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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Calling super class external functions

Is there a way in Solidity to call super class external functions? Normally with inherited contracts, when overriding inherited functions you can also call the original function logic with super....
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Abstract contract not inheriting constructor from parent abstract contract

I'm using solidity 0.7.1 and I seem to be running into issues while inheriting from an abstract contract. Specifically with the open zeppelin library, now I'm not creating an issue there because their ...
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1answer
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Multiple Inheritance - Inheritance Graph Impossible

I'm trying to build a contract based on the ERC1404 standard outlined here: https://github.com/simple-restricted-token/simple-restricted-token The contracts allow you to add restrictions on top of ...
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Why Can't I Call This Parent Function in Solidity?

Parent function in ERC1155: function uri(uint256) external virtual view override returns (string memory) { return _uri; } Attempted overriding function in my child contract: ...
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1answer
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A contract inherit from a token contract

I have a token contract(ERC20) A, then another contract B inherited from A (B is A). A contract C imported B. questions are: if I deployed B alone, is the address of this contract B represent the ...
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I written an ERC20 token contract, now I have to use my token in another contract for transaction amount. How? [closed]

Taking help of openzepplin, in making ERC20 token , I now have to use this token in multiple contracts for various use. So, how do I code my ERC20 token into other contracts, so that at time of amount ...
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1answer
16 views

Call method of another contract from one contract in upgradable smartcontract

I have two contracts Vase and Box contract Vase { uint256 public vase1; event VaseValueChanged(uint256 newValue); function createVase(uint256 newValue) public { vase1 = newValue; ...
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0answers
32 views

Polymorphism in Solidity

I understand that Solidity supports contract polymorphism, but what pattern would one use to create abstract data types for use in derived contracts? Motivating example: Say I have an abstract Storage ...
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1answer
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Read and write private variable from child contract

I have a contract MyContract is ERC721. MyContract needs to concatenate a string with an existing token URI using this function: string(abi.encodePacked(_tokenURIs[_tokenId], _URI)); Problem is all ...
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Underhanded Solidity: Exploiting multiple inheritance

In an article by Steve Marx (on Medium.com), the author argues against using inheritance in solidity not only because of harder readability of a Smart Contract, but also because it can be exploited in ...
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1answer
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Multiple inheritance name collisions

I am trying to understand how multiple inheritance in Solidity works with this snippet of code. where contract C inherits from A,B with each having function foo. pragma solidity ^0.6.0; contract A {...
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2answers
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Trying to reference function from parent contract - Member “xxx” not found or not visible after argument-dependent lookup in address

I am trying to make a parent contract which deploys a child-contract for each unique caller (which does not inherit from parent contract, but calls one of the parent's functions). I have looked up ...
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1answer
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Can a contract be inherited?

Just a random thought and a question. Can a smart contract written in solidity be inherited and if so, How?
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1answer
283 views

Value of msg.sender in call to inherited external function

I found this in the official solidity docs. The values of all members of msg, including msg.sender and msg.value can change for every external function call. This includes calls to library ...
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2answers
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How to disable a function from a parent contract?

Say I have this contract: contract Foo { uint256 public foo; function setFoo(uint256 _foo) public { foo = _foo; } function setFooToZero() public { foo = 0; } } ...
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1answer
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Cannot call functions from another deployed contract that inherits yet another contract

I am just trying this using Remix editor. I am able to call functions from another deployed contract(plain as simple) but when that another deployed contract inherits yet another contract, Now the ...
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Trustless contract upgrades using inheritance

I've been struggling to find a solution to the problem of upgradeability that maximizes trustlessness while also putting minimal burden on users. I really wanted to use signed messages to validate ...
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1answer
45 views

openzeppelin mint sequence

// openzeppelin v5 contract ERC721Full is ERC721, ERC721Enumerable, ERC721Metadata { constructor (string memory name, string memory symbol) public ERC721Metadata(name, symbol) { // solhint-...
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1answer
52 views

Multiple Inheritance at particular contract address

I'm attempting to have 4 different contracts sharing the same data fields. The reasoning behind having 4 instead of 1, is that the different functionality can be broken down so that it is cleaner, ...
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1answer
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linking the CoreContract and the ERC20 token contract

What is the standard way of making the link between our CoreContract and the ERC20Token contract used by the Core Contract? Are people used to use inheritance like: MyCoreContract is MyERC20Contract { ...
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1answer
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How to restrict call to inherited public function

I'm using OpenZeppelin library for my project and I need to override some functions for business logic. But my concern is with given example, // contract from library contract A { function ...
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2answers
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How can I check if a specific contract's address inherits from a interface or contract?

I have a special contract with few extra functions. In the transfer wei function I want to send it to the special method or if receiver doesn't have it (because is a wallet or doesn't inherit from my ...
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1answer
37 views

Import and polymorphism is one contract or more?

If I have this contract: contract HelloWorld{ ... } and this one import "./HelloWorld.sol"; contract HelloUniverse is HelloWorld{ ... } and I deploy it, will it create 2 different contract and 2 ...
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1answer
115 views

Interface overriding

I have two contracts. One of them inherits another. Inside the parent contract I have the interface interface Token { function transfer(address to, uint256 value) external returns (bool); } I ...
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1answer
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Who is “from” in case of inheritance in solidity?

