Questions tagged [inheritance]
Inheritance in this stackexchange refers to parent child contract relationship where the child contract is considered to be a type of the parent contract and hence implement the parent contract functions. This is same like inheritance in OOP in generic programming except for the fact that in this community its used in a contract oriented programming domain.
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What is the purpose of the import statement in Solidity?
Could someone explain to me what the pupose of the import statement is, in Solidity? Is it the similar to inheriting from another contract where you have access to the state variables and function of ...
- 43
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2
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65
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Trying to create a soulbound token. Keep getting two errors
I'm trying to create a soulbound (non-transferable NFT) token on Solidity. Here is my code so far.
// SPDX-License-Identifier: MIT
pragma solidity >=0.4.17 <0.9.0;
import "@openzeppelin/...
- 11
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0
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10
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Who is the msg.sender in the context when calling the "super.{....}" contract method on the inherited parent contract?
The child contract's method is: (1)
function redeem(
uint256 shares,
address receiver,
address owner
) public override andSync returns (uint256 assets) {
return ...
- 264
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How to cache the result of an inherited function before overriding it
contract A {
function getUINT() public virtual view returns (uint) {
return 100000;
}
}
contract B is A {
uint trycache;
uint public trycache2 = getUINT(); // still 200000
...
- 79
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12
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Need help with debugging Error: Definition of base has to precede definition of derived contract
I'm working on a social account recovery feature for smart accounts (ERC-4337) on top of Thirdweb's smart account contract.
Link to the codebase
I'm getting the error Base has to precede definition of ...
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0
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22
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Free functions cannot have function visibility
I am developing my Dapp and as I am trying to compile and test my contract I keep getting an error saying that free functions cannot have visibility and I am very frustrated and confused as to what is ...
- 73
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Re declaration question - Inheritance & overriding
I need help clearing somethings up when it comes down to redeclaration and implementation of inherited functions. I have an example below. I am building an nft erc1155 marketplace and inherited the ...
- 73
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How do i directly write in my ERC721 parent's private mapping?
MyContract is ERC721
I want to adapt the _update function to a specific usecase.
In order to keep its core functionality, the adapted function needs to write into _owners, _balances and ...
- 47
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1
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39
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question about interfaces and inheritance
I am building my own application for an erc1155 dapp but have some questions about interfaces and inheritance. How do you re-declare functionality that you inherit from another contract? Also, how do ...
- 73
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How to inherite modifier into multiple contracts ? Best practice?
I have a project with severals contracts.
To put some security, I've created a "onlyContract" modifier on a Roles contract so some functions in diferents contracts can only be called if the ...
- 21
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Inheriting a contract to match state layout in a delegatecall
What is the best way to manage the state layout of a contract will exclusively be used via a delegatecall?
Let's say that there is a Parent contract that uses delegatecall on a Child contract. Within ...
- 11
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Can you change an overridden function's visibility/mutability?
Say I have a parent and a child contract, in the child I don't want to use one of the parent's functions, so I changed the logic to just revert if it is ever called.
Now the terminal output shows me ...
- 1,408
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1
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54
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Solidity Inheritance - Changing state variable content
I am new to Solidity and when I tried this code below and try to change the value from the child contract, it did not work.
// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.18;
contract ...
- 13
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1
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How can I inheritance an interface without abstract?
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.19;
import "./IERC20.sol";
abstract contract Lock is IERC20 {
string name;
string symbol;
uint8 decimals;
...
- 3
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1
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24
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Is it possible to have access to an internal function of a smart contract already deployed?
I have a smart contract A which inheritates B :
contract A is B
In A, there is a function "test() onlyowner" calling B.otherFunction().
In B, otherFunction is just internal. Dont have the ...
- 3
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1
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Why do some developers make their base contract inherit its Interface?
Some protocols and developers inherit the contract's Interface inside of the base contract and then have the interface contain the actual NatSpec, is this simply for human readability/code ...
- 1,408
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34
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How do modifiers effect function signatures?
