Questions tagged [design-patterns]
A design pattern is a general reusable solution to a commonly occurring problem in software design. Use this tag for questions when you're having problems with the implementation of design-patterns. Please don't use this tag on questions about text pattern matching. When using this tag on implementation heavy questions - tag the code language the implementation is written in.
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Can the `totalSupply` of a token be different than the sum of all account balances?
If I'm building a rebase token that has a difference of 1 wei sometimes (pre/post rebase) between the totalSupply and the sum of the balances of all holders, does that pose an attack risk within the ...
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Reentrancy Guard and CEI
Could you please explain, is there a need to use a ReentrancyGuard modifier if the contract follows the CEI(Check Effect Interactions) pattern? If yes, could you bring an example, where the contract ...
- 13
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0
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Solidity design pattern drawbacks
I was ask by a friend to give feedback on his solidity project. I came over a general design pattern issue, which is not good from an object oriented point of view. I try to outline the projects ...
- 71
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How do you use the Diamond Pattern for escrow upgrades?
I am creating a contract with the diamond pattern so I can evolve and add new features to my contract.
Contract facets:
Contract A: an ERC721 that takes care of minting its own NFTs
Contract B: ...
3
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0
answers
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`delegatecall` in batch call stops working as expected when changing the code slightly
I have the following function for batching multiple calls, which returns the result (success or not) and the return data for each corresponding call.
function callBatch(bytes[] calldata calls) public ...
- 131
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1
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Is it possible to batch-call the function multiple times so it's executed asynchronously and make profit from that?
If an attacker batch-calls the vulnerable contract's function in a re-entrancy attack attempt, would the transaction with a CEI pattern violation be fully executed before the other transactions are ...
- 1,179
2
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2
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65
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Solidity Proxy: why using initialiser instead of a constructor?
Why proxies can't read from the constructor?
- 225
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1
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What is the Web3 approach to storing secret tokens (for example, when need to store the local salt for commit/reveal pattern)?
What is the Web3 approach to storing secret tokens (for example, when need to store the local salt for commit/reveal pattern)?
I'm currently using local storage.
For example in Web2 a back-end layer ...
- 1,179
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0
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Complex factory optimization
After two and a half years of developing smart contracts on a non-EVM blockchain (Tezos), I started working on a few solidity projects, and I'm trying to understand some things.
I built a factory ...
- 36
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1
answer
686
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How to make UUPS upgradeable contracts modular
I have the following contract:
import { UUPSUpgradeable } from "@openzeppelin-upgradeable/proxy/utils/UUPSUpgradeable.sol";
import { OwnableUpgradeable } from "@openzeppelin-upgradeable/...
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1
answer
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Cloning ERC20/ERC721
I'm using a Clone Factory pattern to create new instances cheaper. I realized that every field, preset or set in constructor, has default value. Let's assume that I have this contract:
contract ...
- 111
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1
answer
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Is there a reason a function is made public and then called internally in Solidity?
I have come across a popular smart contract in the OpenZeppelin library that manages access control of a contract.
This is the library:
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/...
- 111
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vote
0
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Storage design for a social network
I want to create a social network app using Solidity, but I am having a hard time thinking of the storage design. Using this link:
Are there well-solved and simple storage patterns for Solidity? as a ...
- 111
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1
answer
1k
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Using ABI's in Proxy contract pattern
I am planning to implement a Proxy pattern for my smart-contracts. And I want to make sure I understood it's use-case right.
In short: User only needs to know about Proxy contract address, and by ...
- 2,292
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Getting data from contract instance created via Factory pattern with Hardhat
I had two contracts AuctionFactory and Auction contracts.
contract AuctionFactory is IAuctionFactory {
using Counters for Counters.Counter;
Counters.Counter private auctionIds;
uint256 ...
1
vote
1
answer
316
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Solidity private/internal function call from external function
what the purpose of that way to restrict access to function call?
function updateQuorumNumerator(uint256 newQuorumNumerator) external virtual onlyGovernance {
_updateQuorumNumerator(...
- 75
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Is there a design pattern in order to protect private keys in a Multi SigWallet?
I've developed a MultiSig Wallet for my company. For timing reason i've used as "code base" the Ethereum Multi Sig Smart Contract by BitGo (here the link of the repository: https://github....
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Does it cost more gas to call a function more than once in another function?
Does it cost more gas to call a function more than once in another function?
For example:
function getValue() public returns(uint){
return 5;
}
function getOtherValue() public returns(uint){
...
- 1,843
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1
answer
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How to handle memberships of multiple users of a scheme
I am very, very new to blockchain development and even newer to Ethereum. Have done / am doing some online course though...
Anyway, how would one handle the situation where you might have a scheme ...
- 101
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1
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splitting contract in data and application contract
I made 2 contracts in 2 different solidity files. Lets for simplicity assume the contracts are called A and B. A contains data and some simple function calls, B contains more complex function calls. ...
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Can I make a delegatecall to a Solidity contract that is compiled with a higher compiler version?
Lets say that I have the contracts A and B.
A needs to make a delegatecall to B.
A is (for some reason) compiled with a compiler version that is lower than B's compiler version.
Can I safely assume ...
- 828
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Graph traversals on Ethereum, at scale
I read the Efficient Solidity storage pattern for a directional weighted graph thread, but that deals with storing graphs. I'm interested in techniques for how to traverse graphs in Solidity, at scale....
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Ho can a server act for third party?
I will try to explain my idea.
Our server receive data to save from different servers, we call it S1, S2 and S3.
Our server uses a node script with web3.js to call function over a contract. Actually ...
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Which Pattern to follow to create contract?
I have an ad campaign and I want to store data(like campId, number of impressions, start date, end date etc.) of each campaign on blockchain. Also, whenever I will pass campId, I should be able to ...
