🤖
LNS Documentation
  • Introduction
  • Terminology
  • Frequently Asked Questions
  • Tokenomics
  • LNS Deployments
  • Registrar Frequently Asked Questions
  • Deploying LNS on a Private Chain
  • DNS Registrar guide
  • Bug Bounty Program
  • ENS Improvement Proposals
    • ENSIP-1: ENS
    • ENSIP-2: Initial Hash Registrar
    • ENSIP-3: Reverse Resolution
    • ENSIP-4: Support for contract ABIs
    • ENSIP-5: Text Records
    • ENSIP-6: DNS-in-ENS
    • ENSIP-7: Contenthash field
    • ENSIP-8: Interface Discovery
    • ENSIP-9: Multichain Address Resolution
    • ENSIP-10: Wildcard Resolution
    • ENSIP-11: EVM compatible Chain Address Resolution
    • ENSIP-12: Avatar Text Records
  • Dapp Developer Guide
    • LNS Enabling your DApp
    • LNS Libraries
    • Working with LNS
    • Resolving Names
    • Managing Names
    • Registering & Renewing Names
    • LNS Front-End Design Guidelines
    • LNS as NFT
  • Contract API Reference
    • Name Processing
    • Registry
    • ReverseRegistrar
    • PublicResolver
    • .bch Permanent Registrar
      • Registrar
      • Controller
    • DNS Registrar
  • Contract Developer Guide
    • Resolving Names On-chain
    • Writing a Resolver
    • Writing a Registrar
    • LNS Support Chat
Powered by GitBook
On this page
Edit on GitHub
  1. Contract Developer Guide

Writing a Resolver

PreviousResolving Names On-chainNextWriting a Registrar

Last updated 3 years ago

Resolvers are specified in . A resolver must implement the following method:

function supportsInterface(bytes4 interfaceID) constant returns (bool);

supportsInterface is defined in , and allows callers to determine if a resolver supports a particular record type. Record types are specified as a set of one or more methods that a resolver must implement together. Currently defined record types include:

Record type
Function(s)
Interface ID
Defined in

smartBCH address

addr

0x3b3b57de

LNS Name

name

0x691f3431

ABI specification

ABI

0x2203ab56

Public key

pubkey

0xc8690233

Text records

text

0x59d1d43c

Content hash

contenthash

0xbc1c58d1

supportsInterface must also return true for the interfaceID value 0x01ffc9a7, which is the interface ID of supportsInterface itself.

Additionally, the content interface was used as a defacto standard for Swarm hashes, and has an interface ID of 0xd8389dc5. New implementations should use contenthash instead.

Example Resolver

A simple resolver that supports only the addr type might look something like this:

contract SimpleResolver {
    function supportsInterface(bytes4 interfaceID) constant returns (bool) {
        return interfaceID == 0x3b3b57de;
    }

    function addr(bytes32 nodeID) constant returns (address) {
        return address(this);
    }
}

This trivial resolver always returns its own address as answer to all queries. Practical resolvers may use any mechanism they wish to determine what results to return, though they should be constant, and should minimise gas usage wherever possible.

EIP137
EIP165
EIP137
EIP181
EIP205
EIP619
EIP634