How To Get Ethers.js Response Data

Solidity: function ping() public view returns ( uint ) { return 999999999; } function ping2() public returns ( uint ) { return 999999999; } Javascript Ethers.js: (await co

Solution 1:

(await contract.ping()).toString(); //-> 999999999 ( correct )

ping() is a view function - you can just call it without creating a transaction. So ethers.js doesn't create a transaction and just returns result of the call.

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(await contract.ping2()).toString(); //-> [object Object] ( ?? )

Why does using sendTransaction also return [object Object] ?

ping2() is a regular public function. Which suggests that you need to create a transaction to execute it (even though in this case it doesn't make any state changes so it could be a view function as well).

Ethers.js returns the transaction data instead of the contract function return value, when you're creating a transaction.

There are few ways to read values that the transaction produced using Ethers.js.

• In this case, ping2() doesn't make any state changes and doesn't even read any blockchain data, so it could be a pure function. If it were reading blockchain data, it would be a view function... In both cases, ethers.js returns the result of the function call (not tx).

• Transaction to a setter and calling a getter.

  contract MyContract {
      uint256 value;
  
      function setValue(uint256 _value) public {
          value = _value;
      }
  
      function getValue() public view returns (uint256) {
          returnvalue;
      }
  }
  

  First you create a transaction that executes the setValue() function, and then you make a call to getValue() (without transaction, so it returns the value in your JS).

• Reading event logs that your transaction produced

  eventTransfer(address from, address to, uint256 amount);
  
  function transfer(address _to, uint256 _amount) public {
      emit Transfer(msg.sender, _to, _amount);
  }
  

  You can get the transaction receipt that also contains the event logs (in this case, the Transfer event and its values).