I have a simple solidity smart contract with method like:
function foo(uint a) public {
b = bytes32(1);
emit Event(a, b);
emit Event2(a, b);
}
(full code is here: https://remix.ethereum.org/#optimize=false&version=soljson-v0.4.25+commit.59dbf8f1.js)
and invoke it using web3.js code :
contract = testContract.at('xxxAddress')
// contract.foo(6); // Failed, Why?
//Success
contract.foo.sendTransaction(6, {from: eth.accounts[1]},function(error, result) {
console.log("Got err:", error, ", result: ", result)
}
);
but, why straightforward contract.foo(6) failed? Can any expert explain it?
The call to a function that modifies the blockchain needs to send as a transaction since it requires gas to run. This is why you need to send a transaction and not just call the function. You can find more about it here.
Related
The call methods on a contract deployed to mainnet are erroring with insufficient gas messages.
{
code: -32000,
message: 'err: insufficient funds for gas * price + value: address <address> have 27795556348606292 want 420361420000000000 (supplied gas 894386)'
}
On Kovan network, the call methods are working fine. But on Mainnet they are returning the above.
Since call methods require no gas, I'm not sure what the issue is.
$ truffle(mainnet)> c = await EthText.deployed()
$ truffle(mainnet)> c.dapp_name()
dapp_name is a call method
contract MyContract {
string public dapp_name = "Eth Text";
What would cause this error?
I'm trying to implement an upgradable function through delegation. Essentially, the fallback function of contract A is implemented in such a way that when calling function F on contract A, the execution is delegated to function F (same function signature( on contract B.
Callback function looks like this
function() external payable {
address delegate = delegates[msg.sig];
require(delegate != address(0), "Function does not exist.");
assembly {
let ptr := mload(0x40)
calldatacopy(ptr, 0, calldatasize)
let result := delegatecall(gas, delegate, ptr, calldatasize, 0, 0)
let size := returndatasize
returndatacopy(ptr, 0, size)
switch result
case 0 {revert(ptr, size)}
default {return (ptr, size)}
}
}
I ran into problem when trying to use web3.py to call function F in said contract A. I trie a few different things:
// Case 1
Contract.functions.F().buildTransaction()
^ this caused the web3.py to complain that function F is not in contract A's ABI. So then I thought the fallback function uses msg.sig as function signature, so I tried to pass the signature as "data".
// Case 2
Contract.fallback.buildTransaction({'data': "0x61455567"})
// 0x61455567 == bytes4(keccak256("updateContract(address,string,string)"))
which also didn't work because web3.py says "data" cannot be called when building transaction. Finally, I thought I could pass the data field after building the transaction, so I did:
// Case 3
txn_hash = Contract.fallback.buildTransaction({'gas': 1000000})
txn_hash['data'] = "0x837b4bd1"
This time, web3.py didn't complain but the transaction failed on the blockchain (on Rinkeby testnet).
Any help on how to use web3.py to call a custom fallback function?
You can simply use sendTransaction and then it will go into the fallback function.
web3.eth.sendTransaction({'to': contractAddress, 'from': yourAddress, 'data': "0x61455567"})
EDIT:
You can also sign a transaction locally, reference
Following smart contract works fine in Remix and Ganache. However doesn't work on private ethereum blockchains like Kaleido or Azure. What am I missing. When I call setA it consumes all gas and then fails.
pragma solidity ^0.4.24;
contract TestA {
uint public someValue;
function setValue(uint a) public returns (bool){
someValue = a;
return true;
}
}
contract TestB {
address public recentA;
function createA() public returns (address) {
recentA = new TestA();
return recentA;
}
function setA() public returns (bool) {
TestA(recentA).setValue(6);
return true;
}
}
I tried your contract in Kaleido, and found even calling eth_estimateGas with very large numbers was resulting in "out of gas".
I changed the setValue cross-contract call to set a gas value, and I was then able to call setA, and estimating the gas for setA showed just 31663.
recentA.setValue.gas(10000)(6);
I suspect this EVM behavior is related to permissioned chains with a gasprice of zero. However, that is speculation as I haven't investigated the internals.
I've also added eth_estimateGas, and support for multiple contracts in a Solidity file, to kaleido-go here in case it's helpful:
https://github.com/kaleido-io/kaleido-go
Another possibility for others encountering "out of gas" calling across contracts - In Geth if a require call fails in a called contract, the error is reported as "out of gas" (rather than "execution reverted", or a detailed reason for the require failing).
You are hitting the limit of gas allowed to be spent per block. Information about gas limit is included into every block, so you can check what's this value is right now in your blockchain. Currently on Ethereum MainNet, GasLimit (per block) is about 8 millions (see here https://etherscan.io/blocks)
To fix this, you can start your blockchain with modified genesis file. Try to increase value of gasLimit parameter in your genesis file, which specifies the maximum amount of gas processed per block. Try "gasLimit": "8000000".
