Create Solidity Interface

Now, we'll create a Solidity interface for our Stateful Precompile.

StringStore Solidity Interface

To start, let's look at the interface of the StringStore precompile:

// SPDX-License-Identifier: MIT
 
pragma solidity >=0.8.0;
 
interface IStringStore {
    function getString() external view returns (string memory value);
    function setString(string memory value) external;
}

As seen above, we have the following two functions defined:

1. getString: retreives the string from the stateful precompile
2. setString: sets a string in the stateful precompile

Create Solidity Interface for Counter

Create an interface for the counter in the same directory called ICounter.sol. Your interface should have the following three functions declared:

1. getCounter: returns the counter value from the stateful precompile
2. incrementCounter: when called, this function increments the current counter
3. setCounter: takes in a value, and sets it as the counter of the stateful precompile

For any argument/return value, make sure it is named as value.

Generate the ABI

Now that we have an interface of our precompile, let's create an ABI of our Solidity interface. Open the terminal (control + `), change to the /contracts directory, and run the command to compile the solidity interface to ABI:

# Move to contracts directory
cd contracts
 
# Compile ICounter.sol to ABI
npx solc@latest --abi ./contracts/interfaces/ICounter.sol -o ./abis --base-path . --include-path ./node_modules
 
# Rename 
mv ./abis/contracts_interfaces_ICounter_sol_ICounter.abi ./abis/ICounter.abi