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<Tabs queryString="typegen">
<Tab value="evm" label="squid-evm-typegen">
In order to make on-chain calls, one must set up a JSON-RPC endpoint using setRpcEndpoint(). We recommend using a private endpoint from e.g. BlastAPI or the SQD Cloud’s RPC addon, and set it via an environment variable: 
//...
  .setRpcEndpoint(process.env.RPC_ETH_HTTP)
//...
You can define the RPC_ETH_HTTP in three ways:
  • for local runs, simply update the local .env file;
  • for squids deployed to Cloud define it as a secret on your Cloud account;
  • if you are using the RPC addon, leave it to the Cloud to define it for you.

​
Contract class

The EVM contract state is accessed using the Contract class generated by squid-evm-typegen. It takes a handler context and a contract address as constructor arguments. The state is always accessed at the context block height unless explicitly defined in the constructor. For example, assume that we index an ERC721 contract. Typescript ABI module generated with squid-evm-typegen will contain the following class: 
export class Contract extends ContractBase {
  //...
  balanceOf(owner: string): Promise<ethers.BigNumber> {
    return this.call('balanceOf', [owner])
  }
  //...
}
Now suppose we want to query our contract from the batch handler. To create a Contract pass the context object and the current Block to its constructor, then query the contract state at that block: 
// ...
const CONTRACT_ADDRESS = '0xb654611f84a8dc429ba3cb4fda9fad236c505a1a'

processor.run(new TypeormDatabase(), async ctx => {
  for (const block of ctx.blocks) { 
    const contract = new abi.Contract(ctx, block.header, CONTRACT_ADDRESS)
    // query the contract state at the current block
    const uri = await contract.balanceOf('0xd8da6bf26964af9d7eed9e03e53415d37aa96045')
    // ...
  }
})

​
Batch state queries

The MakerDAO Multicall contract was designed to batch multiple state queries into a single contract call. In the context of indexing, it normally significantly improves the indexing speed since JSON RPC calls are typically the bottleneck. Multicall contracts are deployed in many EVM chains, see the contract repo for addresses. You can use any of them with a multicall Typescript module that is generated when running squid-evm-typegen with --multicall option. The module exports a Multicall class with this method: 
tryAggregate<Args extends any[], R>(
  func: Func<Args, {}, R>,
  calls: [address: string, args: Args][],
  paging?: number
): Promise<MulticallResult<R>[]>
The arguments are as follows:
  • func: the contract function to be called
  • calls: an array of tuples [contractAddress: string, args]. Each specified contract will be called with the specified arguments.
  • paging an (optional) argument for the maximal number of calls to be batched into a single JSON PRC request. Note that large page sizes may cause timeouts.
A typical usage is as follows:
src/main.ts
// generated by evm-typegen
import \{ functions \} from './abi/mycontract'
import \{ Multicall \} from './abi/multicall'

const MY_CONTRACT = '0xac5c7493036de60e63eb81c5e9a440b42f47ebf5'
const MULTICALL_CONTRACT = '0x5ba1e12693dc8f9c48aad8770482f4739beed696'

processor.run(new TypeormDatabase(), async (ctx) => {
  for (let c of ctx.blocks) {
    // some logic
  }
  const lastBlock = ctx.blocks[ctx.blocks.length - 1]
  const multicall = new Multicall(
    ctx,
    lastBlock,
    MULTICALL_CONTRACT
  )
  // call MY_CONTRACT.myContractMethod('foo') and MY_CONTRACT.myContractMethod('bar')
  const args = ['foo', 'bar']
  const results = await multicall.tryAggregate(
    functions.myContractMethod,
    args.map(a => [MY_CONTRACT, a]) as [string, any[]],
    100
  )

  results.forEach((res, i) => {
    if (res.success) {
      ctx.log.info(`Result for argument $\{args[i]\} is $\{res.value\}`)
    }
  })
})

