5
Your assumptions are correct, it needs to be public but modifiers can help in this case. ChainlinkClient has recordchainlinkfulfillment modifier for fulfillment callbacks.
This modifier specifies that only the original oracle that was called may call this function, the oracle defined when you send the request.
Reference: chainlink docs
3
As mentioned by Linum Labs, that approach can be used for solidity v 0.7 and higher. If you want to use an older version,
From docs:
\uNNNN (Unicode escape)
You will need to convert Unicode character to escape sequence, For example:
✕ray Ýour ℤen
will be
\u2715ray \u00ddour \u2124en
And Important NOTE from docs:
Any unicode line terminator which is not a ...
3
Welcome!
Just as a quick note, you mention "smart contracts" in the question, but give code that looks like Solidity, and also have a Solidity tag in your question, so I assume that the question's focus is Solidity. Different languages may handle Unicode differently, so the answer can change from language to language.
Solidity (v0.7 and higher)
(...
2
For instance: 1️⃣is has three characters: The digit one: 1, variation selector, a Combining Enclosing Keycap.
It does have 3 characters, but they take 7 bytes.
But in Solidity, 1️⃣ is counted as 7.
You are treating the text as bytes, so it's correctly returning 7.
One option would be to count the number of bytes - instead of characters - in JS on your ...
2
You can use web3.eth.abi.encodeParameters:
const web3 = new Web3;
web3.eth.abi.encodeParameters(
['address', 'uint256[]'],
['0x6b175474e89094c44da98b954eedeac495271d0f', [1, 2, 3]]
);
Results in:
...
2
The more comprehensive explanation can be found here: What are Artifacts
In short, truffle artifact is a JSON bundle that contains a lot of useful information related to a contract like the ABI, the contract bytecode, the deployment details, compiler version, etc...
2
In version 0.7.0, the alias now (for block.timestamp) was removed.
2
You can have multiple functions with the same name, as long as their signature is not the same. The parameters are also part of the signature, so the function signature of those two functions is different. So the functions do not get mixed up in any way. Whenever you call a contract function, you have to provide the parameters as well. The executed function ...
2
You can use the CHAINID opcode to get the current chain ID. AFAIK, Solidity does not have a built-in function for this, but you can use inline assembly to get the chain ID in a Solidity contract, e.g.:
function getChainId() private view returns (uint256 chainId) {
assembly {
chainId := chainid()
}
}
Then you can check if the chain ID is 1 for ...
1
_lp is the Pancake liquidity provider token to stake in the farm pool and wbnb is a wrapped BNB token on Binance Smart Chain.
1
There is an explanation in the original Github ERC721 thread about keeping the "unsafe" transfer function (comment from Dieter Shirley, alias "dete", one of the authors of EIP-721) :
Upon further reflection and discussion with @flockonus, we are
proposing to keep a straightforward (and therefore "unsafe")
transfer() method. (i....
1
mappings cannot be copied around through assignment either in storage or memory and can only be referenced. A work around is the following snippet.
struct Dividend {
mapping(address => bool) claimed;
uint256 pool;
}
Dividend[] public dividends;
function createDividends() public {
uint256 idx = dividends.length;
dividends.push();
...
1
If this needs to be encoded into your smart contract logic you will likely need to actually keep the state in the smart contract storage.
Otherwise if this is just for analytics you can use the graph to aggregate that information over time. Here's an example of how uniswap makes their analytics page using the graph: https://github.com/Uniswap/uniswap-v2-...
1
You should not adjust the scale like this. msg.value is already scaled properly.
tokens = msg.value * 10;
This is useless. A balances mapping is usually used to track liabilities owed by the contract to other users. But you forward the funds immediately so you have no need for this.
balances[msg.sender] = safeAdd(balances[msg.sender], tokens);
It's not ...
1
I am not aware of a solution for this.
Etherscan will recompile the contract that you provide with the parameters that you provide. If the result matched the deployed bytecode, it will mark the contract as verified.
The thing is that even changing the number of optimization runs or the compiler version can change the resulting bytecode. In other words, you ...
