apex-sdk

Smart Contract Orchestration Example

This example demonstrates Apex SDK’s unique capability to orchestrate smart contract calls across both Substrate (ink!) and EVM chains from a single, unified Rust application.

What Makes This Unique

Unlike traditional approaches that require:

• polkadot.js for Substrate interactions
• ethers.js or web3.js for EVM interactions
• JavaScript/TypeScript with runtime type errors
• Complex integration between different SDKs

Apex SDK provides:

• Single Rust codebase for both ecosystems
• Compile-time type safety across all chains
• Unified API with zero context switching
• Native performance without FFI overhead

Use Case: Cross-Chain DeFi Application

The example implements a real-world DeFi workflow:

1. Query balance from Substrate ink! contract (Westend)
2. Execute token swap on EVM DEX (Ethereum Sepolia)
3. Bridge assets from Ethereum to Polkadot
4. Stake wrapped assets in Substrate staking contract
5. Query final position across all chains

All operations use the same SDK with type-safe guarantees!

Running the Example

cd examples/contract-orchestration
cargo run

Key Features Demonstrated

1. Unified Transaction Building

// EVM transaction
let evm_tx = sdk.transaction()
    .from_evm_address(evm_account)
    .to_evm_address(contract)
    .with_data(call_data)
    .build()?;

// Substrate transaction
let substrate_tx = sdk.transaction()
    .from_substrate_account(substrate_account)
    .to_substrate_account(contract)
    .with_data(call_data)
    .build()?;

2. Cross-Chain Operations

// Automatically detects cross-chain transfers
let bridge_tx = sdk.transaction()
    .from_evm_address(evm_account)
    .to_substrate_account(substrate_account)  // Different chain!
    .amount(amount)
    .build()?;

assert!(bridge_tx.is_cross_chain());

3. Type-Safe Contract Calls

Both Substrate and EVM contract calls are:

• Type-checked at compile time
• Encoded automatically
• Validated before submission

Real-World Applications

This pattern enables:

• Cross-chain DEX aggregators that find best prices across Substrate and EVM DEXs
• Unified DeFi dashboards managing positions on multiple chains
• Arbitrage bots executing across Polkadot parachains and Ethereum L2s
• Cross-chain DAOs with governance on one chain, treasury on another
• Multi-chain NFT marketplaces supporting both ecosystems

Learn More

• Apex SDK Documentation
• ink! Smart Contracts
• Substrate Development
• Ethereum Smart Contracts

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