16 Essential Tips for Writing High-Quality Smart Contracts

What Is a Smart Contract?

A smart contract is a self-executing program that encodes agreement terms on a blockchain. It facilitates transactions by receiving, storing, and transferring value autonomously. Smart contracts underpin blockchain application development and influence three core transaction phases:

1. Transaction Construction: Requires contract deployment (via binary encoding) and function calls (using ABI interfaces).
2. Transaction Execution: Relies on binary instruction sets extracted from deployed contracts.
3. Consensus & Validation: Executed across all blockchain nodes for immutability.

Smart Contract Types on FISCO BCOS

1. Solidity Contracts

• Pros: Mature ecosystem, robust functionality.
• Cons: Steep learning curve, EVM performance bottlenecks, coupled data/logic.

2. Precompiled Contracts (CRUD-Based)

• Pros: Database-like operations, high throughput (~5x faster than Solidity), decoupled storage.
• Cons: Platform-specific, best for simple logic (e.g., notary services).

16 Expert Techniques

Security

1. Encrypt Sensitive Data: Use hashing/ZKP for privacy (e.g., store contract hashes, not raw terms).
2. Limit Visibility: Prefer internal over public functions for inherited modifiers.
3. Boundary Checks: Add require() for arithmetic (e.g., prevent uint8 overflow).
4. Use Security Tools: Slither/Securify for vulnerability scans.

Performance

5. Offload Heavy Calculations: Move complex math off-chain.
6. Minimize On-Chain Data: Store only critical business fields.
7. Reduce Cross-Contract Calls: Use structs to consolidate data.
8. Leverage Inheritance: Compile-time code inclusion avoids runtime calls.
9. Optimize Storage: Use mapping for O(1) lookups (trade storage for speed).
10. Variable Packing: Group sub-32-byte variables into single slots.
11. Use view/pure: Mark read-only functions to skip consensus.

Extensibility

12. Three-Tier Architecture: Separate data (Score.sol) from logic (Manager.sol).
13. Abstract Reusable Logic: Centralize modifiers in a base contract.
14. Modular Design: Single-responsibility contracts (e.g., split Roles by entity).
15. Use Audited Libraries: OpenZeppelin for battle-tested code.
16. Reserve Fields: Add spacer variables for future upgrades.

FAQs

Q: How to reuse data during contract upgrades?

A: Adopt a three-layer pattern—update only logic contracts while retaining data contracts.

Q: Can smart contracts handle percentages safely?

A: Multiply by 1000 pre-chain (e.g., 25.5% → 25500), then divide post-chain.

Q: Are fuzzy queries possible on-chain?

A: No. Export data to off-chain systems for analytics.

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