8.2.5 Interchain Services based on Neo Testnet

Application Contract Development Guide

The development of Neo application contract is based on its own business scenario. The main implementation includes two parts: if the source chain initiates a cross-chain transaction, its application contract needs to get outbound to access the target chain; if the target chain receives a cross-chain transaction, its application contract needs to get inbound. Neo has a chain ID of 4, which is registered on Poly Enterprise, and its configuration is applicable to the BSN production environment.

Below is an example of a source chain initiating a cross-chain transaction call:

{
    /// <summary>
    /// This method is used to make cross-chain calls to other target chains (this method is self-defining)
    /// </summary>
    /// <param name="toChainId">The chain ID of the target chain in the Poly network</param>
    /// <param name="msg">The cross-chain information that the target chain needs to pass to apply the contract</param>
    /// <returns></returns>
    [DisplayName("say")]
    public static bool Say(BigInteger toChainId, string method ,byte[] msg)
    {
        // Get the application contract on the target chain
        var toProxyHash = HelloPoly.GetProxyHash(toChainId);
        // Get the CCMC contract address
        var ccmcScriptHash = HelloPoly.GetProxyHash(neoChainID);
        // Call across the chains

        bool success = (bool)((DynCall)ccmcScriptHash.ToDelegate())("CrossChain", new object[] { toChainId, toProxyHash, method, msg });

        HelloPoly.Notify(success, "[HelloPoly]-Say: Failed to call CCMC.");
        // Event notification
        HelloPoly.SayEvent(toChainId, toProxyHash);
        return true;
    }
}

Below is an example of a target chain call when receiving a cross-chain transaction:

{
    /// <summary>
    /// This method is used to make cross-chain calls to other target chains (this method is self-defining)
    /// </summary>
    /// <param name="fromChainId">The chain ID of the source chain in a Poly network</param>
    /// <param name="toChainId">The chain ID of the target chain in the Poly network</param>
    /// <param name="msg">Receive a cross-chain message sent by the source chain</param>
    /// <param name="callingScriptHash">Callback script hash</param>
    /// <returns></returns>
    [DisplayName("hear")]
    public static bool Hear(byte[] inputBytes, byte[] fromProxyContract, BigInteger fromChainId, byte[] callingScriptHash)
        //commit into ledger
        Storage.Put(fromProxyContract, inputBytes);
        // Event notification
        HearEvent(fromChainId, fromProxyContract, inputBytes);
        return true;
    }

Demo Contract Example

GitHub: https://github.com/BSNDA/ICH/tree/main/sample/polychain/neo-contract