README.md

Allow and Transfer on ERC20

In this example we simulate a common transaction sequence in which a user first approves another address (the spender), by calling approve method, to spend their tokens, which is followed by the spender calling transferFrom method on the contract to transfer the actual tokens.

    import { Interface } from 'ethers';
    import { myTokenAbi } from './myTokenAbi'; // ABI of the ERC20 token contract

    ...

    const myTokenAddress = '0x912043e00a14a6b79f5e500c825b1439e812d7ce';
    const fromWalletAddress = '0x8d1d4e2b8b9b1b4b9e0d0d6d7c7c4e4e8d9d00e0';
    const toWalletAddress = '0xDBcB6Db1FFEaA10cd157F985a8543261250eFA46';

    const myTokenAbiInterface = new Interface(myTokenAbi);

    const simulations = await tenderly.simulator.simulateBundle({
      transactions: [
        {
          from: fromWalletAddress,
          to: myTokenAddress,
          gas: 0,
          gas_price: '0',
          value: 0,
          input: myTokenAbiInterface.encodeFunctionData('approve', [toWalletAddress, 1234567890]),
        },
        {
          from: toWalletAddress,
          to: myTokenAddress,
          gas: 0,
          gas_price: '0',
          value: 0,
          input: myTokenAbiInterface.encodeFunctionData('transferFrom', [
            fromWalletAddress,
            toWalletAddress,
            1234567890,
          ]),
        },
      ],
      blockNumber: 3262454,
      overrides: {
        [myTokenAddress]: {
          state: {
            [`_balances[${fromWalletAddress}]`]: '1234567891',
          },
        },
      },
    });

Notice the overrides argument in for this transaction bundle:

overrides: {
        [myTokenAddress]: {
          state: {
            [`_balances[${fromWalletAddress}]`]: '1234567891',
          },
        },
      },

This is used to override the state of the contract, in this case the balance of the sender. This is useful when you want to simulate a transaction bundle that is not possible in the current state of the contract.