Questions tagged [constructor]

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26 views

Can someone read this private variable?

my purpose is to generate a random key when the smart contract is created and save that key in a private variable. I don't what to know its value either. Let's take for example the code below: pragma ...
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1answer
22 views

What happens when a Contract is added to the genesis block?

Recently I found out that you can add smart-contracts to the genesis block (genesis.json) of your local ethereum network. Since normally, when you add a smart-contract via a transaction, you can call ...
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How to listen for contract creation, or all block events?

I'm building a web app with web3 where users can deploy a certain contract and assign some people to it. Inside the constructor of that contract I also output a certain event. I want these assigned ...
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Passing constructor arguments from child contract to parent contract

The ERC721 standard contract requires a token name and symbol in its constructor. I have inheritance pattern that looks likes Contract A is B and Contract B is ERC721. If I want to set my token name ...
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1answer
46 views

How do I set the constructor arguments when deploying using OpenZeppelin CLI?

My Token contract compiles fine using solidity 0.5.0: import "/Users/lennard/Desktop/GGToken/node_modules/@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol"; import "/Users/lennard/Desktop/...
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1answer
22 views

can a hacker call constructor() function after deploy if it is public? [duplicate]

Is below function can be called by a hacker after deploy constructor() public { test = true; }
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1answer
186 views

Error: This contract may be abstract

My solidity contract compiles in Remix, but when I try to deploy it it fails and throws Error: This contract may be abstract, not implement an abstract parent's methods completely or not invoke an ...
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1answer
25 views

Trouble deploying one contract from another

Why creating a contract new RewardCourts() in another contract takes more than ten kilobytes of bytecode in the contract it is called from? (It makes bytecode too big and I can't deploy it!) What to ...
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1answer
34 views

Payable constructor gives revert message

I am trying to execute the following contract on remixe IDE: pragma solidity ^0.5.4; contract GuessTheNumberChallenge { constructor() public payable { require(msg.value == 1 ether); } ...
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3answers
96 views

Passing constructor arguments to the CREATE assembly instruction in solidity

I have a contract which deploys other contracts by bytecode: contract DeployContract { function deploy(bytes calldata _bytecode) external returns(address addr) { bytes memory bytecode = ...
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1answer
75 views

How to share TypeScript code between truffle tests?

I have some code in my TypeScript tests, say: function foo() { return 'bar'; } which I'd like to share with all my tests. The simple solution is to copy the function into each *_test.ts file. ...
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1answer
29 views

Error: invalid address in solidity constructor

I get a huge error message (~1MB) starting with Error: invalid address (arg="_readAccess", coderType="address", value={"constructor":{"contractName":"SenderAccess","abi":[... when executing a test ...
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1answer
56 views

Stack too deep problem

I try to add more property to the scenario struct but when I run the compile the same error appear: struct Scenario { uint id; address payable author; address editor; ...
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1answer
80 views

Can you emit events in a contract constructor?

I have a constructor that is emitting an event, but cannot seem to see/catch/filter that event after deployment.
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2answers
185 views

Remix: 0x0 Transaction mined but execution failed due to construction

I have the following example smart contract, where I cannot deploy using remix into my private network using environment Web3 provider. The error I am getting is Transaction mined but execution failed ...
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1answer
250 views

Uncaught TypeError: web3.eth.Contract is not a constructor

For whatever reason, when I attempt to set an instance of a contract in a javascript file, I get the following message in my console: Uncaught TypeError: web3.eth.Contract is not a constructor At ...
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1answer
96 views

Storing geo location in contract

I am beginner in solidity programming, I am trying to write my first contract. I am trying to store a piece of land (which is array of coordinates) against a person. I am having trouble storing the ...
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1answer
115 views

passing variables between different contract by solidity (0.5.0+ version)

I writed ERC20 contract and ICO contract for a test , but I meet a lot problem with compile problem. My ERC20 contract have own constructor but,I also need a ICO contract(a control)for passing ...
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0answers
18 views

Unexpected behaviour. Huge size increase when adding new SubContract()

I have a contract similar to: contract Contract01 { SubContract _refContract; ... constructor() public { refContract = new SubContract(); } function setSubContractRef(SubContract ...
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1answer
228 views

How to pass arguments to token smart contract generator?

I'm trying to build a 'token generator' smart contract that accepts 3 arguments to then deploy a new token smart contract with those inputs ('strings' for symbol, name, 'address' for owner). I am a ...
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1answer
15 views

Function inside constructor is called from which address?

interface token { function transferFrom(address _from, address _to, uint256 _value) external returns (bool success);} contract CampaignFactory{ token public token_instance; constructor()...
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1answer
182 views

Solidity : Error when pushing an address into a dynamic address type array

I'm trying to insert an address into an address type dynamic array. It works well when I do the operation inside a function. There are no errors and the elements are properly pushed into the array. ...
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3answers
154 views

Is a constructor needed to set a contract owner?

until now I have set the owner in a contract like so: pragma solidity ^0.5.2; contract SampleContract{ address payable owner = msg.sender; } in the docs it is suggested to do it this way: ...
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1answer
797 views

Contract deployment using web3.eth.contract(abi) with constructor arguments

I'm trying to deploy the following smart contract: pragma solidity ^0.5.00; contract TestContract { address public owner; string public word; constructor(string memory _word) public{ ...
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2answers
305 views

Encode constructor arguments used when deploying a contract

How can I encode the constructor arguments when deploying a contract? Here is my deployment function: async function deploy(abi, bin, args) { let contract = new this.web3.eth.Contract(JSON.parse(...
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1answer
164 views

What does etherscan mean by “Constructor Arguments (ABI-Encoded and is the last bytes of the Contract Creation Code above)”?

