EVM Provider

The Tomo Telegram SDK implements the Ethereum Provider, allowing seamless integration with existing Ethereum-compatible DApps.

To use the EVM provider in your application, you need first to install the sdk and get the wallet provider:

// get provider 
const ethereum = window.ethereum;

Below are methods that developers can use with our EVM provider.

Connect with the Wallet​

Before using the provider, the user needs to log in to the wallet through the modal by following the method:

// connect wallet
await ethereum?.connectWallet();

The isConnected method returns a boolean value indicating whether the wallet is connected or not.

  ethereum.isConnected(): boolean

Query Methods​

The request method is used to make an RPC request to the connected wallet. For detailed information on JSON-RPC methods, refer to:

We provide some frequently use methods as below:​

Get accounts​ address

Connects to the wallet and returns the address of the connected wallet. In Tomo, the return value is the first address in the response.

const accounts = await ethereum.request({ method: 'eth_requestAccounts' });

Get chain ID

Returns the chain ID of the connected wallet.

const chainId = await ethereum.request({ method: 'eth_chainId' });

Get balance

Returns the balance of eth in wei of hex format.

// eth_getBalance
const hexAmount= await window.ethereum.request({
  method: 'eth_getBalance',
  params: [addr, 'latest'],
});


const weiAmount = BigInt(hexAmount);

// const ethAmount = weiAmount / BigInt(10 ** 18);
const ethDecimal = Number(weiAmount) / 1e18;
const weiString = weiAmount.toString();

Sign Message

The Tomo Telegram SDK supports signing messages through the request method under Metamask standard:

  • personal_sign

  • eth_signTypedData

  • eth_signTypedData_v3

  • eth_signTypedData_v4

The return value is the signature data. For detailed usage, refer to:

Example of personal_sign:

const accounts = await ethereum.request({ method: 'eth_accounts' });
const chainId =  await ethereum.request({ method: 'eth_chainId' });

const signature = await ethereum.request({
  method: 'personal_sign',
  params: ['Hello, Tomo!', accounts[0]]
});

Example of eth_signTypedData_v4:


const  accounts = await ethereum.request({ method: 'eth_accounts' });
const  chainId  =  await ethereum.request({ method: 'eth_chainId' });

const  msgParams = {
    "domain": {
        "chainId": chainId,
        "name": "Ether Mail",
        "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC",
        "version": "1"
    },
    "message": {
        "contents": "Hello, Bob!",
        "from": {
            "name": "Cow",
            "wallets": [
                "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826",
                "0xDeaDbeefdEAdbeefdEadbEEFdeadbeEFdEaDbeeF"
            ]
        },
        "to": [
            {
                "name": "Bob",
                "wallets": [
                    "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB",
                    "0xB0BdaBea57B0BDABeA57b0bdABEA57b0BDabEa57",
                    "0xB0B0b0b0b0b0B000000000000000000000000000"
                ]
            }
        ],
        "attachment": "0x"
    },
    ...
}

const signatureV4 = await ethereum.request({
  method: 'eth_signTypedData_v4',
  params: [
    accounts[0], 
    JSON.stringify(msgParams)
  ]
});

Sign Transaction

eth_signTransaction method will return a response with a signed transaction. For users to verify the transaction contents, we only support passing parameters to the SDK and letting the user decide whether to sign the created transaction or not.

Transfer transaction

// simple transfer transaction
const response1 = await ethereum.request({
      method: 'eth_signTransaction',
      params: [
        {
          from: addr,
          to: toAddr1,
          value: hexString,
          gas: hexString,
          gasPrice: hexString,
          nonce: hexString,
          chainId: hexString,
        },
      ],
    });

Contract call transaction


    
// transaction call contract 
const response2 = await ethereum.request({
      method: 'eth_signETHTransaction',
      params: [
        {
          from: addr,
          to: contractAddr,
          value: int,
          chainId: hexString,
          data: hexData,
        },
      ],
    });

Send Transaction

Currently, Tomo SDK does not connect to RPC nodes for EVM chains. Therefore, developers must send the transaction directly with a standard EVM library.

const provider = new Web3.providers.HttpProvider(
  `url for rpc nodes`
);
const web3 = new Web3(provider);
try {
  const res = await web3.eth.sendSignedTransaction(serializedTx);
  console.log('result:', res);
} catch (error) {
  console.log(error);
  return;
}

Switch Ethereum Chain​

Switches the connected wallet to the specified chain ID.

try {
  await ethereum.request({
    method: 'wallet_switchEthereumChain',
    params: [{ chainId: '0xf00' }],
  });
} catch (switchError) {
  // error handle
}

Event Listeners​

The SDK emits events for account and network changes.

accountsChanged​

ethereum.on('accountsChanged', (accounts) => {//error handle };

chainChanged​

ethereum.on('chainChanged', (chainId) => {//error handle });

To remove listeners:

ethereum.removeListener('accountsChanged', handleAccountsChanged);
// or remove all listeners
ethereum.removeAllListeners();
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