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Questions tagged [constructor]

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1answer
26 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
16 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 ...
0
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1answer
50 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 ...
0
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1answer
8 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
44 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. ...
2
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3answers
44 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: ...
0
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1answer
280 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{ ...
1
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2answers
60 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(...
1
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1answer
62 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: ...
1
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1answer
37 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 ...
0
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1answer
55 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. ...
1
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1answer
95 views

Solidity Constructor Parameter List

can someone list the parameter types accepted by a constructor in solidity .. in particular, can we do something like passing an actual contract in a constructor's parameter list, for example: ...
0
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1answer
23 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 ...
1
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1answer
42 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, ...
1
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1answer
76 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
110 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 { ...
1
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1answer
63 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 ...
1
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0answers
78 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 = ...
0
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1answer
60 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 ...
0
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1answer
37 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
136 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.
0
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1answer
274 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 ...
0
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1answer
85 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. ...
0
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1answer
28 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?
0
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1answer
257 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
104 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 { ^ (...
0
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1answer
310 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. ...
2
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0answers
237 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
379 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 ...
1
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2answers
357 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 { ...
1
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2answers
88 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; } } ...
0
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2answers
76 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 ...
1
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1answer
325 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(..) ...
0
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1answer
769 views

Using constructor() and the fallback function in the same contract gives error

I'm trying to compile something that mirror a pattern like this and getting the following error from remix: "browser/ballot.sol:26:3: DeclarationError: Function with same name and arguments defined ...
0
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1answer
644 views

Transfer ownership of a contract in the constructor

I'm trying to create a contract, and set its owner at the same time contract ERC721CrowdSale is Ownable { ... }//contract is in the same file and has access to methods contract CS_Creator is Ownable{...
0
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1answer
599 views

The constructor should be payable if you send value

I have written a contract as follows: pragma solidity ^0.4.0; /* Simple contract that mediates disputes using a trusted arbiter */ contract Taxi { enum State {IDLE, FINDING_DRIVER, ...
1
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1answer
695 views

Dynamic Arrays in solidity Structs

I have question about creating Struct where size of array passed to that struct could have different lengths. As in code below I could pass to this Recipe 2 ingredients, 3 ingredients or whatever ...
3
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1answer
408 views

Multiple inheritance and order of chaining of multiple base constructors [duplicate]

I am trying to understand the order of invocation of base class constructors in the presence of multiple inheritance. As far as I can tell, the order appears under-specified in the Solidity ...
1
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2answers
2k views

Does Solidity support passing an array of strings to a contract's constructor yet?

I am going through a tutorial from 2017 that says it was updated in January of 2018. It says that currently you can not pass an array of strings directly to the constructor of a contract and that you ...
2
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0answers
24 views

Why not possible limiting gas but forwarding ether in creating this contract from Solidity documentation

In the Solidity docs Creating contracts via new there is an example: contract D { uint x; function D(uint a) public payable { x = a; } } and it states in the accompanying text: ...
0
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1answer
24 views

Setting mapping value in constructor has no effect?

In the following smart contract: pragma solidity ^0.4.20; contract MyCoin { uint _totalSupply; mapping(address => uint) public balances; function MyCoin() public { _totalSupply = 1; ...
1
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1answer
462 views

What is the significance of making constructor payable?

Aren`t constructors used to initialize variable at the time of contract creation? In common patterns section in solidity documentation, payable constructor is used for withdrawal pattern example. ...
1
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1answer
248 views

Best way to send an address to the constructor in Remix?

I know how to pass an ETH address to the constructor in truffle. What is the best way to do it in Remix? Say contract A is in Remix to create Tokens and contract B (another solidity file) is the ...
0
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2answers
154 views

Access deployed contract's constructor's parameters from address

I'm using ethers.js but any answer will be okay ! I'm trying to access a contract's constructor's parameters that was used when deployed to make sure the contract has not been modified before being ...
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1answer
87 views

Why would data be passed into a contract constructor rather than just hardcoding it, which would be less costly?

Doesn't it cost more to pass in variable assignment via a constructor due to changing state? Wouldn't it be cheaper to just assign them in the code? I am wondering if there are advantages to using ...
0
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1answer
435 views

Constructor Arguments for verification on Etherscan.io

I want to verify a contract on Etherscan.io, but I am not able to find the correct Constructor Arguments. I tried everything which is explained on StackExchange, but cannot get it to verify... The ...
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1answer
325 views

Why use constructor function?

What is the big difference between: contract Crowdsale { MintableToken public token; uint256 public someInt; [...] function Crowdsale (uint256 _constructorArgument){ someInt = ...
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2answers
4k views

Should the constructor function be public?

In all the tutorials I'm watching nobody specifies public, but remix presents warnings that function visibility has not been specified, and public is assumed. Since I don't like warnings if possible,...
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2answers
3k views

Is address(this) a valid address in a contract's constructor?

When does a smart contract's address first become valid? Is the address during the execution of the contract, or only after it's been fully instantiated and initialized? In other words, is a contract'...
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1answer
331 views

Is it ok to pass function's call as arguments to functions in Solidity?

So basically, is it ok to call fun() as an argument like ethToWeiConverter in the example below? Otherwise, what style is preferable? contract RefundableCrowdsale { uint256 cap; ...