Data Loaders

Data Loaders are mechanisms for retrieving the necessary ABI and Contract Metadata for transaction decoding. They are responsible for:

Resolving ABIs and Contract Metadata using specified strategies and third-party APIs
Automatically batching requests when processing logs and traces in parallel
Caching request results in the Data Store

Loop Decoder implements optimizations to minimize API requests to third-party services. For example, when a contract’s ABI is resolved via Etherscan, it is cached in the store. If the ABI is requested again, the store provides the cached version, avoiding redundant API calls.

ABI Strategies

ABI strategies will receive the contract address, and event or function signature as input and would return the ABI as a stringified JSON. Loop Decoder provides some strategies out of the box:

EtherscanStrategyResolver - resolves the ABI from Etherscan, requires an API key to work properly
EtherscanV2StrategyResolver - resolves the ABI from Etherscan v2, requires an API key to work properly
SourcifyStrategyResolver - resolves the ABI from Sourcify
FourByteStrategyResolver - resolves the ABI from 4byte.directory
OpenchainStrategyResolver - resolves the ABI from Openchain
BlockscoutStrategyResolver - resolves the ABI from Blockscout

You can create your strategy by implementing the GetContractABIStrategy Effect RequestResolver.

Contract Metadata Strategies

Contract metadata is a collection of information about a contract, such as the contract’s name, symbol, and decimals.

Loop Decoder provides some strategies out of the box:

ERC20RPCStrategyResolver - resolves the contract metadata of an ERC20 token from the RPC
NFTRPCStrategyResolver - resolves the contract metadata of an NFT token (ERC721, ERC1155) from the RPC
ProxyRPCStrategyResolver - resolves the contract metadata of a Gnosis Safe proxy contract from the RPC

Code Examples

const AbiStoreLive = SqlAbiStore.make({
  default: [
    EtherscanV2StrategyResolver({
      apikey: process.env.ETHERSCAN_API_KEY,
    }),
    FourByteStrategyResolver(),
  ],
  //...
})

const abiStore: VanillaAbiStore = {
  strategies: [
    EtherscanStrategyResolver({
      apikey: process.env.ETHERSCAN_API_KEY || '',
    }),
    FourByteStrategyResolver(),
  ],
  //...
}

Initializing Contract Metadata Strategies

Effect API
Vanilla JS API

const MetaStoreLive = Layer.unwrapEffect(
  Effect.gen(function* () {
    const service = yield* PublicClient

    return SqlContractMetaStore.make({
      default: [ERC20RPCStrategyResolver(service), NFTRPCStrategyResolver(service)],
    })

}),
)

const contractMetaStore: VanillaContractMetaStore = {
  strategies: [ERC20RPCStrategyResolver, NFTRPCStrategyResolver],
  //...
}