I'm looking to build a ethereum private blockchain, and will like to only restrict a particular user or ip address that can upload smart contracts to our chain.
Is that possible?
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I want to deploy my own ERC-20 token on different blockchains, so is there any possibility to deploy the same token contract on different blockchains. If we do that we can't give the same name and symbol for three blockchains. can anybody tell me what is the solution for this problem? Or can we deploy the contract with the same contract address on three blockchains?
can we deploy the contract with same contract address on three blockchains.
It depends on the network that you're deploying to and the address that you're deploying from. Assuming that the networks of your choice have the same 1) address format and 2) calculation of deployed contract address - then yes, you'll be able to deploy your contract on the same address on multiple networks.
For example Ethereum and BSC do have both of these features. But even though Tron network supports EVM-compatible smart contracts, it has a different way to calculate its addresses, so it won't be possible to deploy your contract on Tron network with the same address as on Ethereum or BSC.
The key to deploy the contract to the same address on multiple networks, is to deploy from the same address, and using the same params:
In case of the regular CREATE opcode, the transaction deploying the contract needs to have the same nonce (and the same from) value across all networks.
Or if you're using the CREATE2 opcode, you need to pass the same contract bytecode, the same salt (to the CREATE2), and again, you need to send the deploying transaction from the same address.
If we do that we can't give the same name and symbol for three blockchains
It is technically possible, so I'm assuming it's "just" a limitation of your business case or some tool that you're using, or a possible simple misunderstanding of how the ERC-20 standard works.
pragma solidity ^0.8;
contract MyToken {
string public constant name = "MyToken";
string public constant symbol = "MyT";
// TODO rest of your token contract source code
}
I have create a Voting Dapp using web3j and ganache, but their is a small problem. I decide to deploy a voting contract every time a new election begin, and there will be a administrator who control the deploy of the contract and the begin and end of the election. So when the voting contract is deployed, only can the administrator get the contract contract address. how can I send the address to normal citizens so they can call the smart contract.
I thought of storing the contract address in a normal database, but if the database is hacked or destroyed, the whole dapp would crash.
Is there any function in web3j that I can store a string in the blockchain itself?
ps. I saw the web3j.dbputString function but I have no idea how to use it.
private String deployContract(Web3j web3j, Credentials credentials) throws Exception {
return Election.deploy(web3j, credentials,GAS_PRICE,GAS_LIMIT).send().getContractAddress();
}
here is the contract deployed segment.
A common design pattern is called Factory. You can have a smart contract that deploys other contracts. This will generate an event that is visible to the user. See Uniswap Factory.
Alternative you can just make the contract constructor to evit an emit and that is caught by the user frontend.
Learning Solidity along with token development.
I'm having a hard time understanding how tokens with multiple smart contracts interact with each other.
I've read through other tokens with multiple contracts on GitHub and reviewed contracts on OpenZeppelin but they all appear somewhat orphaned.
Let's say we developed a token that has a supply and tracks wallet address to amount using a map. The contract is released and is given an address. Admin or privilege methods are protected via owner address validation. Then we release a second contract that needs to make apply a fee for transactions.
How does the second (token transaction fees) contract interact with the data stored on the first (token contract)? Does the second contract need to also verify ownership?
Any contract on Ethereum can interact with any other contract by using Interfaces. You can call methods from the second contract on the first contract for an ERC20 token as below:
Define ERC20 Interface
interface ERC20 {
function balanceOf(address account) external view returns (uint256);
}
Use the interface and token contract address to call methods on the first contract:
ERC20(tokenContractAddress).balanceOf(0xabcd....);
The similar approach can be used for any contracts
I am currently developing a dapp on ethereum. From what I know msg.sender should has the value of the account who interact with it. However, it keeps the value of the deployer's account.
I am using metamask and solidity ^0.4.24. I am deploying the contact using truffle framework and also Ganache GUI as my virtual node
function getMe() public view returns(address){
return msg.sender;
}
So, I expect this code to return the hash of the account which is interacting with the contract but instead I am taking back the address of the acount which deployed it
msg.sender contains the value of the address of the caller. You must be deploying and interacting from the same account, probably using accounts[0].
I'm a new beginner in the ethereum Blockchain.
I want to implement a smart contract that verifies the authenticity of a user and then send a message to a cloud service (with is the smart contract creator) in case of positive verification to grant access to the user.
My question is it possible for a smart contract to return results of his methods invocation to another blockchain user and how we can do it?
A smart contract cannot make calls outside of the blockchain. i.e., you cannot have it call an http endpoint or something similar.
In ethereum, the usual way of achieving something like this is:
Have the user make a transaction passing relevant data to your smart contract
The smart contract runs whatever verification logic it must on that data
The smart contract logs an Event
You have an ethereum node that your code connects to and listens for these events.