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ethereumweb3js

Ethereum web3js method call fail

I have a simple solidity smart contract with method like:

function foo(uint a) public {
    b =  bytes32(1);
        emit Event(a, b);
        emit Event2(a, b);
    }

(full code is here: https://remix.ethereum.org/#optimize=false&version=soljson-v0.4.25+commit.59dbf8f1.js)

and invoke it using web3.js code :

contract = testContract.at('xxxAddress')   

// contract.foo(6); // Failed, Why?

//Success
contract.foo.sendTransaction(6, {from: eth.accounts[1]},function(error, result) {
            console.log("Got err:", error, ", result: ", result) 
    }
);

but, why straightforward contract.foo(6) failed? Can any expert explain it?

Solution

  • The call to a function that modifies the blockchain needs to send as a transaction since it requires gas to run. This is why you need to send a transaction and not just call the function. You can find more about it here.