Dapps

Dapps (decentralized applications) are user-facing apps that invoke Smart Contracts.

Tools

Truffle

Truffle is a CLI tool for developing dapps.

The dapps usually have the following project structure:

• {app-name}
  • {app-name}-contracts - stores smart contracts
  • {app-name}-app - stores the web app

Truffle commands:

• truffle init initializes a directory for smart contracts.
• truffle compile compiles Solidity files and creates a JSON file that represents the applicaton binary interface (ABI). It defines the interface that will be used to communicate between a web app and a smart contract.

Each contract needs to be specified in migrations script to be deployed.

• truffle migrate --reset - deploys smart contracts. The --reset redeploys existing contracts and it is a viable option only in developmnent. Production smart contracts are immutable.

Ganache

Ganache is a blockchain running locally for testing. It’s useful while developing dapps or smart contracts. It’s similar to what Remix IDE offers in the browser.

MetaMask

MetaMask is a wallet browser extension that allows to connect to the blockchain from the browser. It can be used in combination with Ganache for local development, or with real Ethereum networks as well.

Data Storage

Dapps, like traditional apps need to persist data. Dapps consist of:

• web app
• smart contracts

These two parts store data differently.

• web app stores data off-chain, in a database
• smart contact stores data on-chain, in the blockchain itself.

Tehe on-chain data should be kept to a minimum.