Try to discard the return statement of setValue method in contract TestA.
pragma solidity ^0.4.24;
contract TestA {
uint public someValue;
function setValue(uint a) public {
someValue = a;
}
}
I've deployed the ScoreStore contract to test RPC, and it works fine. This is ScoreStore contract:
pragma solidity ^0.4.4;
contract ScoreStore
{
mapping(string => int) PersonScores;
function SetScore(string name, int score) {
if(PersonScores[name]>0){
throw;
}
else{
PersonScores[name] = score;
}
}
function GetScore(string name) returns (int){
return PersonScores[name];
}
}
Now I want to use this contract on another contract named MyGame, the contract code is as follows:
pragma solidity ^0.4.4;
contract IScoreStore{
function GetScore(string name) returns (int);
}
contract MyGame{
function ShowScore(string name) returns (int){
// Interface takes an address of the existing contract as parameter
IScoreStore ss = IScoreStore(0x6c38cfb90e8fb1922e61ea4fbe09d29c7751bf82);
return ss.GetScore(name);
}
}
When I give this command on truffle console, mg.ShowScore.call("Anna")
it thorws this:
Error: VM Exception while processing transaction: revert
at XMLHttpRequest._onHttpResponseEnd (C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\xhr2\lib\xhr2.js:509:1)
at XMLHttpRequest._setReadyState (C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\xhr2\lib\xhr2.js:354:1)
at XMLHttpRequestEventTarget.dispatchEvent (C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\xhr2\lib\xhr2.js:64:1)
at XMLHttpRequest.request.onreadystatechange (C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\web3\lib\web3\httpprovider.
at C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\truffle-provider\wrapper.js:134:1
at C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\web3\lib\web3\requestmanager.js:86:1
at Object.InvalidResponse (C:\Users\Fariha.Abbasi\AppData\Roaming\npm\node_modules\truffle\build\webpack:\~\web3\lib\web3\errors.js:38:1)
Any idea, what i am doing wrong?
Any help is appreciated, P.S: testrpc is already running.
I was able to compile both the contracts in remix and call the ShowScore function after setting some value from ScoreStore contract successfully.
Are you sure the address given to the interface is correct? Because I got the same revert error when I gave an invalid address.
I've just recently finished working on a rather complex contract with the Remix IDE. I'm now attaching web3 to the frontend but when I call functions that should fail, they still go through on Metamask.
When testing my contract in Remix, I would often click on and call certain functions that had require statements that I knew would fail just to confirm that the contract state was recorded correctly. Remix didn't send the transaction to metamask and instead output an error message and I would like to handle the transaction error on my own as well.
How can I check my contract call to see whether it will fail. Must I use the method that predicts gas and detect it that way and if so how? My current code is below:
contract.callFunction(function(error, result) {
if (!error) alert(result);
else alert(error);
}
The above code catches rejecting the metamask confirmation as an error but transactions that should fail go through to metamask with an insanely high gas limit set. The function callFunction is in the contract and takes no parameters but does have an effect on the blockchain so it requires the transaction. The first line of the function is "require(state == 1);" and I have the contract set to state 2 currently so I'm expecting the transaction to fail, I just want to detect it failing.
In order to find out whether the transaction will fail we do have to call estimateGas() and attach a callback function. I assumed we'd have to check the gas estimate returned in order to predict whether it would fail but the process is made rather easy. Here's the full code I ended up with to successfully run a function while catching the two most common error cases.
contract.nextState.estimateGas(function(error, result) {
if (!error) {
contract.nextState(function(error, result) {
if (!error) {
alert("This is my value: " + result);
} else {
if (error.message.indexOf("User denied") != -1) {
alert("You rejected the transaction on Metamask!");
} else {
alert(error);
}
}
});
} else {
alert("This function cannot be run at this time.");
}
});
[EDIT] I'm coming back after the fact to help clear up information for those with a similar question. All of the information discussed below references the following link.
After creating a contract object, you can access any variable or function through using it's name. You can also access these members through array notation which is useful when the name of the variable or function isn't known at the time the code is written.
contract.foobar == contract["foobar"]
Once you have a function object (contract.foobar) you can use either call, send, or estimateGas. After first giving the function the parameters it needs (call it like any other function) you then use either call, send, or estimateGas on the returned object while providing options and a callback function.
This callback function takes 2 parameters. The first is the error which will be undefined if there was no error, and the second will be the result of the call, send, or estimateGas. Call and Send will both return the result of the function while estimateGas always returns a number showing how much gas is estimated to be necessary.