0 votes
1 view
in Blockchain by (12.8k points)

I want to write a simple function to call the method on contract and get the running result,

This is the contract code

function _evaluate(uint8[5] _uploads) internal returns (bytes32 resultId){

    resultId= keccak256(abi.encodePacked(now,  msg.sender));

    addressToid[msg.sender] = resultId;

    idToResult[resultId] = Result(msg.sender, r);


function upload(uint8[5] _inputs) public returns ( bytes32 resultId) {

    return _evaluate(_inputs);


front end js codes

// DEE is the contract name

return this.DEE.deployed()

        .then((instance) => instance.upload(this.inputs,  {from: base.accounts[0]}))

        .then((r) => {

          this.message = "Transaction done"



        .catch((e) => {


          this.message = "Transaction failed"


but in fact, I found r returned is a ** transaction detail**, like,

{tx: "0xa543fff3c3bac2268c0c94a21f6cf62faa8cf667defcd9fd8dcdbcf7669a4e58",

receipt: {…}, logs: Array(0)} logs : [] receipt : {transactionHash: "0xa543fff3c3bac2268c0c94a21f6cf62faa8cf667defcd9fd8dcdbcf7669a4e58", transactionIndex: 0, blockHash: "0x07d691308724c73025de2f346dc0d6bc4eb7e7de9871e29ea2c4d4e8fb8222bb", blockNumber: 20, gasUsed: 56460, …} tx : "0xa543fff3c3bac2268c0c94a21f6cf62faa8cf667defcd9fd8dcdbcf7669a4e58" proto : Object

There is no information about the id which should be returned included.

Did I do something wrong?

1 Answer

0 votes
by (29.8k points)

It is not currently possible to return values from functions which modify the blockchain. To receive a return value, you can mark read-only functions as "constant".
For non-constant functions, the only way to "return" information is by using Solidity Events, which coalesce as LOG opcodes in the Ethereum Virtual Machine.

Welcome to Intellipaat Community. Get your technical queries answered by top developers !