I want to write a simple function to call the method on contract and get the running result,
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);
}
// 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"
console.log(r);
})
.catch((e) => {
console.error(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?
I think I got the solution from this Ethereum.StackExchange post:
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.
Source: Taylor Gerring, Apr 23, 2016 at 7:47 AM
N.B. - the answer has been updated at the original location to reflect changes in Solidity.