Questions tagged [solidity]

Solidity is a contract-oriented, high-level language whose syntax is similar to that of JavaScript and it is designed for writing smart contracts in Ethereum to run on the EVM. Solidity is statically typed, supports inheritance, libraries and complex user-defined types among other features.

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How does the Solidity compiler translate the `using .. for` statement?

I'm trying to figure out how using [Library] for [type] is compiled by the solc compiler. I noticed that address placeholders are not in the bytecode as with other library references. So what ...
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Call a payable contract's function from another contract via an interface

I have two contracts, they are connected via an interface. When user calls contract1 function, it uses an interface to call contract2 function which updates it's storage. My problem is that I can ...
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How to get the return type of a function of an already deployed contract?

I am currently working on a real estate blockchain project. Now I have 2 contracts user.sol and property.sol. The person who is registered on the website through user.sol can only buy or sell property ...
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How can I execute transferFrom function in node js

There is solidity erc865 code function transferFromPreSigned( bytes _signature, address _from, address _to, uint256 _value, uint256 _fee, uint256 _nonce ) public ...
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Can I send transaction to a view|pure function?

This is the contract: uint public result; address public owner; constructor() public { owner = msg.sender; } function add(uint a, uint b) public returns(uint) { result = a + b; return ...
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Unable to call setter function in solidity using Infura

Solidity code contract Greeter { string public greeting; function Greeter() public { greeting = 'Hello'; } function setGreeting(string _greeting) public { greeting = _greeting; } function ...
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1answer
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Error whilst running solidity with python(py-solc)

I have been running my code which involves deployment of smart contract to Ethereum Ropsten network. I ran this successfully for some time but last week did installed another software after which ...
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How to add function buy to buy button that need array index

I am new to this smart contract and blockchain. I'm trying to do simple selling goods dapps. But i'm stuck at the buy button. I have array for the products. constructor() public { goods[0].owner =...
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1answer
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mapping data is not returned from SmartContract during the first time add operation

I have the below given SmartContract and the test. Please note that, when i try to execute the test, only after the second call to the grantAccess method, I am able to get the mapped value. pragma ...
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1answer
355 views

Passing one contract instance as an argument to the constructor of another contract

I need to use the functions of the ERC20 contract in another contract. The ERC20 contract is from the openZeppelin contract library. I found the following code on a website: import "../../...
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Using OpenZeppelin's increaseTime.js

I'm writing a test for a time-dependent solidity function. I'd like to use the increaseTime.js helper from v1.12.0 of OpenZeppelin's library. When I try to call this helper inside my test, I get an ...
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web3 - get all contract public variables?

I have an abstract worker contract and few that inherit from it. Those contracts have some public variables, each one different. I want to display them on my website. Is there any way to return all ...
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One time catastrophic solidity bug suddenly vanished

I'm writing a Blackjack game in solidity. In the following function, the player ended up winning one time with a hand strength of 30 after doubling down even though they should have busted. ...
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1answer
288 views

How to implement percentage deposit function to smart contract

I need to implement on the deposit function when the ownerAddress is doing a deposit a 10% to be freeze in the smart contract and and if the ownerAddress want's to call the returnDeposit function by ...
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Why is putting data to storage more expensive during the deployment of contract than storing the same data by a method?

I am working with truffle and solidity (v0.4.23) and found out that when I pass in an argument of constructor some bigger amount of data (16kB) that are saved to storage of a smart contract, it is ...
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1answer
47 views

Why use different gas?

I have this contract with this functions, why each use different gas amount? pragma solidity 0.4.24; contract Foo { //transaction cost: 21471 gas //execution cost: 199 gas //total cost: 21670 ...
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Can I call a library function from a payable function?

I seem to get a revert each time I try this. I'm unable to get any useful revert message from truffle, so any assistance there might also help solve this. I have a library: library LibInterface { ....
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1answer
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Can't call a function in a contract, returning something from another contract

I use private geth + web3js (in truffle this works good) Here is an example worked as expected: the first contract: pragma solidity ^0.4.24; import "./Second.sol"; contract First { Second ...
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1answer
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How to process Smart Contracts payable functions in batch?

I am aware that metamask will enable effective security for processing via the web browser a payable function action to a smart contract. What happens in batch? I have an API service which then ...
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1answer
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Transaction execution and interacting with truffle

pragma solidity ^0.4.23; contract Hotelbooking{ address receiver; function deposit(uint256 _amount) payable public { require(msg.value == _amount); // nothing else to do! ...
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Truffle interaction with my smart contract getting Vm exception

pragma solidity ^0.4.23; contract Hotelbooking { event Transfer( address indexed _from, address indexed _to, uint256 _value ); mapping(address => uint256) public ...
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STOP after RETURN in bytecode generated by solidity

I am currently analyzing the code generated by the solidity compiler. Let's take this simple example: pragma solidity^0.4.24; contract test { constructor() public { } } The code generated with ...
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1answer
170 views

Transmit array as first parameter in web3.js

When I develop in solidity combined with web3.js, I face some problem recently. I create a contract code below //setContractDetail(index,bool isConsentItem,uint8[] detailItems) function ...
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What is the command PUSH29 010..00 in solidity compiled bytecode?