1
By default, a contract without a payable function can't receive Ether. However, there are some exceptions, or tricks, on how it's possible: https://ethereum.stackexchange.com/a/63988/31933
But for normal usage, you need a receive payable (https://docs.soliditylang.org/en/v0.8.0/contracts.html#receive-ether-function) function in the contract. So the minimum ...
1
This answer is about nightly builds in general and not specific to solidity.
A nightly build, in general, is a build of a version, that is not finished yet.
So there might be more bugs or missing features.
It is basically a build of the current work in progress.
It is called nightly build because it is common to automatically build them from the current ...
1
You error is not related to nightly builds. One of your files (SafeMath.sol) requires a compiler version (pragma solidity ^0.4.23) lower than the one you selected (0.8.3).
1
This is a very important topic, and it's been pointed out that not enough attention is given to it.
Ultimately, immutability is a bit of a spectrum. If somehow every last device storing the Bitcoin and Ethereum networks would be destroyed, the networks would be lost. Fortunately, that is improbable enough to not worry about. Similarly, even IPFS is not as ...
1
const TodoList = artifacts.require("TodoList"); // Enter your Contract Name not File name
module.exports = function(deployer) {
deployer.deploy(TodoList);
};
1
NFTs are auctioned in various ways on various platforms. An auctions could theoretically be completely centralized - an owner says they're taking bids until a certain time, potentially even off-chain, and at the end of the time, the bidder informs the winner they have won, accepts their payment, and sends the NFT. There wouldn't be much you could do with a ...
1
Ethereum doesn't do that.
You need a price source which could be on-chain or off-chain. Off-chain would be an exchange or other service, e.g CoinMarketCap and that would be an API. On-chain could be a price Oracle or liquidity pool, e.g. ChainLink or Uniswap. There are many in both cases.
Hope it helps.
1
you are missing ; in import
import "@openzeppelin/contracts/utils/Counters.sol"
should be :
import "@openzeppelin/contracts/utils/Counters.sol";
Moreover, use ^0.8.0 because openzepplin contracts are compiled in it and use @openzeppelin/contracts 3.0 (npm) as _setTokenURI is not available in v4 (replaced by other function)
1
The problem was because when using UniswapV2Factory, only the precompiled UniswapV2Factory contract in the build directories from @uniswap should be deployed as stated in docs https://uniswap.org/docs/v2/smart-contract-integration/quick-start/. So, even if I commented out something on my UniswapV2Pair contract, it had no effect, because UniswapV2Factory uses ...
1
When you hit "Compile ww1.sol", the remix will compile all contracts inside that solidity file.
After compiling the ww1.sol, If you change Context (Context.sol) to NiftToken (ww1.sol) (NOTE: don't click compile again after changing to NiftToken) and then click on compilation details then you will see the ABI of NiftToken
Example:
For Q2,
You don't ...
1
It appears the public Vyper server is down. This video (https://www.youtube.com/watch?v=5M5p6SnW-Og) explains how to get your local server running. You could follow his instructions, or if you have Mac, you could try what I did:
$ brew install gmp leveldb
Next I activated a Python 3.9 virtualenv and then
$ python3.9 -m pip install vyper
Then I could ...
1
After doing some research I finally have the answers to the questions.
1. What is the abi object inside the contract and what does it do? Is it the same as the one you get when you compile the contract?
According to the solidity docs:
The Contract Application Binary Interface (ABI) is the standard way to
interact with contracts in the Ethereum ecosystem, ...
1
From Solidity v0.8.0 Breaking Changes https://docs.soliditylang.org/en/v0.8.0/080-breaking-changes.html
ABI coder v2 is activated by default.
So it is not experimental, but standard feature since solc v0.8.0
1
On the left of the Remix workspace is the "Icon Panel."https://remix-ide.readthedocs.io/en/latest/layout.html
At the top of that is the Remix logo icon that looks like a head with headphones.
Click the Remix logo icon to open the "Home Page."
On the Home page, on the left is a "File" section.
In the File section is a link to &...
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