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Getting a Contract ABI

The ABI (Application Binary Interface) defines the methods and events of a smart contract, serving as a blueprint for interacting with it. On OP_NET, creating a JSON ABI is straightforward and allows you to define the structure of your contract's functions, properties, and events.

Creating a Contract JSON ABI​

To create a contract ABI, you need to define the functions and events using the appropriate types from the OP_NET library. Below is a breakdown of how to create a JSON ABI for an OP_20 token contract.

Example: OP_20 ABI Definition​

Dependencies​

Ensure you import the necessary types and helpers for defining your ABI:

import { ABIDataTypes } from "@btc-vision/transaction";
import { BitcoinAbiTypes, BitcoinInterfaceAbi, OP_NET_ABI } from "opnet";

Event Definitions​

Define the contract's events. For OP_20, these include events such as Mint, Transfer, and Approve:

export const OP20Events: BitcoinInterfaceAbi = [
  {
    name: "Mint",
    values: [
      { name: "to", type: ABIDataTypes.ADDRESS },
      { name: "amount", type: ABIDataTypes.UINT256 },
    ],
    type: BitcoinAbiTypes.Event,
  },
  {
    name: "Transfer",
    values: [
      { name: "from", type: ABIDataTypes.ADDRESS },
      { name: "to", type: ABIDataTypes.ADDRESS },
      { name: "amount", type: ABIDataTypes.UINT256 },
    ],
    type: BitcoinAbiTypes.Event,
  },
  {
    name: "Approve",
    values: [
      { name: "owner", type: ABIDataTypes.ADDRESS },
      { name: "spender", type: ABIDataTypes.ADDRESS },
      { name: "value", type: ABIDataTypes.UINT256 },
    ],
    type: BitcoinAbiTypes.Event,
  },
];

Function Definitions​

Functions are the primary way to interact with a contract. Each function includes:

  • Inputs: Parameters passed to the function.
  • Outputs: Return values from the function.

For example, defining the balanceOf function:

export const OP_20_ABI: BitcoinInterfaceAbi = [
  {
    name: "balanceOf",
    inputs: [{ name: "account", type: ABIDataTypes.ADDRESS }],
    outputs: [{ name: "balance", type: ABIDataTypes.UINT256 }],
    type: BitcoinAbiTypes.Function,
  },
];

Combining Events and Functions​

Combine events, functions, and any additional properties to create the complete ABI:

export const OP_20_ABI: BitcoinInterfaceAbi = [
  // Functions
  {
    name: "transfer",
    inputs: [
      { name: "recipient", type: ABIDataTypes.ADDRESS },
      { name: "amount", type: ABIDataTypes.UINT256 },
    ],
    outputs: [{ name: "success", type: ABIDataTypes.BOOL }],
    type: BitcoinAbiTypes.Function,
  },
  {
    name: "approve",
    inputs: [
      { name: "spender", type: ABIDataTypes.ADDRESS },
      { name: "amount", type: ABIDataTypes.UINT256 },
    ],
    outputs: [{ name: "success", type: ABIDataTypes.BOOL }],
    type: BitcoinAbiTypes.Function,
  },
  // Properties
  {
    name: "totalSupply",
    outputs: [{ name: "totalSupply", type: ABIDataTypes.UINT256 }],
    type: BitcoinAbiTypes.Function,
  },
  // Events
  ...OP20Events,
  // OP_NET Specific
  ...OP_NET_ABI,
];
ABI Components Overview
  • Functions
    Define contract methods with inputs and outputs, specifying their data types (ABIDataTypes).
  • Events
    Include event definitions for tracking on-chain interactions.
  • Properties
    Add constant values or properties that can be queried from the contract.
  • OP_NET-Specific Extensions Extend with OP_NET-specific functionality by importing OP_NET_ABI.

Best Practices​

  • Use ABIDataTypes for parameter and return types.
  • Modularize event and function definitions for easy maintenance.
  • Test the ABI against a deployed contract to ensure correctness.

What’s Next?​

Now that you understand the basics, explore the following topics to dive deeper into contract interactions:

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