8

While the return value of a function call executed on-chain cannot be returned off-chain, you can however simulate a function call on-chain to see what that function call would return. In ethers, you can use callStatic. From ethers' documentation: Rather than executing the state-change of a transaction, it is possible to ask a node to pretend that a call is ...


7

Declaring a function as external rather than public does not affect gas usage at all, neither in contracts nor in libraries. In earlier versions of Solidity only external functions could take calldata arguments. Making a function public would force you to use the more expensive memory arguments. This restriction was lifted in Solidity 0.6.9. This is probably ...


4

That is not going to make a difference, bots are looking for pending transactions that execute the addLiquidity method. In order for that to work, the addLiquidity method on the router contract needs to be executed. Whether it is executed directly or via a proxy contract, it does not matter because the method on the router contract is always executed and ...


4

Your theory is correct. MetaMask sends a static (local) call to the contract. The call is the same as a real transaction, except 1) its state changes are not persisted 2) it doesn't cost any gas, since it doesn't send a transaction to the blockchain 3) is executed against your local node's data only. That way is not 100% accurate, but it's basically the best ...


3

modify your build.gradle to this and rebuild (i usually use maven), the problem was probably with okhttp used in web3j dependencies { // https://mvnrepository.com/artifact/org.web3j/core implementation 'org.web3j:core:4.8.4' implementation 'org.springframework.boot:spring-boot-starter-web' testImplementation 'org.springframework.boot:spring-...


3

Ran into the same problem. Looking at the code, there seems to be a hardcoded timeout to 5 seconds.


3

A more modern style, as the last answer has gone a bit out of date: (tokenInAfterFee, tokenOutAmt) = spclContract.swap{value: msg.value}(_spctToSwap); (edit: the accepted answer was edited after I posted this to match mine. Not sure that's a good idea, it's good to have access to old code as well... Anyways...)


3

The factory contract - PancakeFactory - is here: https://bscscan.com/address/0xcA143Ce32Fe78f1f7019d7d551a6402fC5350c73 If you read the contract, you'll see that allPairsLength gives you 14,690 pairs. This refers to the number of PancakePair-type contracts. The addresses can be found by reading the allPairs array in PancakeFactory by specifying the index you ...


3

You can fork Rinkeby or the Mainnet pretty easily using Ganache-CLI. Read this article for a detailed explanation https://blockheroes.dev/test-smart-contracts-on-mainnet/ The simplest command is: ganache-cli --fork https://eth-rinkeby.alchemyapi.io/v2/{myKey} But you can personalize it by specifying: the block number from where you want to fork an address ...


3

The hexadecimal equivalent of the method is called the function selector. The function selector is the first 4 bytes of Keccak hash of the function signature, arguments packed as string types. You can get this by: >>> from web3 import Web3 >>> Web3.keccak(text="xyz()") HexBytes('...


2

Think of it like this, Who call the function/initialize a transaction will pay for the gas fee A smartcontract's function can not just run by itself, either another smartcontract or an EOA must call it first which means that the first one to call a smartcontract's function must be an EOA, because no smartcontract's function can call another smartcontract's ...


2

I think the question is too general in nature so the only possible answer is "it depends." The right way to structure the contract depends on what the contract is supposed to do. Deployment is a specific step in the lifecycle of the contract. What needs to happen at that stage? For example, it might be unacceptable to have an instance of the ...


2

Not sure what library you're using. They are usually designed to fail on an overthrow or underflow. For example: require(total >= arg1); It is probably because lastYearsTotalSupply == 0 which will cause division to fail. Another possibility is the inputs are so large it is causing multiplication to overthrow. In case the library has functions like ...


2

What's the need so that some dapp websites ask you to sign messages It establishes that the signer knows the private key for a given ethereum address. For example, Etherscan will let you configure the website, social media links, logo, etc., for a given contract, but first you have to show that it's your contract by signing a message from the same account ...


2

Yes. You can use the getCode API. If that call returns 0x, there is no contract at that address. If it returns anything other than 0x, there is a contract at that address. As an example: web3.eth.getCode("0xd5677cf67b5aa051bb40496e68ad359eb97cfbf8") .then(console.log); > "...


