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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questions
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How can you know the length of array of dyanmic strcutures?
pragma solidity ^0.4.24;
contract online_shopping{
struct item {
uint price;
string name;
//string seller;
}
struct soldItems{
address customer;
uint tprice;
}
mapping (address=...
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1answer
12 views
Factory for ERC1400, deployed contract not working
Hey I have written a factory for the ERC1400 Token by https://github.com/ConsenSys/ERC1400. When I run the test for issueByPartition I get a revert Error. Other tests like isIssuable works.
If I ...
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0answers
7 views
How to signTransaction of a smart contract methods?
I have a smart contract contains this method:
function addOneUser (User memory _user) public {
bytes32 hash = keccak256(abi.encode(_user.name));
users[hash] = _user;
}
I want ...
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0answers
9 views
Payable function not working properly
Hi everyone hope I will be clear enough with the explanation because I couldn't find a proper solution.
I am just trying to checkout an item with my buy function but it seems like I am stuck.Here is ...
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1answer
18 views
how to correct this code with pragma solidity^ 0.5.8? thx
pragma solidity ^0.5.8;
contract HelloWorld {
function test() pure returns (string) {
return "HelloWorld";
}
}
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1answer
15 views
I would like to 3 mappings
I am a beginner.
I would like to 3 mappings
I know 2 mapping looks like this:
mapping (address => mapping (address => uint256)) public allowed;
and my question is: is 3 mappings look like ...
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0answers
22 views
I am newbie here,I need some help in retrieving one particular use using a userid, how do we do that as per below code?
struct Rider{
//address riderAddr;
uint rider_Id;
bytes32 Rname;
bool set;
}
mapping(address => Rider) public riders;
function registerRider(address _riderAddr, uint _riderId, ...
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0answers
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ParserError: Expected pragma
Hi guys.
I have got one big problem. When i try to compile my code i'm getting some kind of unusuall error.
I think everything is ok but when i try to "node compile.js" my main file ("inbox.sol") ...
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0answers
9 views
How can I distribute funds to present stakers efficiently?
I am building a smart contract which keep the token holder's eths for a while and give them rewards when they withdraw. The reward is given from the ethers collected by early withdraw of people. If ...
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2answers
11 views
Why am I getting TypeError: Member “balanceOf” not found or not visible after argument?
On line 22 my code is -- require(tokenContract.balanceOf(this) >= _numberOfTokens);
This gives the error message
TypeError: Member "balanceOf" not found or not visible after argument-dependent ...
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1answer
20 views
“onlyOwner” Function restrict the call from child contract
I have a basic knowledge of solidity. I am trying to create an upgradable ERC20 Token. For that, I create TokenStorage contract and Logic contract and trying to write the Proxy contract.
In the Logic ...
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1answer
23 views
Function should return all objects stored in the mapping array
Here's my solidity code. And I want all the objects to be returned stored in mapping array contracts in the getContract method by giving address as a parameter to the getContract function.
pragma ...
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2answers
46 views
How to get response from Solidity Smart contract by Web3 client?
Here is the Smart contract code. I want to get the result of function of UserRegister by using web3.
function UserRegister(string memory userName,uint feiyong ) public payable returns(string ...
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1answer
19 views
Decentralized database for ethereum?
I'm looking for a way to store data in a decentralized way such that I can access any record from within the smart contract, probably through oracles I guess?
I've been looking into gundb but not ...
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1answer
23 views
TypeError: Cannot read property 'nodes' of undefined
I'm new to ethereum, and I'm trying to test the depositToken function of etherdelta on linux, which version is 0.4.9, and the token I use is vixcore which version is 0.4.24, and I got this error when ...
1
vote
1answer
11 views
Uncaught (in promise) Error: Contract has not been deployed to detected network (network/artifact mismatch)
The client side application always throws the above error. I have connected the ganache account(by copying the private key)also with the correct port number in Metamask extension as well as in the ...
