contract state variable does not change after call the function

Question

I have deployed the contract, the code is here, very easy. Then get the instance ballot1 = eth.contract(abi).at(addr) call the function ballot1.giveRightToVote.sendTransaction(eth.accounts[1], 'xiaoB', {from:eth.accounts[0]}) continue minned after confirmed

ballot1.voters() ["0x0000000000000000000000000000000000000000000000000000000000000000", false, 0, 0, 0]

the state variable was still empty

Answer 1

Try calling ballot1.voters(eth.accounts[1]) instead of just ballot1.voters(). Explanation follows.

When you mark a variable public, solidity creates getter functions, so for example if you make a variable called address public my_address, it will make the equivalent to:

function my_address() constant returns (address) {
   return my_address;
}

You're trying to use such a getter function for voters. However, voters is a mapping, which is a list of keys (in this case of type address) to values (of type Voter). You might expect that it would have a auto-generated a function so that called without parameters, it would return all the keys to the mapping, or maybe the keys and their values. However, you can't iterate a mapping; There is no way to get the keys in solidity unless you already know them, so the Solidity compiler can't do anything sensible with just a call to a public mapping with no arguments. What it's done instead is to auto-generate a function with an argument for the key. When you're calling it without a parameter, it's imagining you called it with the parameter 0x0000000000000000000000000000000000000000000000000000000000000000, which returns an empty mapping since you haven't set any values for a voter with the address 0x0000000000000000000000000000000000000000000000000000000000000000.

If you do need to iterate through the keys of voters, what you can do is create a parallel data structure in the form of an array called voter_addresses[], make that public, and set it at the same time as you set a value in the voters mapping. If you mark that public, you should (IIRC) be able to get the resulting array by calling voter_addresses().

Answer 2

I modified your code just to change the Solidity version to match my environment:

pragma solidity ^0.4.2;

contract Ballot {
    // 投票人结构体
    struct Voter {
        bytes32 name;
        bool voted;  // 是否已经投过票
        uint vote;   // 投给谁了
        uint givenRightTime; // 被授权时间
        uint votetime; // 投票时间
    }

    // 候选项结构体
    struct Proposal {
        bytes32 name;
        uint voteCount;
    }

    address public chairperson;  // 投票发起人

    mapping(address => Voter) public voters; // 投票群众

    Proposal[] public proposals;  // 候选选项

    event voteCast(address from, bytes32 proposal, uint voteTime);

    // 构造方法
    function Ballot(bytes32[] proposalNames) {
        chairperson = msg.sender;

        // 初始化候选项
        for(uint i = 0; i < proposalNames.length; i++) {
            proposals.push(Proposal({
                name: proposalNames[i],
                voteCount: 0
            }));

        }
    }

    function giveRightToVote(address voter, bytes32 voterName) {
        // 如果不是投票发起人分配，或者分配的地址已经投过，抛异常
        if(msg.sender != chairperson || voters[voter].voted) {
            //throw;
        }
        voters[voter].name = voterName;
        voters[voter].voted = false;
        voters[voter].votetime = 0;
        voters[voter].givenRightTime = now;
    }

    // 投票
    function vote(uint proposalIndex) {
        Voter sender = voters[msg.sender];
        // 检查是否已经投过
        if(sender.voted) {
            throw;
        }

        proposals[proposalIndex].voteCount += 1;

        // 修改状态
        sender.voted = true;
        sender.votetime = now;
        sender.vote = proposalIndex;

        voteCast(msg.sender, proposals[proposalIndex].name, now);
    }

    // 获取获胜者编号
    function winningProposalIndex() constant
            returns (uint winningProposalIndex)
    {
        uint winningVoteCount = 0;
        for (uint p = 0; p < proposals.length; p++) {
            if (proposals[p].voteCount > winningVoteCount) {
                winningVoteCount = proposals[p].voteCount;
                winningProposalIndex = p;
            }
        }
    }

    // 获取获胜者姓名
    function winnerName() constant
            returns (bytes32 winnerName)
    {
        winnerName = proposals[winningProposalIndex()].name;
    }
}

And loaded your code into Browser Solidity, connected to my --dev geth instance with eth.accounts[0] unlocked.

I executed the transaction giveRightToVote(...) with the parameters "0x0014060ff383c9b21c6840a3b14aab06741e5c49","xiaoB" where the address is my eth.accounts[1].

