Decentralized Application (DApp) Architecture and Integration
Layers of a DApp
A DApp combines on-chain contracts with off-chain clients. The frontend talks to the chain through a provider (JSON-RPC or an injected wallet). Contracts expose an ABI; clients encode function calls and decode results and events. Indexers and subgraphs make historical queries efficient because reading logs directly is slow. Off-chain storage (IPFS or similar) holds large data referenced by content hashes.
Wallets and user flows
Understand account connection, network switching, transaction signing, and pending states. The user signs; the app never holds keys. Handle chain ID mismatch, rejected signatures, and insufficient funds gracefully. Distinguish read calls (no gas, no signature) from writes (gas, signature, confirmation).
Integration traps
Common errors include using stale ABIs after redeployment, hardcoding addresses instead of reading deployment artifacts, and assuming a transaction is final on submission. Another trap is treating event logs as ordered without confirming block depth, or forgetting that a wallet may switch accounts mid-session. Also watch decimal handling: token amounts use integer base units scaled by decimals, so mixing floats causes precision loss.
Rule of thumb
Wait for confirmations and re-read state after a transaction. Worked example: after a write, listen for the receipt, check status, then refresh balances from a read call rather than trusting local optimistic state.