</Tab>
<Tab value="substrate" label="squid-substrate-typegen">
It is sometimes impossible to extract the required data with only event and call data without querying the runtime state. The context exposes a lightweight gRPC client to the chain node accessible via ctx._chain. It exposes low-level methods for accessing the storage. However, the recommended way to query the storage is with type-safe wrappers generated with squid-substrate-typegen. Substrate typegen tool exposes storage access wrappers at src/types/storage.ts. The wrappers follow the general naming pattern used by Substrate typegen: 
storage.$\{palletName\}.$\{storageName\}
with all identifiers lowerCamelCased. Each wrapper exposes a generated get() query method and, if available, methods for multi-key queries, listing keys, key-value pairs and retrieving the default value. Note that the generated getters always query historical blockchain state at the height derived from their block argument. Here is an example of one such wrapper:
src/types/balances/storage.ts
import \{sts, Block, Bytes, Option, Result, StorageType\} from '../support'
import * as v1050 from '../v1050'
import * as v9420 from '../v9420'

export const account = {
  v1050: new StorageType('Balances.Account', 'Default', [v1050.AccountId], v1050.AccountData) as AccountV1050,
  v9420: new StorageType('Balances.Account', 'Default', [v9420.AccountId32], v9420.AccountData) as AccountV9420,
}

export interface AccountV1050  {
  getDefault(block: Block): v1050.AccountData
  get(block: Block, key: v1050.AccountId): Promise<v1050.AccountData | undefined>
  getMany(block: Block, keys: v1050.AccountId[]): Promise<v1050.AccountData | undefined[]>
}

export interface AccountV9420  {
  getDefault(block: Block): v9420.AccountData
  get(block: Block, key: v9420.AccountId32): Promise<v9420.AccountData | undefined>
  getMany(block: Block, keys: v9420.AccountId32[]): Promise<v9420.AccountData | undefined[]>
  getKeys(block: Block): Promise<v9420.AccountId32[]>
  getKeys(block: Block, key: v9420.AccountId32): Promise<v9420.AccountId32[]>
  getKeysPaged(pageSize: number, block: Block): AsyncIterable<v9420.AccountId32[]>
  getKeysPaged(pageSize: number, block: Block, key: v9420.AccountId32): AsyncIterable<v9420.AccountId32[]>
  getPairs(block: Block): Promise<[k: v9420.AccountId32, v: v9420.AccountData | undefined][]>
  getPairs(block: Block, key: v9420.AccountId32): Promise<[k: v9420.AccountId32, v: v9420.AccountData | undefined][]>
  getPairsPaged(pageSize: number, block: Block): AsyncIterable<[k: v9420.AccountId32, v: v9420.AccountData | undefined][]>
  getPairsPaged(pageSize: number, block: Block, key: v9420.AccountId32): AsyncIterable<[k: v9420.AccountId32, v: v9420.AccountData | undefined][]>
}
The generated access interface provides methods for accessing:
  • the default storage value with getDefault(block)
  • a single storage value with get(block, key)
  • multiple values in a batch call with getMany(block, keys[])
  • all storage keys with getKeys(block)
  • all keys with a given prefix with getKeys(block, keyPrefix) (only if the storage keys are decodable)
  • paginated keys via getKeysPaged(pageSize, block) and getKeysPaged(pageSize, block, keyPrefix)
  • key-value pairs via getPairs(block) and getPairs(block, keyPrefix)
  • paginated key-value pairs via getPairsPaged(pageSize, block) and getPairsPaged(pageSize, block, keyPrefix)

​
Example

src/main.ts
import \{storage\} from './types'

processor.run(new TypeormDatabase(), async ctx => {
  let aliceAddress = ss58.decode('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY').bytes
  for (const blockData of ctx.blocks) {
    if (storage.balances.account.v1050.is(blockData.header)) {
      let aliceBalance = (await storage.balances.account.v1050.get(blockData.header, aliceAddress))?.free
      ctx.log.info(`Alice free account balance at block $\{blockData.header.height\}: $\{aliceBalance\}`)
    }
  }
})

</Tab>
<Tab value="ink" label="squid-ink-typegen">
The generated Contract class provides facades for all state calls that don’t mutate the contract state. The info about the state mutability is taken from the contract metadata. 
// Generated code:
export class Contract {
    // optional blockHash indicates the block at which the state is queried
    constructor(private ctx: ChainContext, private address: string, private blockHash?: string) \{ \}

    total_supply(): Promise<Balance> {
        return this.stateCall('0xdb6375a8', [])
    }

    balance_of(owner: Uint8Array): Promise<bigint> {
        return this.stateCall('0x6568382f', [owner])
    }
}

​
Example

processor.run(new TypeormDatabase(), async ctx => {
  for (let block of ctx.blocks) {
    for (let event of block.events) {
       // query the balance at the current block
       const contract = new Contract(ctx, CONTRACT_ADDRESS, block.header.hash)
       let aliceAddress = ss58.decode('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY').bytes
       let aliceBalance = await contract.balance_of(aliceAddress)
    }
  }
})

</Tab>
</Tabs>