state_call - JSON-RPC Method

Description

Performs a runtime API call at a given block. This JSON-RPC method allows you to execute runtime functions to query information without submitting transactions. Common uses include querying account nonces, validating transactions, and accessing runtime-specific data.

Parameters

Parameter	Type	Required	Description
method	string	Yes	Name of the runtime API method to call
data	string	Yes	Hex-encoded parameters for the method
blockHash	string	No	Block hash to call at. If omitted, uses the latest block

Returns

Field	Type	Description
result	string	Hex-encoded result from the runtime API call

Request Example

{
  "jsonrpc": "2.0",
  "method": "state_call",
  "params": [
    "AccountNonceApi_account_nonce",
    "0xd43593c715fdd31c61141abd04a99fd6822c8558854ccde39a5684e7a56da27d"
  ],
  "id": 1
}

Response Example

{
  "jsonrpc": "2.0",
  "result": "0x0000000000000000",
  "id": 1
}

Common Runtime API Methods

Method	Description	Parameters
AccountNonceApi_account_nonce	Get account nonce	Account address
TransactionPaymentApi_query_info	Query transaction fee	Encoded extrinsic
TransactionPaymentApi_query_fee_details	Get detailed fee breakdown	Encoded extrinsic
BlockBuilder_apply_extrinsic	Validate extrinsic	Encoded extrinsic
Core_version	Get runtime version	None
Metadata_metadata	Get runtime metadata	None

Code Examples

JavaScript

const stateCall = async (method, data, blockHash = null) => {
  const params = blockHash ? [method, data, blockHash] : [method, data];
  
  const response = await fetch('https://api-polkadot.n.dwellir.com', {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer YOUR_API_KEY',
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      jsonrpc: '2.0',
      method: 'state_call',
      params: params,
      id: 1
    })
  });
  
  const result = await response.json();
  return result.result;
};

// Get account nonce
const getNonce = async (address) => {
  const data = '0x' + Buffer.from(address.slice(2), 'hex').toString('hex');
  const result = await stateCall('AccountNonceApi_account_nonce', data);
  return parseInt(result, 16);
};

// Query transaction fees
const queryFees = async (encodedTx) => {
  const result = await stateCall(
    'TransactionPaymentApi_query_info',
    encodedTx
  );
  // Decode the result based on the expected format
  return result;
};

Python

import requests
import json
from substrateinterface import SubstrateInterface

def state_call(method, data, block_hash=None):
    url = "https://api-polkadot.n.dwellir.com"
    headers = {
        "Authorization": "Bearer YOUR_API_KEY",
        "Content-Type": "application/json"
    }
    
    params = [method, data]
    if block_hash:
        params.append(block_hash)
    
    payload = {
        "jsonrpc": "2.0",
        "method": "state_call",
        "params": params,
        "id": 1
    }
    
    response = requests.post(url, headers=headers, data=json.dumps(payload))
    return response.json()["result"]

# Example: Get account nonce
def get_account_nonce(address):
    # Encode address properly
    substrate = SubstrateInterface(url="https://api-polkadot.n.dwellir.com")
    account_id = substrate.ss58_decode(address)
    data = "0x" + account_id
    
    result = state_call("AccountNonceApi_account_nonce", data)
    return int(result, 16)

# Example: Query runtime version
def get_runtime_version():
    result = state_call("Core_version", "0x")
    # Decode SCALE-encoded version info
    return result

TypeScript (@polkadot/api)

import { ApiPromise, WsProvider } from '@polkadot/api';

async function makeRuntimeCall() {
  const provider = new WsProvider('wss://api-polkadot.n.dwellir.com');
  const api = await ApiPromise.create({ provider });
  
  // Using high-level API (preferred)
  const nonce = await api.call.accountNonceApi.accountNonce(
    'ADDRESS_HERE'
  );
  console.log('Account nonce:', nonce.toNumber());
  
  // Using low-level state_call
  const address = api.createType('AccountId', 'ADDRESS_HERE');
  const result = await api.rpc.state.call(
    'AccountNonceApi_account_nonce',
    address.toHex()
  );
  console.log('Raw result:', result.toHex());
  
  // Query transaction payment
  const tx = api.tx.balances.transfer('RECIPIENT', 1000000000000);
  const paymentInfo = await api.call.transactionPaymentApi.queryInfo(
    tx.toHex(),
    tx.length
  );
  console.log('Fee:', paymentInfo.toHuman());
  
  await api.disconnect();
}

Fee Calculation Example

// Calculate fees before submission
async function calculateFees(api, transaction) {
  const info = await api.call.transactionPaymentApi.queryInfo(
    transaction.toHex(),
    transaction.encodedLength
  );
  
  return {
    weight: info.weight.toNumber(),
    class: info.class.toString(),
    partialFee: info.partialFee.toNumber()
  };
}

Use Cases

1. Fee Estimation: Calculate transaction costs before submission
2. Nonce Management: Get current account nonce for transaction construction
3. Validation: Verify transactions will succeed before submission
4. Runtime Queries: Access runtime-specific information
5. Custom Logic: Execute specialized runtime functions

Notes

• Results are SCALE-encoded and need proper decoding
• Method names are case-sensitive
• Some methods require specific runtime APIs to be available
• Use high-level APIs when available for automatic encoding/decoding
• Results may vary based on the block state

Related Methods

• state_getMetadata - Get runtime metadata
• state_getRuntimeVersion - Get runtime version
• state_getStorage - Query storage directly
• author_submitExtrinsic - Submit transactions