openzeppelin-contracts | OpenZeppelin Contracts is a library for secure smart contract development | Blockchain library
kandi X-RAY | openzeppelin-contracts Summary
kandi X-RAY | openzeppelin-contracts Summary
A library for secure smart contract development. Build on a solid foundation of community-vetted code. :mage: Not sure how to get started? Check out Contracts Wizard — an interactive smart contract generator.
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QUESTION
The openzeppelin minimal proxy contract here has this function predictDeterministicAddress() that hashes values like the sender's address, a salt... to generate a contract address that the create2 function will also generate, when its passed the same values as dictated in this EIP.
This EIP states that an arbitrary value 0xff when hashed with a salt, senders address and the contract bytecode will always generate the same address.
Im trying to implement the predictDeterministicAddress() function on TRON blockchain but the TRON docs specify a different arbitrary value, 0x41 for implementing this same feature.
I tried to just replace the values but i can't see where the openzeppelin team used the value 0xff in their function.
Below is the openzeppelin hashing function:
ANSWER
Answered 2022-Mar-23 at 03:33According to solidity's official documentation (https://docs.soliditylang.org/en/latest/control-structures.html?highlight=create2#salted-contract-creations-create2), the algorithm for calculating create2 addresses should be as follows:
QUESTION
I have the following import statement in a Solidity contract ( this works).
...ANSWER
Answered 2022-Mar-18 at 22:02Your snippet shows a direct import that searches for the file in your local directories based on the compiler config.
One of the default sources is the node_modules directory where NPM packages are installed.
The @ symbol is just a prefix of NPM scoped packages, allowing to group more packages into the same namespace (in this case @openzeppelin/).
To import a contract from GitHub, you can just pass its full URL:
QUESTION
I'm trying to use my custom ERC20 contract that is stored in my local storage in the SWAP project that I'm working on.
the error I'm getting while trying to use the erc20 import inside the SWAP contract:
...ANSWER
Answered 2022-Mar-04 at 15:42Change
use erc20::Erc20;
to
use erc20::Erc20Ref;
Put this at the top of the ERC20 contract:
pub use self::erc20::{Erc20, Erc20Ref};
You can see an example of this in the subber contract where it specifies itself as SubberRef and is then called from the main delegator contract
QUESTION
*****top lines of my .sol file // SPDX-License-Identifier: MIT pragma solidity ^0.8.0;
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
contract ParcelAsset is ERC721 {
******command line VScode brownie compile contracts\ParcelAsset.sol
I get this error. ValueError: Invalid NPM block in '>=0.6.0 <0.8.0 import "@openzeppelin/contracts/token/ERC721/ERC721.sol"': 'import'
*********** snippet of my brownie-config.yaml dependencies:
- smartcontractkit/chainlink-brownie-contracts@1.1.1
- OpenZeppelin/openzeppelin-contracts@3.4.0
compiler:
solc:
remappings:
- '@chainlink=smartcontractkit/chainlink-brownie-contracts@1.1.1'
- '@openzeppelin=OpenZeppelin/openzeppelin-contracts@3.4.0'
I have tried npm install @openzeppelin/contracts and upadating solidity to 0.8.0
Anyone known what I am doing wrong?
...ANSWER
Answered 2022-Feb-10 at 20:08I solved it by doing: npm install @chainlink/contracts --save
I personally didn't bother importing openzeppelin because all safemath functionalities (if that is what you are importing) are already implemented into solidity 0.8.0, so if you're using solidity 0.8.0, the safemath library is obsolete
QUESTION
I tried all that you mentioned in the discussion here (in other questions) and at https://github.com/smartcontractkit/full-blockchain-solidity-course-py/discussions/522 , however it is not solving the issue for me, I also noticed that the current compiler version remains (current compiler is 0.6.12+commit.27d51765.Windows.msvc). But when I right click and select Solidty:Compiler information, it shows 0.8.0.
from output:
...ANSWER
Answered 2022-Jan-02 at 03:09i had the same issue. i had this compiler setting:
QUESTION
What I am trying to achieve is calling a transferFrom from ERC20 contract inside an ERC721 contract like this:
My ERC20 contract:
...ANSWER
Answered 2022-Jan-11 at 14:03In order to interact with an ERC20 token, you have to create an instance of it from the desired contract. You would need to import ERC20 to your nfts contracts, and then create an ERC20 token instance pointing to your token. It would be something like this:
QUESTION
I am very new to Solidity, and have recently been working on trying to learn the ropes. For reference, I have been using code from this video (https://www.youtube.com/watch?v=tBMk1iZa85Y) as a primer after having gone through the basic crypto zombies tutorial series.
I have been attempting to adapt the Solidity contract code presented in this video (which I had functioning just fine!) to require a Burn of a specified amount of an ERC-20 token before minting an NFT as an exercise for myself. I thought I had what should be a valid implementation which compiled in Remix, and then deployed to Rinkeby. I call the allowAccess function in Remix after deploying to Rinkeby, and that succeeds. But, when I call the mint function with the two parameters, I get: "gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? execution reverted."
If I still send the transaction, metamask yields "Transaction xx failed! Transaction encountered an error.".
I'm positive it has to do with "require(paymentToken.transfer(burnwallet, amounttopay),"transfer Failed");", though I'm not sure what's wrong. Below is my entire contract code. I'm currently just interacting with the Chainlink contract on Rinkeby as my example, since they have a convenient token faucet.
...ANSWER
Answered 2022-Jan-14 at 18:56I'm not sure why are you trying to burn link in order to mint and nft but first check if the link code does not have a require that check if the destination address is the burn address if it has then burn the link is not possible and you should use any other erc20 maybe your own erc20, also your contract probably does not have any link and if you want to transfer the link from the user you should do this in the contract paymentToken.transferFrom(msg.sender,destinationAddress,amount) and if the user previously approve your contract you will able to send the tokens, and i suppose that the purpose of the allowAccess function is to make the user approve the contract to move the tokens that will never work, the approve function let's anyone that call it approve any address to move an amount of tokens, the thing is that to know who is approving to let other to move the tokens the function use msg.sender to explain how this work take a look at this example
let's say that your contract is the contract A and the link contract is the contract B
now a user call allowAccess in the contract A, so here the msg.sender is the user because they call the function
now internally this function call approve on contract B, here the contract A is the msg.sender, because the contract is who call the function
so what allowAccess is really doing is making the contract approving itself to move their own tokens that I assume it doesn't have
QUESTION
I'm pretty new to programing in solidity and I'm currently trying to run a simple smart contract in Remix, seen bellow:
...ANSWER
Answered 2022-Jan-04 at 20:41fix constrcutor
QUESTION
I have taken different courses and even tho they explain how to make a token I haven't been able to learn how to implement tokenomics.
For example fees for transactions, burning to LP etc...
I leave a link to the openzeppelin standard
Would be great to have some more detailed examples on it.
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol
...ANSWER
Answered 2021-Dec-11 at 22:16What you are looking for is to make a custom _transfer() method by overriding the one provided in the OpenZeppelin ERC20 standard.
You can check with the "OXB" (oxbull.tech) token, which implements this type of fee, but basically you just take tokens from the sender before sending them to the receiver, and once you are done charging the fees you can send the remaining tokens to the receiver.
An example would be:
QUESTION
I have two contract that are separately deployed.
FirstContract.sol
...ANSWER
Answered 2021-Nov-18 at 15:46FirstContract derives from ERC721 but your link at the end of the question points at ERC20 contract. So the definition of transfer() in the ERC20 is not relevant in this context.
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