5

I'm making a subcurrency with solidity. I'm confused at implementing the transfer mechanism.

Here's my code:

function SubCoin(){
      balances[msg.sender] = totalPoints;
}

function send(address to, uint256 valueInmWard) {
    if (balances[msg.sender] >= valueInmWard) {
      balances[to] += valueInmWard;
      balances[msg.sender] -= valueInmWard;
      PointTransfer(msg.sender, to, valueInmWard);
    }
  }

I'm stuck at setting the msg.sender address. I only know I can use: web3.eth.defaultAccount = web3.eth.coinbase; to send from eth.accounts[0]. I call SubCoin.send.sendTransaction(web3.eth.accounts[1], 1000); in web3 to perform the action.

If I would like to send among eth.accounts[1], eth.accounts[2]..., how should I specify the msg.sender in web3?

5

sendTransaction expects an optional transaction object as first parameter after the method arguments. Among other things this allows you to specify the sender address via the from attribute.

Example:

var tx = {from: web3.eth.accounts[1]};
SubCoin.send.sendTransaction(web3.eth.accounts[0], 1000, tx);

The same transaction object can not only be passed to contract.method.sendTransaction but also to contract.method.call, web3.eth.sendTransaction, and web3.eth.call.

More information can be found in the documentation.

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  • Hi, I'm studying DAPP. I have a question.. How can it be allowed changing msg.sender parameter from who calling api? Is it possible on main network? I'm confused how it can be safe.. – yountae.kang Oct 23 '18 at 1:54

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