The then called the autogenerated function voters(...) with the parameter "0x0014060ff383c9b21c6840a3b14aab06741e5c49" and it returned the expected results:

In geth, I confirmed the returned value from voters(...) using the command:

> web3.toUtf8("0x7869616f42000000000000000000000000000000000000000000000000000000")
"xiaoB"

I then ran the following in geth:

> var abi = [{"constant":false,"inputs":[{"name":"proposalIndex","type":"uint256"}],"name":"vote","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"proposals","outputs":[{"name":"name","type":"bytes32"},{"name":"voteCount","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"chairperson","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"winningProposalIndex","outputs":[{"name":"winningProposalIndex","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"address"}],"name":"voters","outputs":[{"name":"name","type":"bytes32"},{"name":"voted","type":"bool"},{"name":"vote","type":"uint256"},{"name":"givenRightTime","type":"uint256"},{"name":"votetime","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"winnerName","outputs":[{"name":"winnerName","type":"bytes32"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"voter","type":"address"},{"name":"voterName","type":"bytes32"}],"name":"giveRightToVote","outputs":[],"payable":false,"type":"function"},{"inputs":[{"name":"proposalNames","type":"bytes32[]"}],"type":"constructor","payable":true},{"anonymous":false,"inputs":[{"indexed":false,"name":"from","type":"address"},{"indexed":false,"name":"proposal","type":"bytes32"},{"indexed":false,"name":"voteTime","type":"uint256"}],"name":"voteCast","type":"event"}];
undefined
> var addr = "0x0d41ff746994e76fd0ad575ca852e447559e8089";
undefined
> var ballot1 = eth.contract(abi).at(addr);
undefined
> ballot1.giveRightToVote.sendTransaction(eth.accounts[2], 'account2user', {from:eth.accounts[0]});
"0x07c24de5b92499f05570a2c648bc8f30ae7a23676bddf29ad00aea4a8b21da58"
// Wait for the transaction to be mined, then check it worked correctly
> eth.getTransactionReceipt("0x07c24de5b92499f05570a2c648bc8f30ae7a23676bddf29ad00aea4a8b21da58")
{
  blockHash: "0xf11c183e434266199912cfbb97984c7a527f0c0858dd238dd5bca290cf8c4190",
  blockNumber: 30084,
  contractAddress: null,
  cumulativeGasUsed: 74723,
  from: "0x000d1009bd8f0b1301cc5edc28ed1222a3ce671e",
  gasUsed: 74723,
  logs: [],
  logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
  root: "0x6095d7e4c505418b78d12034270b4d88c27d4921c71cbd1767d525cb3c8c5319",
  to: "0x0d41ff746994e76fd0ad575ca852e447559e8089",
  transactionHash: "0x07c24de5b92499f05570a2c648bc8f30ae7a23676bddf29ad00aea4a8b21da58",
  transactionIndex: 0
}
> ballot1.voters(eth.accounts[2]);
["0x6163636f756e7432757365720000000000000000000000000000000000000000", false, 0, 1482575492, 0]
> web3.toUtf8("0x6163636f756e7432757365720000000000000000000000000000000000000000");
"account2user"

Your code is working as expected. Just follow the steps above. As @Edmund Edgar has stated, you will need to pass the account parameter to ballot1.voters(...).

---

Update Responding To Comment Below

1. As you are sending your transaction from from eth.accounts[0], you only have to unlock eth.accounts[0].

2. You may want to try Browser Solidity - it's a bit easier to interactively work out what is going on. To do this:

   • Point your browser to https://github.com/ethereum/browser-solidity.
   • Change Branch on the top left from master to gh-pages.
   • Download the .zip file onto your computer. The current .zip file has the name browser-solidity-6698a74.zip.
   • Unzip the .zip file into a subdirectory on your computer.
   • Navigate to the new subdirectory.
   • Load index.html in this subdirectory in your web browser.
   • In Browser Solidity, select the cube icon on the top right.
   • Click on Web3 Provider and confirm that you want to connect to your local Ethereum node.
   • Load your Solidity code in the left pane.
   • Click on the Create button after specifying your contract's constructor parameters on the input box to the right of the Create button.
   • Click on the giveRightToVote button after specifying the parameters - see the screenprint I've attached.
   • Click on the voters button after specifying the parameters - see the screenprint I've attached.

Answer 3

I have solved the question by adding the parameter gas ballot1.giveRightToVote.sendTransaction(eth.accounts[2], 'account2user', {from:eth.accounts[0], gas: 4700000}); but while I called the function at the second time as above ballot1.giveRightToVote.sendTransaction(eth.accounts[3], 'account3user', {from:eth.accounts[0]}); without gas, it successed too. Really unimaginable