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Course 2 Project: Ethereum Smart Contracts, Tokens, and Dapps - Build CryptoStar Dapp on Ethereum

With Project 2, your focus moves from Bitcoin to Ethereum blockchain. You’ll begin by building a decentralized app (Dapp) that allows you to create, sell, and transfer ownership of unique star token (CryptoStar) on the Ethereum blockchain using smart contracts and the non-fungible (ERC721) token standard. This service is designed to demonstrate how to claim and transfer ownership of unique digital asset ( e.g. document, deed, agreement, media, etc.) on Ethereum blockchain.

You’ll build the back-end infrastructure for the CryptoStar with a pre-developed front end. This will enable you to render the service on any modern web clients.

For this project, you will create DApp notary service leveraging the Ethereum platform. You write smart contract that offer securely prove the existence for any digital asset - in this case unique stars and their metadata!

Project Instructions

Task 1 - Add Smart Contract Functions

Your Project is to Modify the StarNotary version 2 contract code to achieve the following:

SubTasks Details Status
1.1 Add a name and a symbol for your starNotary tokens. 👌
1.2 Add a function lookUptokenIdToStarInfo, that looks up the stars using the Token ID, and then returns the name of the star. 👌
1.3 Add a function called exchangeStars, so 2 users can exchange their star tokens...Do not worry about the price, just write code to exchange stars between users. 👌
1.4 Write a function to Transfer a Star. The function should transfer a star from the address of the caller. The function should accept 2 arguments, the address to transfer the star to, and the token ID of the star. 👌

Task 2 - Add supporting Unit Tests

Add supporting unit tests, to test the following:

SubTasks Details Status
2.1 The token name and token symbol are added properly. 👌
2.2 2 users can exchange their stars. 👌
2.3 Stars Tokens can be transferred from one address to another. 👌

Task 3 - Deploy your Contract to Rinkeby

Deploy your Contract to Rinkeby.

SubTasks Details Status
3.1 Edit the truffle.config file to add settings to deploy your contract to the Rinkeby Public Network. 👌

Task 4 - Modify the front end of the DAPP

Modify the front end of the DAPP to achieve the following:

SubTasks Details Status
4.1 Lookup a star by ID using tokenIdToStarInfo() (you will have to add code for this in your index.html and index.js files) 👌

Task 5 - Add a Readme.md file

The Readme.md file should include the following:

SubTasks Details Status
5.1 Your ERC-721 Token Name 👌
5.2 Your ERC-721 Token Symbol 👌
5.3 Version of the Truffle and OpenZeppelin used 👌

Helpful Links

Steps to Install the Environment

Node.js

Install a clean version of nodejs. I´m using the nvm (Node Version Manager) tool to allow install and switch between versions. Currently only version 10 of node.js works:

nvm install 10.22.1
nvm use 10.22.1

Truffle and other packets

install truffle, openzelepin, webpack and dependences:

npm i -g truffle
npm i --save openzeppelin-solidity
npm i --save truffle-hdwallet-provider
npm i -g webpack
npm i -g webpack-dev-server webpack-cli webpack-dev-middleware webpack-hot-middleware copy-webpack-plugin

To compile and run tests

For starting the development console, run:

truffle develop

For compiling the contract, inside the development console, run:

compile

For migrating the contract to the locally running Ethereum network, inside the development console, run:

migrate --reset

For running unit tests the contract, inside the development console, run:

test

For running the Front End of the DAPP, open another terminal window and go inside the project directory, and run:

cd app
npm run dev

Versions

Package Version
Truffle v5.1.48 (core: 5.1.48)
Solidity 0.6.12 (solc-js)
Node v10.22.1
Web3.js v1.2.1

As configured in truffle-config.js the smart contracts was compiled successfully using:

  • solc: 0.6.12+commit.27d51765.Emscripten.clang

Results

Unit Tests Terminal Output

truffle develop

Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.