- 75
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1
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How do you pause a Proxy-Logic pattern?
Suppose we have a Proxy contract that forwards to call to a Logic contract by using delegatecall.
If we pause the Proxy, users will still be able to directly interact with the Logic contract. While ...
- 169
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Split State Storage Contract
This is a follow-up question of Split Contract Design Pitfall
Background: I have split my logic into two contracts A and B. A keeps the state and not ETH. All state change functions are only allowed ...
- 361
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2
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Reason for check of msg.value > 0
I came across published smart contracts (like this one from ConsensSys) that check whether msg.value is strictly larger than zero in their payable functions.
After wondering whether msg.value can be ...
- 518
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2
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Self Destruct Design pattern - Loss of funds issue
I was exploring on self destruct design pattern for a time bound smart contract. So my contract should not accept any further state change after a certain given time period.
While working on that I ...
- 340
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1
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What is the Withdrawal Pattern?
I am reading this article : https://medium.com/@jgm.orinoco/why-use-the-withdrawal-pattern-d5255921ca2a
It seems interesting. Could anyone explain the idea of the Withdrawal pattern in a simple way ?
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Design pattern Checks-Effects-Interactions Pattern
I was workig on design pattern Checks-Effects-Interactions Pattern and found the below link which has a similar question but in the direction which I am looking at ..
Checks-Effects-Interactions ...
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1
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Issue in type conversion : Explicit type conversion not allowed from unit256 to bytes1
I am trying to convert the unit to string using the method. I have the "TypeError" in the line. Please check the screen shot below for the error message.
function uint2str(uint i) internal pure ...
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1
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Circular reference error in factory contract pattern
I've used the factory model before, but I've never encountered a circular reference error, and I'm having trouble seeing how this could be a circular reference when I'm creating a brand new ...
- 247
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Solidity/Remix Error: The constructor should be payable if you send value enum change state
I'm using this (State Machine) design pattern in solidity and having an error when changing the state after executing the first function. Any hint? Thank you!
Error: revert The transaction has been ...
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Design pattern for game development
I am developing a game which currently uses a GameFactory contract to create instances of a Game contract.
The Factory pattern would allow any number of players to play their own single player game ...
- 361
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2
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What is the proper pattern to use a temporary variable and ensure it gets stored?
A contract has a state variable, which is complex. For the example, lets say it is a mapping of structs. Inside a method, I want to access that and store the changes. Like so:
contract FooManager {
...
- 217
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1
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Production Fork of Ethereum
everyone!
I have a project, where I surely need to implement transparency of all the actions doing in the network. Let's say I want to create public asset tracking. So everybody who posts an asset in ...
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How can contracts share a whitelist?
I have a token, let's call it TokenA, that inherits from Open Zeppelin Whitelist.sol. TokenB and TokenC both inherit from TokenA and they each have some additional functions.
I want all three Tokens ...
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2
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How to identify submitted transaction to network?
I am developing an eCommerce application that has on-chain and off-chain components. The off-chain components focus on the compute and storage intensive operation while on-chain smartcontract ensure ...
- 447
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0
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What is a common pattern to work with a large number of complex Things: make a Thing a contract, or a struct in a mapping?
In order to build a somewhat complex Dapp, I need to manage "Contributions". To do this, I roughly see two patterns:
A Factory-pattern, in which each Contribution is it's own Contract/Instance.
A ...
- 217
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0
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Listen for Solidity Event With X Number of Confirmations
I presume Solidity events are fired the moment the block that includes its transaction is mined -- please correct me if I'm wrong.
I need to sync the transaction status locally but wish to only save ...
- 361
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Why lot of Smart Contract implementations are using a single instance to hold all accounts?
I found a lot of example of tokens (like ERC20) using this pattern:
contract MyCoin {
mapping (address => uint) balanceOf;
...
}
Those contracts are deployed once, the "balanceOf" ...
- 15
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Oraclize __callback function with unbounded gas usage
I am making a lottery contract and using Oraclize to select a winning number.
Here is what I have now:
The owner calls a finalize() function, which disallows new entries, and makes a call to ...
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Withdrawal pattern in fallback function
I need to implement withdrawal pattern for my smart contract. I wanted to make it possible to interact with contract for the people, who use smartphones and tables, just by sending some amounts of ...
- 191
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Where does Ethereum Dapps go in known design paterns
I am doing a Dapp for a school project and I am supposed to choose a design pattern to work with.
I want to know the possibilities for design patterns concerning the ethereum dapps, or if they have ...
- 3,060
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Should UIs handle 4Byte function selector collisions?
With 4 bytes collisions are possible.
But they are not very likely. Currently in the 6,846 entries in the 4Byte.directory there are no collisions.
Still they are possible. Now I wonder if UIs should ...
- 1,183
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Are there any downsides to if...else logic versus rejecting in a function
Pretty much all examples of contract functions I see use the require(...) pattern. If the initial condition is not as expected, an error is thrown and the transaction is reverted.
I don't like this ...
- 1,147
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0
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Build blockchain application that has some off-chain functionalities
I am learning about blockchain and I have a general question. Let's say that I want to build my custom blockchain based on Ethereum. My implementation has many nodes and few of them are chosen ...
- 405
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2
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279
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Web wallet best practices
I'm putting together an ether/erc20 token wallet in a chrome extension but would like to follow best practices with regards to private key security.
I'm using localstorage to handle login and its ...
- 151
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103
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Modeling language for Block-Chain-Oriented Systems
Any ideas about how do i use graphic models for representations. Should i follow UML diagrams style?
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598
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Solidity local validation call before sending state changing transaction
I have an use-case where the user should be able to change a contract's state only when the inputs pass a validation check. However the validations are expensive to perform and can be done locally ...
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