Ethereum smart contract tutorial pdf
Developed on the top of the EVM, it is similar to the object-oriented programming language that uses class and methods. It allows you to perform arbitrary computations, but it is used to send and receive tokens and store states. It would be best to have a good understanding of Solidity programming language to efficiently write an Ethereum Smart Contract. What is a Smart Contract? Smart Contracts are the business logic or a protocol according to which all the transactions on a Blockchain happen.
We need to develop smart contracts according to which all the calculations on our token would happen. It is a stand-alone script written in Solidity and compiled into JSON and deployed to a particular address on the blockchain. Just like we can call a URL endpoint of a RESTful API to run some logic through an HttpRequest, we can execute deployed smart contract similarly at a particular address by entering the accurate data along with Ethereum to call the compiled and deployed Solidity function.
It can also be defined as a collection of code stored in the blockchain network, defining conditions to which all parties within the contract should agree. We will be sharing the example of Ethereum smart contract creation using the Solidity programming language.
So, it is first essential to understand what is Solidity. What is Solidity? Solidity is a Javascript-like language developed specifically for creating smart contracts. It is typed statically and supports libraries, inheritance and complex user-defined types. Solidity compiler converts code into EVM bytecode which is sent to the Ethereum network as a deployment transaction. It allows you to interact with smart contracts and dApps on the web without downloading the blockchain or installing any software.
Though MetaMask is currently available for Google Chrome browser, it is expected to launch for Firefox too in the coming years. Download MetaMask chrome extension before you start writing smart contracts. Once it is downloaded and added as a Chrome extension, you can either import an already created wallet or create a new wallet. You must have some ethers in your Ethereum wallet to deploy Ethereum smart contract on the network. Once it is installed, click on its icon on the top right of the browser page.
Clicking on it will open it in a new tab of the browser. It will ask you to create a password. After you create a password, it will send you a secret backup phrase used for backing up and restoring the account. Do not disclose it or share it with someone, as this phrase can take away your Ethers. You should either write this phrase on a piece of paper securely or store it safely on an external encrypted hard drive where no one could find it. Step 3: Add some dummy Ethers to your wallet In case you want to test the smart contract, you must have some dummy ethers in your MetaMask wallet.
For example, if you want to test a contract using the Robsten test network, select it and you will find 0 ETH as the initial balance in your account. You can add as many Ethers you want to the test network. For example, I have added 1 ETH in this scenario. Once the dummy ethers are added to the wallet, you can start writing smart contracts on the Remix Browser IDE in the Solidity programming language. The remix is the best option for writing smart contracts as it comes with a handful of features and offers a comprehensive development experience.
It is usually used for writing smaller-sized contracts. Step 5: Create a. Wait until the transaction is complete. After the transaction commits successfully, the address of the smart contract would be visible at the right-hand side of the remix window. At first, all the ERC20 tokens will be stored in the wallet of a user who is deploying the smart contract. To check the tokens in your wallet, go to the metamask window, click add tokens, enter the smart contract address and click ok.
You would be able to see the number of tokens there. Steps to test an Ethereum smart contract Try to run all your smart contract methods like transfer, total supply, and balance in the above smart contract example. These methods are present at the right-hand side of the remix window and you can run all the processes from there itself. Since we set the solidity version of our compiler to 0.
When writing or initializing a transaction, you have to pay for the transaction to be written to the blockchain. To make this work, you need to pay gas which is the fee or price required to successfully conduct a transaction and execute a contract on the Ethereum blockchain. As long as you are only reading from the blockchain and not changing or updating anything, you don't need to carry out a transaction and there will be no gas or cost to do so.
The function you call is then carried out only by the node you are connected to, so you don't need to pay any gas and the read is free. From our React app, we will interact with the smart contract using a combination of the ethers. What is an ABI? ABI stands for application binary interface. You can think of it as the interface between your client-side application and the Ethereum blockchain where the smart contract you are going to be interacting with is deployed.
ABIs are typically compiled from Solidity smart contracts by a development framework like Hardhat. To do so, go to the command line and run the following command: npx hardhat compile Now, you should see a new folder named artifacts in the src directory.
To deploy to the local network, you first need to start the local test node. To do so, open the CLI and run the following command: npx hardhat node When we run this command, you should see a list of addresses and private keys. These are 20 test accounts and addresses created for us that we can use to deploy and test our smart contracts. Each account is also loaded up with 10, fake Ether. In a moment, we'll learn how to import the test account into MetaMask so that we can use it. Next, we need to deploy the contract to the test network.
When the contract was deployed, it used the first account that was created when we started the local network. If you look at the output from the CLI, you should be able to see something like this: Greeter deployed to: 0x9fEd2D9a65FFdE9f3c7fa6e0 This address is what we will use in our client application to talk to the smart contract.
Keep this address available as we will need to use it when connecting to it from the client application. To send transactions to the smart contract, we will need to connect our MetaMask wallet using one of the accounts created when we ran npx hardhat node. We can import this account into MetaMask in order to start using some of the fake Eth available there.
Once the account is imported, you should see the Eth in the account: Now that we have a deployed our smart contract and set up our account, we can start interacting with it from the React app. From there, you can take it and make it look good if you'd like. With that being said, let's review the two objectives that we want from our React application: Fetch the current value of greeting from the smart contract Allow a user to update the value of the greeting So how do we accomplish this?
Web3Provider window. Contract greeterAddress, Greeter. You should also be able to make updates to the greeting by signing the contract with your MetaMask wallet and spending the fake Ether. How to Deploy and Use a Live Test Network There are several Ethereum test networks like Ropsten, Rinkeby, or Kovan that we can also deploy to in order to have a publicly accessible version of our contract available without having to deploy it to mainnet.
In this tutorial we'll be deploying to the Ropsten test network. To start off, first update your MetaMask wallet to connect to the Ropsten network. Next, send yourself some test Ether to use during the rest of this tutorial by visiting this test faucet.
We can get access to Ropsten or any of the other test networks by signing up with a service like Infura or Alchemy I'm using Infura for this tutorial. To deploy to the test network we need to update our Hardhat config with some additional network information. One of the things we need to set is the private key of the wallet we will be deploying from. To get the private key, you can export it from MetaMask.
I'd suggest not hardcoding this value in your app but instead setting it as something like an environment variable. Next, add a networks property with the following configuration: module. You should be now able to view the live contract on Etherscan Ropsten Testnet Explorer How to Mint Tokens One of the most common use cases of smart contracts is creating tokens. Let's look at how we can do that. Since we know a little more about how all of this works, we'll be going a little faster.
In the main contracts directory, create a new file named Token. Next, update Token. We will be covering ERC20 tokens later. This contract will create a new token called "Nader Dabit Token" and set the supply to To do so, let's update the client code we will need in order to make this work: import '.
Contract tokenAddress, Token. Now the tokens should be available in your wallet: Next, let's try to send those coins to another address. To do so, copy the address of another account and send them to that address using the updated React UI. When you check the token amount, it should be equal to the original amount minus the amount you sent to the address.
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