  √ can Create a Star (140ms)
  √ lets user1 put up their star for sale (175ms)
  √ lets user1 get the funds after the sale (281ms)
  √ lets user2 buy a star, if it is put up for sale (305ms)
  √ lets user2 buy a star and decreases its balance in ether (273ms)
  √ 1.1 - can create a star with a name and star symbol properly, 1.2 lookup a star (157ms)
  √ 1.3 - can 2 users exchange their stars (436ms)
  √ 1.4 can a user transfer a star to other (162ms)

  8 passing (2s)

truffle(develop)>

To deploy in Brinkeby

Execute the command

truffle migrate --network rinkeby --reset

Deployment Terminal Output

PS C:\RIBAS\GITHUB\udacity-blockchaindev-nanodegree\project_2_CryptoStar_Dapp_on_Ethereum> truffle migrate --network rinkeby --reset

Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.



Migrations dry-run (simulation)
===============================
> Network name:    'rinkeby-fork'
> Network id:      4
> Block gas limit: 10000000 (0x989680)


1_initial_migration.js
======================

   Deploying 'Migrations'
   ----------------------
   > block number:        7353368
   > block timestamp:     1602457237
   > account:             0xa2944D405106c8251a69D6d22cfDB425055ec8EE
   > balance:             2.99855805
   > gas used:            144195 (0x23343)
   > gas price:           10 gwei
   > value sent:          0 ETH
   > total cost:          0.00144195 ETH

   -------------------------------------
   > Total cost:          0.00144195 ETH


2_deploy_contracts.js
=====================

   Deploying 'StarNotary'
   ----------------------
   > block number:        7353370
   > block timestamp:     1602457264
   > account:             0xa2944D405106c8251a69D6d22cfDB425055ec8EE
   > balance:             2.96876974
   > gas used:            2951493 (0x2d0945)
   > gas price:           10 gwei
   > value sent:          0 ETH
   > total cost:          0.02951493 ETH

   -------------------------------------
   > Total cost:          0.02951493 ETH

Summary
=======
> Total deployments:   2
> Final cost:          0.03095688 ETH

Starting migrations...
======================
> Network name:    'rinkeby'
> Network id:      4
> Block gas limit: 10000000 (0x989680)

1_initial_migration.js
======================

   Deploying 'Migrations'
   ----------------------
   > transaction hash:    0xed1f231bdc5a34d605f9aee87f58190d3edfe394506e295579ff08464cda970d
   > Blocks: 1            Seconds: 13
   > contract address:    0xee17d101Fb5446351D8f92D7EFABb1d982fE0899
   > block number:        7353371
   > block timestamp:     1602457310
   > account:             0xa2944D405106c8251a69D6d22cfDB425055ec8EE
   > balance:             2.99840805
   > gas used:            159195 (0x26ddb)
   > gas price:           10 gwei
   > value sent:          0 ETH
   > total cost:          0.00159195 ETH

   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.00159195 ETH


2_deploy_contracts.js
=====================

   Deploying 'StarNotary'
   ----------------------
   > transaction hash:    0x125ec7b3e85dd301b9013048c90f08904e57a5b6c2ce0ff6a71335966e7fa4e8
   > Blocks: 0            Seconds: 13
   > contract address:    0x267adBfc8D365ebFFC4EC6617807EEc33e3533F5
   > block number:        7353373
   > block timestamp:     1602457340
   > account:             0xa2944D405106c8251a69D6d22cfDB425055ec8EE
   > balance:             2.96756974
   > gas used:            3041493 (0x2e68d5)
   > gas price:           10 gwei
   > value sent:          0 ETH
   > total cost:          0.03041493 ETH


   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.03041493 ETH


Summary
=======
> Total deployments:   2
> Final cost:          0.03200688 ETH

Contract Address

contract address: 0x267adBfc8D365ebFFC4EC6617807EEc33e3533F5

Token Address

https://rinkeby.etherscan.io/token/0x267adbfc8d365ebffc4ec6617807eec33e3533f5

Transaction Hashes

transaction hash: 0x125ec7b3e85dd301b9013048c90f08904e57a5b6c2ce0ff6a71335966e7fa4e8

Frontend screenshots

alt text

Etherscan screenshots

https://rinkeby.etherscan.io/token/0x267adbfc8d365ebffc4ec6617807eec33e3533f5 alt text