I have the following code: // Test.sol pragma solidity ^0.5.2; import "./TestBase.sol"; contract Test is TestBase{ string[] name ; constructor() public payable { name.push("sheep"); ...
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1answer
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Import a contract hosted on a testnet from it's address

I have a smart contract that imports another, and I'm wondering how to deploy them to a testnet. Right now, one contract imports the other locally; import "./firstContract.sol" contract ...
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2answers
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Inheritence in Solidity

I want to implement my contract in much better way and want to use the inheritence. I wrote the code and i face one problem that i want to access the mapping variable of Contract A in the Contract B. ...
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1answer
188 views

question regarding linearization of inheritance

If I have the following inheritance: pragma solidity ^0.4.24; interface A { function foo(uint256 _x) external pure returns(uint256); } contract B1 is A { function foo(uint256 _x) public ...
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1answer
119 views

Solidity inheritance can't read parent's value correctly

I found a strange error in my contract and tried to resolve it, but it's so unreasonable. contract parentContract { uint num = 1; function setNum(uint _n) public returns(uint) { num ...
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1answer
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In Solidity, how does the slot assignation work for storage variables when there's inheritance?

In a simple solidity contract, without inheritance, storage variables get assigned sequentially starting from slot 0. But in case of inheritance, the inherited variables appear before or afterwards?
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1answer
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Solidity Syntax question

What happens if a function is being passed before { into another function? Like DetailedERC20(_name, _symbol, TOKEN_DECIMALS) in this example: function MyToken(Registry _registry, string _name, ...
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1answer
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Why is it that my first original contract containing the setters and gettters are not showing up when I hit deploy?

pragma solidity ^0.4.24; contract Bank{ uint private value; constructor(uint amount) public{ value = amount; } function deposit(uint amount) public{ value += amount; ...
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2answers
33 views

Is it possible to have an optional property or method in an interface?

I currently can't deploy any contract which doesn't adhere 100% to the specified interface(s). Is there a way to mark some properties or methods as optional and, if not, is this a planned feature?
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1answer
68 views

Contract Using An Interface Is Not Compiling

I am learning Solidity and I am using Remix to experiment and enhance my learning. I am currently trying to create a simple contract that uses an Interface. pragma solidity ^0.4.19; contract ...
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1answer
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on a way of copying code that involves “super” keyword for supporting inheritance

I wonder the exact mechanism of copying code that involves "super" keyword for supporting inheritance in Solidity. Below is an example code that elaborates my question. contract C { function ...
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1answer
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Contract Inheritence

Let's suppose we created two contracts: Contract A and Contract B. Contract A is inherit by Zeppelin's standard token ERC20 where as Contract B is inherit by contract A. Will contract B be ...
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2answers
239 views

Is library use inherited?

When a base class uses a library, do derived classes also use the same library? For example: contract A { using SafeMath for uint256; ... } contract B is A { //is code here using ...
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1answer
20 views

Do over-ridden functions affect dependent parent functions?

Imagine a ParentContract with functions a() and b(), where b() calls a() contract ParentContract{ function a() {...} function b() { a() } } Now, I have a Child contract that ...
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1answer
67 views

Diamond inheritence problem [duplicate]

interface I { } contract A is I { } contract B is A { } contract C is A { } contract D is B, C { } What would happen in this situation? How is this kind of diamond inheritance resolved in ...
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1answer
167 views

Should Solidity interfaces always specify return types?

I've seen interfaces in which the function definitions specify a return type, ie: (from openZepplin's IERC721.sol) function balanceOf(address owner) public view returns (uint256 balance); and ...
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1answer
48 views

Solidity inheritance

Do contracts have to implement the methods they inherit from interfaces, likewise, do they have to implement methods from abstract contracts?
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3answers
275 views

Composition Over Inheritance - Gas Efficiency

In OOP languages, composition over inheritance is a well-known best practice. Solidity is an OOP language too but there is also the gas efficiency issue. Question is, in Solidity, how do composition ...
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1answer
241 views

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 ...
2
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1answer
280 views

msg.sender is Null in Base Constructor

When I create the child class object and try to access value of msg.sender from parent class it always comes 0. Can anyone please help me in this? Below is the sample code: contract Test1 is Test2 { ...
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1answer
221 views

Call parent class modifier possible?

I want to do the following: contract Base { bool public active; modifier canSetMetadata() { require(active == false); _; } } contract BaseWithMetadataControl is Base { ...
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1answer
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What order is code copied for inheritance?

The Solidity documentation says it supports inheritance by copying code, but is unclear about where the code is copied to. I am building a genesis block for a Quorum-based chain, starting from the ...
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1answer
116 views

A Solidity Linearization Puzzle

I was playing in remix just to concretize my understanding of Solidity linearization, and got a result I didn't expect and can't rationalize. Why does AC_BA.go() return 3? (Please scroll to the ...
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2answers
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Gas estimation failed in Remix

Can't really use the transfer function as it is written. It assumes the owner uses it. So made a new function for the "minting" function for the faucet to use. Not sure why the compiler message is so ...
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1answer
85 views

If I import Ownable and MyClass inherits from it, do I need to migrate the Ownable at all?

I'm a bit confused about migrations. I've just been told to use 1_migration.js file per contract, except maybe in the case of imports. I am going to change these migrations back to one per migration, ...
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1answer
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Multiple inherintance: solidity docs example explanation

I found this example on the docs: pragma solidity ^0.4.22; contract owned { constructor() { owner = msg.sender; } address owner; } // Use `is` to derive from another contract. Derived // ...