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There is no reasoning in your question for not using this: contract IA { function setNumber(uint n) public; } contract B { IA public a; function setContract(IA _a) public { a = _a; } function setNumber() public { a.setNumber(10); } }


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Public key recovery of an ECDSA signature uses the ECRECOVER operation and costs 3000 gas. If you have the public key you can derive the address and afaik a keccak operation(sha3) costs 30 gas.


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TL;DR receive is a new keyword in Solidity 0.6.x that is used as a fallback function that is only able to receive ether. receive() external payable — for empty calldata (and any value) fallback() external payable — when no other function matches (not even the receive function). Optionally payable. Long Answer Solidity 0.6.x introduced the receive ...


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You can simply view the code of upgradable contracts already deployed to mainnet: BUSD Token AMPL Token USDC Token REP Token TUSD Token SNX Token JRT Token


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I tried the deployed contracts and they work as expected. KombuchaProxy shouldn't update Kombucha contract. It updates its own storage. The whole idea of a proxy is that it contains the data and point to another contract that has the code. To test this in Remix I instantiated Kombucha contract at KombuchaProxy address. Now you can execute Kombucha ...


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That BN stands for BigNumber. It's a JavaScript framework for representing..well...big numbers. If you simply console.log a BigNumber it will give you such internal data of the single BigNumber, such as those length and words. Those are not trivially interpretable. So what you should do it simply .toString() it to get the actual number. It really is just ...


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This is a bug in either web3.js OR the node that you're communicating with. It happens only if the require statement includes an error-message. It happens when the node is Infura, but not when the node is Ganache. Note that your function shouldn't be returning false in either case. Either it returns true, or the function-call reverts.


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That statement doesn't make much sense. In solidity 0.5 gas is the remaining gas. With sub(gas, 34710) it would seem they want to send all the remaining gas minus 34710 to the called contract, but from the comment it appear they want to send at least 34710. The error is trying to say that in solidity 0.6 you have to use gas() as it were a function. I will ...


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Gnosis Multisig Wallet was implemented under solc v0.4.x. If you tried to compile your code, then you would know why this is not possible: _confirmations.push(ownersArr[i]); Because the compiler would to you: TypeError: Member "push" is not available in address[] memory outside of storage. _confirmations.push(ownersArr[i]); ^------...


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I'd like to return to the first issue: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8545/. (Reason: CORS request did not succeed). If you're trying to connect to localhost:8545, I assume that you're trying to connect MetaMask to a local node. Essentially, MetaMask is trying to connect to ...


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Being that departmentEmployees is a dynamic array, this assignment naturally reverts: departmentEmployees[_employeeId] = _employeeId; You can change that variable to a mapping, but then, what's the point in mapping a key to its own value (in your case, _employeeId to _employeeId)? So you probably want to leave that variable as is, and simply change your ...


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