I want to change a function that my contract inherits to have a modifier, but are you allowed to add modifiers to overridden functions that didn't previously have a one?
- 1,408
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10
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Vyper: How to test internal helper functions?
I'm writing a Roulette contract as a learning activity in Vyper. My contract seems to be working through manual testing, and now I'm starting to write unit tests.
I have an internal helper function ...
- 151
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1
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13
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I'm getting error every time I'm calling withdraw function from treasury contract?
//Treasury.sol
SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;
import "./Lending.sol";
contract Treasury is Lending{
Lending lending = new Lending();
bool internal ...
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0
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22
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Function Visibility specifiers during inheritance
when am overriding a function in solidity must my child function have the same visibility as the parent function? can the parent function be public and the child function be internal
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10
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Inheritance, leaving crypto to a child, drip by drip
How would be best to lock,up some eth (or other crypto, BTC?) for example, for my sons future ? Ie so that his wallet receives a certain percentage of the contents of my account over a certain period ...
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2
answers
56
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Constructor Inheritance: : Wrong argument count for constructor call
In the following, why is the constructor of C not inherited by CExt so that it can be used by another extending contract CExtChild?
contract C {
uint id;
constructor(uint _id) {
id = ...
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17
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how to use onlyGovernance modifier?
I want to use onlyGovernance modifier in my contracts. I have a governance contract but I want to use this modifier that is not a governance contract. I want to use it so I can restrict some of my ...
- 253
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86
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For function overriding, why can visibility be made less restrictive, but mutability only more restrictive?
From the solidity docs:
Function Overriding
Base functions can be overridden by inheriting contracts to change
their behavior if they are marked as virtual. The overriding function
must then use the ...
- 323
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1
answer
31
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Overriding in multiple inheritance
If I have the following contracts:
contract A {
function _delegate() internal virtual {
//some code
}
}
contract B is A {
//some code not including _delegate()
}
contract C is B {
...
- 711
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votes
1
answer
59
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Difference between storing an address versus a contract instance?
What is the difference between storing an address of a contract and using a interface to interact with it, versus storing the type of the contract itself (i.e. IPriceFeed v. PriceFeed) within the ...
- 136
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1
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385
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How to call a function that is inherited from another contract using Hardhat?
I have deployed a smart contract that inherits ERC721EnumerableUpgradeable which inherits ERC721Upgradeable.
When I deploy using Remix, for example, I see the function safeTransferFrom, which is a ...
- 683
1
vote
2
answers
119
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Contract storing array returning addresses
Below is the contract which imports another contract
pragma solidity ^0.8.7;
import "./SimpleStorage.sol";
contract StorageFactory {
SimpleStorage[] public simpleStorageArray;
...
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1
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35
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Is it possible to write an inheritable extension contract that supports multiple parent implementations?
I'm writing an extension to be used with a ERC721 contract. Is it possible to call a function like balanceOf() which should be defined in any implementation of ERC721, without having to define the ...
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2
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537
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Upgradable contract with new inheritance
I've deployed a smart contract that inherits a few other contracts, simply:
contract A is B,C,D {}
Now, i have no issue with upgrades when it comes to upgrading A,B,C or D. My question is, what will ...
- 35
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1
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99
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Inheritance issue using virtual and override (probably): Member not found
I'm trying to work through a course that is covering virtual and override and seem to be getting an error due to inheritance. Below is the code:
//SPDX-License-Identifier: GPL-3.0
pragma solidity >...
1
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3
answers
613
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Why do we need interfaces in solidity?
Let's say contractA has a special function. And made an interface that contains the special function without implementation. To use the function in the other contractB, we can use the interface but ...
- 375
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1
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27
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How Linearization is possible in first block of code but not in the second block of code?
First block of code
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/ERC721.sol";
...
- 21
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0
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64
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`transferOwnership` is not a function
I am following the challenges from the speedrunEthereum and right now I am stuck on challenge 2 and not getting why the transferOwnership is not a function since I am also inheriting the Ownable from ...
