Solidity - Return value of Smart Contract Transaction

Question

Why do Solidity transact functions not return any value?

Here is an easy example. I tested it in remix and web3.

---

pragma solidity ^0.4.25;
contract SimpleStorage {

    uint public storedData;

    constructor(uint initVal) public {
        storedData = initVal;
    }

    function set(uint x) public returns (uint retVal) {
        storedData = x;
        return storedData;
    }

    function get() view public returns (uint retVal) {
        return storedData;
    }

}

I want to call the SET function of this contract and immediately get the recently assigned value returned without calling the GET.

Therefore, I return the value I just sent. However, this does not seem to work.

What I get returned is:

Take note that the value of decoded output is empty.

Is there a way to let the SET-Function output the value it just assigned?

Answer 1

You can try events, check this out: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html?highlight=events#events

Answer 2

The value is actually returned, but we just don't have a way to get it with web3 libraries yet. Think about it: how can your client get the return value if it has no clue when or if the transaction will be included in a block.

Luckily for you, there's a solution. It's called "Events", check it out: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html?highlight=events#events