[Ethereum] How to convert string to bytes32 properly

bytes32solidityweb3js

In my solidity I'm using a mapping like this:

mapping(bytes32 => uint) items;

constructor() {
   items["test"] = 2;
}   

function getItem(bytes32 key) returns(uint) {
   return items[key];
}

My question is now how to call the function in JS using web3 1.0? I have to convert the string to hex. Using web3.utils.stringToHex("test") gives me 0x74657374. Using that I'm getting invalid bytes32 value. The function web3.utils.asciiToHex returns 0x7465737400000000000000000000000000000000000000000000000000000000 which looks for me like a different value. The function call succeeds but I don't get the expected result value of 2.
I also tried web3Utils.padLeft(web3Utils.stringToHex(params[index]), 64); which gives 0x0000000000000000000000000000000000000000000000000000000074657374. Function call succeeded but result value is also 0 not 2.

Best Answer

If you're on web3 v0.x, then:

Use web3.fromAscii before you send the string to the smart contract
Use web3.toAscii after you read the string from the smart contract

If you're on web3 v1.x, then:

Use web3.utils.asciiToHex before you send the string to the smart contract
Use web3.utils.hexToAscii after you read the string from the smart contract

Related Solutions

Solidity – VM Exception: Invalid JUMP When Calling a Second Function

You need to add the constant keyword to the test() function like:

pragma solidity ^0.4.0;
contract Test {
    mapping (address => uint256) weismap;

    function bet(uint vote) payable returns (uint256 weis) {
        if (msg.value==0) 
            throw;
        weismap[msg.sender]= msg.value;
        return  weismap[msg.sender];
    }

    function test() constant returns (uint myVote)  {
        return 1;
    }
}

Calling bet(...) with the value 2. Note that I'm sending 2 ethers as well with the transaction:

Now I call test() AND I've left the value 2. This call to test() fails as the constant function is being called as a transaction, not a read of the values off the blockchain:

If I call test() AND I've set value to blank, this call to test() succeeds as the constant function is being called as a read of the values off the blockchain:

Web3.js Go-Ethereum – sendRawTransaction Hex String Error

As mentioned in the comments, add a 0x to your serializedTx.toString('hex').

Best Answer

Related Solutions

Solidity – VM Exception: Invalid JUMP When Calling a Second Function

Web3.js Go-Ethereum – sendRawTransaction Hex String Error

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