Eval

Each AO process includes an onboard Eval handler that evaluates any new code it receives. This handler determines the appropriate action for the code and verifies that the message originates from the process owner.

The Eval handler can also be manually triggered to evaluate the Data field from an incoming message. When you use the .load function to load a file into a process, it relies on the Eval handler to evaluate the file’s content under the hood.

Sending an Eval Message in NodeJS

import { readFileSync } from "node:fs";
import { message, createDataItemSigner } from "@permaweb/aoconnect";

const wallet = JSON.parse(
  readFileSync("/path/to/arweave/wallet.json").toString(),
);

await message({
  // The arweave TxID of the process, this will become the "target".
  process: "process-ID", // Replace with the actual process ID

  // Tagging the Eval Action so the receiving process evaluates and adds the new Handler from the Data field.
  tags: [
    { name: "Action", value: "Eval" },
    {
      name: "Data",
      value: 'Handlers.add("ping", Handlers.utils.reply("pong"))',
    },
  ],

  // A signer function used to build the message "signature"
  signer: createDataItemSigner(wallet),
})
  .then(console.log)
  .catch(console.error);

Sending an Eval Message in a Browser

import { message, createDataItemSigner } from "@permaweb/aoconnect";

await message({
  // The arweave TxID of the process, this will become the "target".
  process: "process-ID", // Replace with the actual process ID

  // Tagging the Eval Action so the receiving process evaluates and adds the new Handler from the Data field.
  tags: [
    { name: "Action", value: "Eval" },
    {
      name: "Data",
      value: 'Handlers.add("ping", Handlers.utils.reply("pong"))',
    },
  ],

  // A signer function used to build the message "signature"
  signer: createDataItemSigner(globalThis.arweaveWallet),
})
  .then(console.log)
  .catch(console.error);