OTP-002: Contract ABI

ABI defines how to communicate with smart contracts. It contains information about the contract’s receivers, data structures, etc.

Motivation

ABI is an essential tool that allows developers to generate handy bindings, UIs, etc. One of the best consumer usages would be using a DAO and being able to confirm what exactly it is trying to do before signing a transaction.

Guide

This OTP is based on types that are defined in TLB+ and it is advised to know them before reading this OTP.

Specification

ABI is a JSON file:

{
  "name": "MyContract",
  "types": [
    {
      "name": "MyRequest",
      "header": 12315123,
      "fields": [
        {
          "name": "queryId",
          "type": {
            "kind": "simple",
            "type": "int",
            "optional": false,
            "format": "uint256"
          }
        }
      ]
    }
  ],
  "receivers": [
    { "type": "binary", "kind": "internal", "name": "MyRequest" },
    { "type": "binary", "kind": "internal" },
    { "type": "comment", "kind": "internal", "comment": "Vote!" },
    { "type": "comment", "kind": "internal" },
    { "type": "empty", "kind": "internal" }
  ],
  "getters": [
    { "name": "getOwner", "type": "address", "args": [] },
    {
      "name": "getBalance",
      "type": "coins",
      "args": [
        {
          "name": "invested",
          "type": {
            "kind": "simple",
            "type": "uint",
            "format": "coins"
          }
        }
      ]
    }
  ],
  "errors": {
    "123": "Error description",
    "124": "Division by zero"
  }
}

Drawbacks

• Binary and compact representation of ABI could be better, but it is not critical for now.

Prior art

• OTP-001, that is complimentary to this OTP.