead we execute a .call() that returns the product ids and total sum.
store.getCart.call({from: customer});
We also want to take care of proper event handling...
var allStoreEvents = store.allEvents().watch({}, '');
...by registering an event handler that'll siphon them all.
allStoreEvents.watch(function(err, res) { console.log("Error: " + err); console.log("Event: " + res.event); });
Let's try to check out. 😄
store.checkoutCart({from: customer});
Finally, let's see our balance after the checkout.
store.getBalance.call({from: customer});
The tests are written in Solidity. Simply enter truffle test in your console.
Many thanks to the nice Ethereum community from reddit.
Special thanks to cintix for the advice regarding unbounded iterations.