Step 7: Constructor Arguments

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Constructor Model

If your contract has a parameterized constructor, Neo handles it through the _deploy(data, update) entry point. The compiler automatically generates this entry point.

Example Contract

Example contract with a constructor:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.34;

contract Counter {
    uint256 private count;

    constructor(uint256 initialCount) {
        count = initialCount;
    }

    function get() public view returns (uint256) {
        return count;
    }
}

Compile

Compile:

./target/release/neo-solc Counter.sol -I devpack -O2 -o build/Counter

Deploy with Arguments

Deploy with constructor arguments via Neo-Express:

$NEOXP contract deploy -i chain.neo-express -d '[100]' build/Counter.nef node1

The -d '[100]' flag passes a JSON array as the data parameter to _deploy. The compiler's deploy stub deserializes this array and passes the values to your Solidity constructor.

Manifest Permissions

Contracts with parameterized constructors require StdLib.jsonDeserialize and StdLib.deserialize permissions in the manifest. The compiler adds these automatically.