If you take a look to the bytecode of several contracts compiled from solidity you can notice that in the first ".data" basic block there is this command: PUSH29 ...
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Interacting with a complex deployed contract from my other contract

For example, I want to call a create market function from augur in my contract. I'm using the recommended pattern, but there are additional contracts that this function brings in, ex ICash, IMarket ...
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521 views

Contract too large

I am sure this has already been answered but I could not find a clear answer. I get the following error: Contract creation initialization returns data with length of more than 24576 bytes. The ...
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How does createProxyImpl work in ProxyFactory Contract?

function createProxyImpl(address _target, bytes _data) internal returns (address proxyContract) { assembly { let contractCode := mload(0x40) // Find empty storage location using "...
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Contract - Demo - Identifier - Only 3 Lines for my contract to work - ¿does somebody know how to fix this?

pragma solidity ^0.4.23; contract Owned { address owner; function owned() public { owner = msg.sender; } modifier onlyOwner { require(msg.sender == owner); ...
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1answer
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call other contract's external function , the error: The contract code couldn't be stored, please check your gas amount

when I deploy a contract, the truffle frame told me this error :“The contract code couldn't be stored, please check your gas amount”。 the solidity code is: 1) Base.sol pragma solidity ^0.4.22; ...
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msg.sender is not showing corect value

I am facing a strange issue. Please read the below case craefully and assit me to geth this issue resolved. I have ERC20Token created by Zeppling templates. [Please ignore syntaxes, I am just trying ...
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Is returning an array of structs possible yet?

From what I can tell this should be possible now: function test2 () public view returns (Post[]) { Post memory post; post.sender = msg.sender; post.link = "test"; ...
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Solidity Event logs

I have a JS code which is connected to ganache. I am trying to call a solidity function which in tern emit the event. In JS i am watching the event. Now when i call the function first time it sets ...
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Signature generated through web3.eth.sign not leading to same address after fromRpcSig

I am trying to write sign a challenge using web3.eth.sign, web3 uses ganache.provider(), But when i do fromRpcSig(signature) ecrecover(challenge) which results in different address. But when i sign ...
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Estimated gas is always low

web3.eth.estimateGas is always calculating low gas for the transaction. Here is a reference to a trasaction in ropsten. https://ropsten.etherscan.io/tx/...
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Getting Json file from remix

I have been deploying contracts on rinkeby but we are almost done to go to mainnet. I have been comparing deployments with truffle and remix and there is a huge difference in gas uses, so I would ...
2
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1answer
166 views

Created Crowdsales contract, sending ropsten ETH to the contract and Failed

I created crowdsale contract - https://ropsten.etherscan.io/address/0xfbb2759ef0b7169d0a2effa971845ea0f99f87b1 My token - https://ropsten.etherscan.io/token/0x0f26c1c05f1bbBC7Eff0488F1a98619e8a9758cf ...
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1answer
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Any way to do compile-time computation using rational_const and a constant value?

Of the following three declarations ufixed constant TEST1 = 256; uint constant TEST2 = 256; uint[] testTable1 = [uint(0.001 * TEST1), uint(0.01 * TEST1), uint(1.1 * TEST1)]; uint[] testTable2 = [uint(...
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1answer
139 views

Function to return tuples throws error on frontend

I have similar functions like this and they work fine: function getBarsOfParticipant() external view returns (uint256[], uint16[], bool[]) { uint256[] barIds = participantToBarIds[msg.sender];...
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1answer
557 views

web3.py constructor(address type)

I tried to deploy the contract on my testrpc, but I get error when my constructor using "address" type. Here is my python code: import json import web3 from solc import compile_source from web3....
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3answers
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I am unable to verify my contract on etherscan

Unable to verify my contract on etherscan. This is the link - https://ropsten.etherscan.io/address/0xc68c67a1864060631817be1eebdb91e8661fae7a . Please help. Its urgent. Here is my code: pragma ...
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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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Gas Estimation Failed for Airdrop for sending Tokens to Multiple Addresses using Remix

I have deployed a Crowdsale contract and now I need to send my Tokens to a list of addresses using remix and injected web3. I am using below code for Airdrop but when I send tokens to multiple ...
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calling method from another contract throws Revert

I have a smart Contract "RecommendContract" contains this method: function addVacancy(address sender, bytes32 vacancyId, uint256 incentive) external { Vacancy vacancy = vacancies[...
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1answer
588 views

How to unsubscribe logs / events?

There are two ways to subscribe/watch to logs/events: Subscribe: var subscription = web3.eth.subscribe('logs', { address: '0x123456..', topics: ['0x12345...'] }, function(error, result){ ...
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Data Scientist wanting to simulate a DAO on private network, unsure of where to begin

My apologies for such a broad question, I couldn't find anything remotely similar to my case and I've got lots of questions - I'll try to narrow the scope down here. Premise: I'm a data science ...
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Comparing solidity sha3 with web3 sha3 inside smart-contract

The problem is that sha3 in solidity returns bytes32 and I have a string returned from IPFS by oraclize, and if hash calculated in solidity and returned to web3js (bytes32 got interpreted as a string) ...
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1answer
355 views

Calling function from another contract reverts

I've been developing a dApp that needs ERC721 tokens. I have three contracts, a base contract, the one to mint tokens and another one for auctions. The inheritance looks like Base > Token > Auctions. ...
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Which solidity dev environments support the use of already deployed library contracts?

So, I'm looking into using libraries in order to prevent re-deployment/re-use of the same code. I was hoping that I would be able to specify the address of a library in solidity code, using syntax ...
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1answer
1k views

Error from sendSignedTransaction: Error: Returned error: replacement transaction underpriced

I am the beginner in Ethereum stuff need guidance please help I am running a private ethereum network and using mist wallet here is my contract code pragma solidity ^0.4.0; contract MyFirstContract ...
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1answer
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How does Ethereum know who called a function first?

Scenerio 1 Say I have a function f(). Whoever calls the function first gets a reward. Persons A, B, and C all call the function at roughly the same time. Who will receive the reward? Scenerio 2 ...

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