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1
answer
57
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modifiers overriding simple question with inheritance
just wanting to be sure of this. If I have a contract that inherits from another contract and overrides a function of that contract with NonReentrant modifier on it. Will that NonReentrant modifier ...
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1
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105
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What is the practical purpose of interface contracts?
I wanted to make sure I understood the purpose of interface contracts. I understand that they are contracts with unimplemented functions, but wanted to make sure I understood all the ways programmers ...
- 105
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1
answer
93
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Multiple inheritance in Solidity
I have a contract C that is Ownable so I can use ownerOnly on its admin functions.
Recently, I added some functionality that I'm going to start using in other projects. I refactored the functionality ...
1
vote
1
answer
135
views
Does the compiler ignore internal functions that are never called?
On inheriting a contract that contains some internal functions that are never used in the child contract. eg.
contract Parent {
function _someInternalFunction() internal{
}
}
contract Child ...
- 11
4
votes
1
answer
555
views
How does Solidity implement C3 linearization?
The solidity documentation does not offer a lot of insights into their implementation of the C3 linearization to resolve methods in a multiple inheritance scenario. There it states that
You have to ...
- 297
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1
answer
34
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Create contract with contract
I want to create a contract that can create contract itself
I find something like this
pragma solidity ^0.5.0;
contract DaughterContract {
string public name;
uint public age;
constructor(
...
- 33
4
votes
1
answer
668
views
Interface overriding giving error. Overriding public state variable return types differ [duplicate]
I am trying to import interface in it's contract and overriding function. But 1 mapping is giving error.
Error:
Overriding public state variable return types differ.
Interface:
interface ...
- 1,108
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2
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457
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What is the preferred Inheritance for ERC20 token and why?
I tried to deploy both ERC20 contracts with burn functionality over the remix and both seems to work fine, I am confused if one way should be preferred over the other. Since, openzeppelin contract ...
- 201
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281
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Solidity: calling a imported contract's function without inheritance, Calling a imported contract interface and passing its implemented contract add
This is the error I'm getting, I'm trying to implement ERC20's _transfer function without inheritance, calling its Interface IERC20 and passing the ERC20 deployed contracts address and then calling ...
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2
answers
809
views
How to import Openzep ERC20: Identifier not found
Can I get someone's perspective on why I'm unable to find the ERC20 contract I've npm install @openzeppelin/contracts.
After import "@openzeppelin/contracts/token/ERC20/IERC20.sol"; I get a ...
- 117
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3
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869
views
Why is my Open Zeppelin import in Remix throwing an error?
I am importing ERC20 from OpenZeppelin but it's not working!
Here is the code:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "https://github.com/OpenZeppelin/...
- 1
1
vote
1
answer
581
views
Is there a way to override or skip calling a parent's constructor?
Is there a way to override or skip calling a parent's constructor? For example, I have the following:
contract Ape {
constructor() {
// Initialise some stuff in Ape constructor
}
}
contract ...
- 447
0
votes
2
answers
39
views
How can I inherit contact on github?
there is a contract on github. I need to inherit it/ So how can I do it? Using import isn't available how I unnderstand..
https://github.com/Uniswap/v2-periphery/blob/master/contracts/interfaces/...
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In Contract D, why does calling function bar first call C, then B, and finally A?
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.10;
/* Inheritance tree
A
/ \
B C
\ /
D
*/
contract A {
// This is called an event. You can emit events from your function
// ...
1
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2
answers
555
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Why does OpenZeppelin import interfaces to its own contracts?
I've noticed that all OpenZeppelin's token contracts import their interfaces into them.
Why does OpenZeppelin import and inherit its own contract interface to the contract?
Does importing a contract'...
- 514
0
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1
answer
58
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Array type of an array or contracts?
If I have a contract named LockedOffer, and in another contract that inherits from LockedOffer I declare an array LockedOffer[] public offers, what type is the array? I'm assuming it's an address ...
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