How to implement staking function?
I can't find a smart contract with staking function.
Give me please some examples.
Related
I am planning to issue erc20 token on ethereum and I want to use it as a payment for dapps on polygon.
How may I estublish the interaction between the contracts? A potential answer to that question might be bridging. But I tried to look for every platform to understand, how can I use my coin tokens after bridging, but failed to find any definite answer.
so my question is, if two contracts are on the same chain-
IERC20 token = IERC20(some_address);
We use the above line to call our coin token from our dapp. Since, our coin token is on different ethereum chain, after bridging, how do we call it feom a contract that will be deployed on polygon?
Will the above line of code work? Will I get a new address on polygon for my token contract?
(Recently I have seen a technique, but couldn't understand the underlying mechanism. So, there is a website called Coinvise, they let you deploy your coin airdrop contract on polygon and let you set the nft address (to know if user holds that particular nft) as eligibility condition that is deployed on ethereum. They do it on chain using something called 'sub-graph'. I do not know what this is but I'd like to know if it helps in my case.)
I am new to blockchain, please help
My ultimate purpose is to swap some tokens across pancakeswap babyswap apeswap atomicly. So I build a contract(called ContractA) to run a bunch of swaps in a transaction. I transfer some USDT token into ContractA. But ContractA is not approved to transfers USDT by the USDT contract.
I known how to approve Metamask address to transfer USDT, but how to do it for a Contract?
In order to control an ERC20 token from a smart contract, first you need to create an instance of it. To do that, first you need to import ERC20 to your contract, and then just create an ERC20 type function giving it the token address you want to manage. It would be something like this:
// Some code...
import "#openzeppelin/contract/token/ERC20/ERC20.sol";
// Some more code...
contract exampleContract {
// Example of an ERC20 token instance
ERC20 USDTToken = ERC20("USDT Contract Address Here");
// Approve USDT
USDTToken.approve(address(this), _amount);
}
Then you will be able to manage the token, always following the ERC20 standard, as you want.
Hope you find this information useful :)
I have a smart contract that inherits VRFConsumerBase in order to get random numbers. I need users to call functions that will request randomness, but in order to do that the contract must have some LINK. When someone funds the smart contract with LINK anyone can spend it afterwards by calling a function that will request randomness. How can I make that only the person that funded enough LINK to the contract can call those functions.
How do I make a existing running erc20 to prevent some holders from transacting?
I am trying to do a staking feature. Can I write a new contract to control the existing erc20 contract?
Logic that would affect a token holder's ability to transfer (or have a party transferFrom on the holders behalf) must be written into the contract if you want token transfers to be halted within the contract itself. Therefore, if you already have a contract deployed you would have to deploy a new ERC20 contract that has the logic - if you want the staking mechanism to be within the same contract. Then you would have to transfer balances from the previous version of the contract to the newly deployed contract. While possible, it would incur a gas expense to replicate the contract state. You could have your token holders pay this gas cost by having some sort of mint or recover function that would read the old contract balance for an address, create the balance on the new contract, and then mark the balance as transferred.
Alternatively, to your second question, you could facilitate the staking with an additional contract that users would set an allowance to within the ERC20 contract. Then, users could interact with something like a stake function on this new staking contract. The staking contract would use the transferFrom ERC20 function to transfer tokens from the owner to the staking contract's address after incrementing the user's staked token amount within the staking contract. This would record the holder's staking "credit" and tie the tokens up by transferring their ownership to the staking contract. Users could then unstake which would decrement the user's staked token amount and transfer the tokens back from the staking contract's address to the token holder's address. This type of approach has more moving pieces but could be a more flexible step while developing the mechanism as you can deploy new versions of the staking contract without having to redeploy the ERC20 contract or transfer balances. Users would be able to transfer like normal throughout multiple versions of the staking contract and extracting tokens from previous versions of the staking contracts would be gas-efficient.
I am a beginner in writing smart contract. I want to deploy a crowdsale and token contract on the Kovan testnet. Everything works well except when I tried to send KTH to the crowdsale contract. I always get "reverted transaction" in the end. Could someone help me solve this situation? I am using the standard Crowdsale and Token sale contract from openZeppelin and truffle suite.
Crowdsale contract: https://kovan.etherscan.io/address/0x68321f1380ac45be3f3d85d0cd95d1ac5710b8a9#code
Token contract:
https://kovan.etherscan.io/address/0xb76b6ae76cee43e0b32588ffc112efca3c781f1e#code