2

I don't know of any template, but this can be done relatively easily with solidity. Consider the dummy code below: pragma solidity ^0.8.0; /*your code here*/ // private function because it simply calculates commission and pays out accordingly. // Inputs & other validation likely will come from somewhere else in the contract. function takeCommission(...


2

You can use https://bscscan.com/ for Binance Contracts. You can use https://etherscan.io/ for Ethereum Contracts. Here pancakeswap: https://bscscan.com/token/0x0e09fabb73bd3ade0a17ecc321fd13a19e81ce82


2

to push item to array use .push() on array , in this way it's semms to work : myArray.push(i*2); ;)


2

you are looking for this: encodeFunctionSignature web3.eth.abi.encodeFunctionSignature(functionName); Encodes the function name to its ABI signature, which are the first 4 bytes of the sha3 hash of the function name including types. https://web3js.readthedocs.io/en/v1.2.11/web3-eth-abi.html In pythhon there should exist an equivalent call


2

There is no one way which is absolutely better. By using an external visibility modifier, you declare intention that the function should only be used by external parties. In my opinion, using that internally with this.function() is a hack and goes against the original intention. By changing it to public, you declare intention that the function may be used by ...


2

Check out this function I modified from the openzepplin's Address.sol. function _delegatecall(address target, bytes memory data) internal returns (bytes memory) { (bool success, bytes memory returndata) = target.delegatecall(data); if (!success) { if (returndata.length == 0) revert(); assembly { revert(add(32, returndata), ...


2

This took a fair amount of playing around, but finally discovered that: await NFT.connect(sender)['safeTransferFrom(address,address,uint256)']( sender.address, recipient.address, ethers.BigNumber.from("1") ); is the winning combination. Don't put a . after connect(sender).


2

The minimum gas value for a transaction is 21000 (e.g. simple Ethereum transfer). Any additional (such as calculations / read /store /... operation) will incur additional costs. These operations should be priced according to the cost they impose on node operators. From the Whitepaper: The intent of the fee system is to require an attacker to pay ...


2

You have to listen to the contract events. "mint" function is done by the standards that should emit the Mint event. And then you can do something like this: contract.events.allEvents() .on('data', (event) => { console.log(event); }) .on('error', console.error); There are many manuals out there for "listen for smart contract events&...


1

If the function name and parameters are known it should be possible to create a dummy contract and generate a minimal ABI with Remix. Then use Remix connected to Metamask or a wallet like MyEtherWallet and MyCrypto.


1

It does not work because as you said A and B addresses are not stored in B and A. The exemple you linked his about compilation and importing, and cannot works in test (infinite loop and no setup for a and b values). Something like that should do the trick for the setup but be aware that the infinite loop is still present contract InterfaceOfA { ...


1

You can call the Uniswap's contracts directly. Specifically, you should call the Router02 contract, which handles all the details. Depending on your use case, you need to decide which function to call, since there are many variants. You can find the documentation at https://uniswap.org/docs/v2/smart-contracts/router02/ You will need some way to create a ...


1

Your contract needs to allow the transaction sender to spend CHI tokens belonging to the contract. To do this, the contract has to call approve method of the CHI token contract, which can be problematic because you'd have to code a method that does that. Thus, it's better to use freeUpTo which spends msg.sender's tokens. Proof: function freeFromUpTo(address ...


1

This will essentially depend on the national/local legislation from which the law is applicable to such an asset. In general terms, as of today, the answer is NO unless there is an underlying contract signed by a public notary to validate the ownership of the asset through an NFT. If this is not granted, a theft of that physical asset can't be legally ...


1

View Smart Contract Function Calls With Bloxy Search for the smart contract using its' address with Bloxy. i.e. 1inch smart contract address: 0x111111111117dC0aa78b770fA6A738034120C302 Scroll down to the Smart Contract Function Calls section to view all smart contract function calls made. FYI - It seems 1inch never called renounceOwnership, therefore an ...


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