This document provides an overview of smart contract development on Ethereum, including: 1) It describes the high-level architecture of Ethereum DApps and how they differ from traditional web apps. 2) It introduces useful tools for Ethereum development like testrpc, dapple, and truffle. 3) It walks through writing and deploying a simple smart contract in Solidity and interacting with it programmatically using Web3.

1. Ethereum Developers
Community
Smart Contract Tutorial
Arnold Pham
Cofounder of Lunyr
www.linkedin.com/in/arnoldpham
Unless otherwise stated, these slides are licensed under the Creative Commons Attribution-NonCommercial 3.0 License
(https://creativecommons.org/licenses/by-nc/3.0/us/)

2. High level view of web app client server architecture

3. High level view of Ethereum Dapp Architecture

4. Yikes! Downloading the whole blockchain?

5. EVM - Database and Code

6. Built in financial system

7. Solidity

8. Useful Tools - Opportunities for contribution
ethereumjs-testrpc
• Node.js based Ethereum client for testing and development
• Simulates full client behavior
• https://github.com/ethereumjs/testrpc
dapple
• developer multitool for managing the growing complexity of interconnected smart contract
systems
• https://github.com/nexusdev/dapple
truffle
• A development environment, testing framework and asset pipeline for Ethereum

9. Browser-Solidity

10. Shows errors

11. Creating Contracts

12. What is the ABI?
Application Binary Interface

13. Deploying a Contract with Web3

14. 1. Write your contract

15. 2. Make sure you have the Solidity compiler
No Solidity compiler? Proceed to next step
Download https://github.com/ethereum/solidity/releases

16. 3. Compile your contract with web3.eth.compile.solidity(source) to get an
object with the contract and compiler info

17. You need the abiDefinition

18. Create a contract object which can be used to
instantiate contracts on an address

19. Deploy the Contract
var contractInstance = MyContract.new([contructorParam1] [, contructorParam2], {data: '0x12345...', from: myAccount,
gas: 1000000});
Make sure to unlock the account first with personal.unlockAccount(eth.accounts[0])

20. Contract mined!

21. Check transactionHash

22. transactionHash: 0x87e42f5a325e13736342ce0d8e505e332b3ee20a5aa0c6f1080c0d5df8a0f1ab

23. You can also check that the contract was deployed at the address with:
eth.getCode(simplestorage.address)
Contract Address: "0xeb2186b9f667796497f0fc3c824d0bb57a548c25"

24. 1. Write your contract

25. Retrieving Data from the simplestorage Contract
instance
> simplestorage.get ()

26. Method calls with sendTransaction
contractInstance.method.sendTransaction([parameter], { from: eth.accounts[0])

27. Change storedData to 20. simplestorage.get() to
view change
> simplestorage.set.sendTransaction(20, {from: eth.accounts[0]})

28. Getting other people to interact with your code
Requires the ABI
Then they can instantiate a Javascript object which can be used to call the
contract from any node on the network
var newInstance = eth.contract(ABI).at(Address);

29. Deploying a Contract with Browser-Solidity

30. Write the contract in Browser-Solidity

31. Uses Metamask. Spend Ether to deploy it

32. Now on blockchain

33. Etherscan Block Explorer shows the contract

34. ERC20 Specification
Token Methods:
totalSupply
balanceOf
transfer
transferFrom
approve
allowance

35. Creating a simple token contract
(Warning: Very simplified Example)

36. The Token Contract

37. Steps to deploy the contract
> var tokenSource = 'contract Token{address public owner;mapping(address=>uint)balances;function
Token(){owner=msg.sender;balances[owner]=100;}function transfer(address _to,uint _value)returns(bool
success){if(balances[msg.sender]<_value){return false;}balances[msg.sender]-=_value;balances[_to]+=_value;return
true;}function getBalance(address _user)constant returns(uint _balance){return balances[_user];}}'

38. > var tokenCompiled = web3.eth.compile.solidity(tokenSource)

39. > var tokenContract = web3.eth.contract(tokenCompiled.Token.info.abiDefinition)

40. Create new instance

41. Check the owner

42. GetBalance

43. Transfer tokens to another address

44. Thank you for watching! Stay tuned for more!