I'm inspecting a contract on etherscan, at the following URL: https://etherscan.io/address/0x5cb5f46a655c02889172323760d12d0e5d83cdaf#code At the bottom of the web-page, I see two sections: ...
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1answer
155 views

How can I retrieve the constructor arguments used during contract deployment

I know how to extract the constructor arguments out of the transaction object returned from a contract-deployment operation. It is explain in web3.js official documentation here. But this is not an ...
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1answer
143 views

Making a contract with new keyword address is always 0x0000000000000000000000000000000000000000

I'm making a contract that makes other contracts. Once the contract is made using address tokenAddress = new MyToken('Name'); I want to save the address of the contract, tokenAddress, in MyStruct. ...
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1answer
233 views

Solidity Constructor Parameter List

Which variables types are accepted by a constructor in Solidity? In particular, is it possible to pass an actual contract as an constructor input? For example: contract ContractA { constructor (...
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1answer
40 views

Constructor Function: How can I tell which function is the constructor?

How can I tell which function is the constructor function? In the OpenZeppelin implementation of the MultisigWallet, OpenZeppelin claims this is the constructor function: /** * Constructor, sets ...
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1answer
55 views

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, ...
2
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1answer
131 views

Getting and storing address of erc20 contract after dynamically creating it

I have a function which dynamically creates an ERC20 contract on calling a function in another contract as follows: function createDao(string _tokenName) public payable { tokenNumberIndex = ...
2
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1answer
276 views

How does a contract's constructor work and load input values?

I set up the following contract: pragma solidity ^0.4.25; contract Simplest { uint x; constructor(bool _lucky) public { if (_lucky == true) { x = 7; } else { ...
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1answer
97 views

problem with constructor parameter in rawtransaction

I am using remix and ganache to test out my contract. The contract deploys successfully, however, I do not see the state variables initialized with the constructor parameters when I look at the ...
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0answers
104 views

the constructor should be payable if you send

I have been testing the code and for some reason I am having a block. The error is described as "the constructor should be payable if you send value". The debugger points to " uint256 weiAmount = ...
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1answer
69 views

Smart Contract Testing

I am writing test driven smart contracts. There is one smart contract with parameterized constructor. And I am using the require statement in the constructor. I want to catch the error in my test ...
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1answer
67 views

When extending a contract how to call the external constructor and pass parameters?

I have the following contract import "zeppelin-solidity/contracts/token/ERC721/ERC721Token.sol"; contract Contract is ERC721Token { function Contract(string _name, string _symbol) public { ...
4
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1answer
174 views

Purpose of the function with the contract's name?

What is the purpose of the WithdrawalContract function in this case? If becomeRichest doing exactly same but with a certain condition and adding a pending withdrawal to the pendingWithdrawals.
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1answer
418 views

Deploying a contract with a “payable” constructor and including input parameters?

There is a useful Solidity contract HERE. However, there are two things at time of its deployment: (1) The first thing is the contract balance since its constructor is payable. (2) And the second ...
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1answer
185 views

Solidity state variable resets to default inside function

For this project, I am coding smart contracts for Ethereum using Solidity. In the following code, the variable numCertificates should initially be 1. Nonetheless, newCertificateId is 0 when assigned. ...
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1answer
40 views

Advantage of using a contract contructor with parameters

What is the advantage of using a constructor with parameters instead of hard coding the values? Is there a possibility to reuse a once deployed contract?
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1answer
374 views

Fixing warning about “constructors” causes new error referencing the old function name [duplicate]

I'm using the solidity code for deploying new ERC20 tokens found here and quoted below: pragma solidity ^0.4.16; contract owned { address public owner; function owned() public { ...
3
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1answer
120 views

v0.4.22 solc compile failing - not predictable behavior

Error: Warning: Defining constructors as functions with the same name as the contract is deprecated. Use "constructor(...) { ... }" instead. function CappedCrowdsale(uint256 _cap) public { ^ (...
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1answer
547 views

address.transfer(value) is throwing error in solidity contract.

I am building an approval contract in Remix and have been stuck on this issue. When I try to transfer wei using address.transfer(value), it throws an error. I have marked it in the code below. ...
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0answers
305 views

Passing struct into new contract through constructor

I have a function in my ChangeManager contract which should create multiple ChangeRequests. I tried to model a Change by using a struct and pass this from my ChangeManager to the ChangeRequest: Code ...
2
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1answer
754 views

Can a function with the same name as the contract be declared both as a function and a constructor?

A function with the same name as the contract is normally a constructor and it’s bytecode isn’t included in the resulting contract. But is there a way to declare a function with the same name as the ...
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2answers
615 views

Contract inheritance

I really hope this is not a dumb question. I am trying to call the constructors of the inherited contracts in a structure like this: contract A{ uint a; constructor (uint _a) public { ...
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2answers
148 views

Multiple constructor functions - Will they be executed once?

let's say I have the following contract/solidity file: pragma solidity ^0.4.20; contract partOne { address public owner; function partOne() public { owner = msg.sender; } } ...
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2answers
93 views

Correcting Code for Constructor

This StackExchange question ALMOST answered my question. However I don't know how to exactly correct my code so that the function named after the contract is replaced by the constructor. How ...
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1answer
379 views

Ethereum Solidity how to deploy a contract from another contract with constructor function

The old way: constructor function is the same as the contract name: contract CtrtFactory { function makeCtrt() { address ctrtAddress = new Ctrt(...); } } contract Ctrt() { function Ctrt(..) ...