[Ethereum] ethers.js pass address as parameter. How to encode

abisolidity

My question is pretty simple

I'm trying to call a function in my smart contract from ethers.js

I just need to set a variable of type "address" in my contract.

Code:

//solidity
function setTokenX(address _tokenX) public {
    tokenX = _tokenX;   
}

//js

tokenX = '0x3fdaf6c54eba05edebed44c4f986f49a5de55113';

await mycontract.setTokenX(tokenX);

It works a weird way for some reason. On Etherscan my variable is displayed as

0x361d47ce0000000000000000000000003fdaf6c54eba05edebed44c4f986f49a5de55113

While in the in javascript I send the parameter as a string. What's the catch? Should I encode it and then abi.decode in solidity? How to do this with ethers.js?

Best Answer

The contract should be working correctly.

The input look a little odd because it is encoded in the solidiy ABI.

0x361d47ce0000000000000000000000003fdaf6c54eba05edebed44c4f986f49a5de55113

361d47ce The first four bytes is the function selector. It encodes the function to be called.
0000000000000000000000003fdaf6c54eba05edebed44c4f986f49a5de55113 The next 32 bytes is the address parameter padded to with zeros.

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Solidity – How to Return a String with Function in Solidity 0.5.1 Without Errors

In v 0.5, explicit data location for all variables of struct, array or mapping type is now mandatory. Please note that strings and bytes also belong to the array implementation.

Hence your code must be modified as shown below to work with v0.5:

pragma solidity ^0.5.1;

contract and {

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solidity Warning – Silencing Unused Function Parameter Warning in Solidity

You will see the same warning in Remix if you look at the compiler page.

The warning is quite clear: you have a variable which is not used anywhere in the function logic. It's not an error but the compiler is trying to help you to save gas and to make the function cleaner by removing the unneeded parameter. If you want you can just ignore the warning.

There is a curious feature that if you remove the variable name the warning disappears. But the function still has the same signature. I actually don't know why such a thing has been implemented.

Best Answer

Related Solutions

Solidity – How to Return a String with Function in Solidity 0.5.1 Without Errors

solidity Warning – Silencing Unused Function Parameter Warning in Solidity

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