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0answers
10 views
How to filter by string parameter , web3 2.0.0-alpha.1 Solidity events?
I'm trying to filter some events , and I noticed since I updated the web3 to version 2.0.0-alpha 1 the event catch is a little bit different.
I have a Smart Contract with this event :
event ...
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0answers
25 views
VM error: revert. revert The transaction has been reverted to the initial state. Note: The called function should be payable if
Hi Guys 👋
I have two contacts first one is SubToken and second one is MainContract.
First I deploy MainContract after that I use createNewContract function and I create new SubToken.
and then
I ...
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2answers
25 views
ParserError: Expected pragma, import directive or contract /interface/library definition
In an attempt to compile my ABI and verify my contract, I am getting the following warning: "ParserError: Expected pragma, import directive or contract /interface/library definition" on the first line ...
1
vote
1answer
17 views
Trouble accessing an array inside a struct inside a mapping via web3
Here are a few relevant code snippets from my smart contract
struct Constituency{
uint16 id;
string name;
uint64[] cans;
}
mapping(uint => Constituency) public constituencies;
...
2
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1answer
26 views
TypeError: Indexed expression has to be a type, mapping or array (is function (address) view external returns (string memory,string memory…)
I have 2 contracts first one is sub second one is main .
First i deploy main and create a new subtoken.
Then I want to access my maincontract in subToken contract but I cant :(
When I compile this ...
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0answers
18 views
What does mean $(sai tub) and $(sai tap) in SAI readme.md
I try to deploy and use https://github.com/makerdao/sai/( SAI ) on my private blockchain. I deployed SAI with scripts (bin/deploy-fab && bin/deploy) without any mistake.
In https://github....
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0answers
35 views
Transactions go to an older contract address rather than the present deployed one
Though I have deployed a new contract but the transactions go to a previously deployed contract in my application. I'm attaching the screenshot of my Remix-ide code and the code for the front end ...
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1answer
18 views
Why am I getting a Parse Error in my smart contract after the constructor?
I'm writing a token sale smart contract & my original error was my function had the same name as the contract and I changed it to a constructor because the contract cant have the same name as the ...
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0answers
23 views
VS code Expected identifier, got 'LParen'solc
I keep getting this error/warning on my vscode when I emit events and build constructors.
or
After a bit of googling I understand it is something about my compiler, since solc <0.4.18 does not ...
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0answers
20 views
No Events After Deploying Another Contract in Remix
I am trying to write an upgradable smart contract in Remix. This involves a Proxy contract, a Logic_0_1_0 contract, and a Logic_0_2_0 contract.
I uploaded Proxy and Logic_0_1_0 only, and the ...
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2answers
32 views
“Gas estimation failed” on Ropsten with Invalid RPC JSON
I'm running into an issue going through a basic example in "Mastering Ethereum"...
I have a Faucet contract (on Ropsten) per the book that looks like...
pragma solidity ^0.5.1; //mastering ethereum ...
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1answer
21 views
Getting an error when (attempting to) using Web3js
I'm trying to connect a smart contract to a very simply front end that has html/css/js. I keep getting an error when trying to use web3 to connect - I have the code below but the terminal is giving ...
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1answer
10 views
ganache test returns characters instead of numbers
mapping(uint256 => uint256) public amount;
function saveAmount(uint256 _id, uint256 _amount) public {
amount[_id] = _amount;
}
I have a function that saves amount in mapping. When I test ...
0
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1answer
14 views
How do I check If a map entry doesn't exist for a given sender?
I have a map such as:
mapping (address => bytes32) private myMap;
Later in the code, in a function, I want to ensure my sender already has an entry in that given map.
Can I do this?
require(!...
1
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1answer
16 views
VS Code and Solidity files have a lot of warnings
Every time I use VS Code to develop Solidity, files I have a lot of this weird warnings saying:
no-trailing-whitespace: Line contains trailing whitespace
I googled a bit and I understand why they ...
1
vote
1answer
21 views
Is it possible to manipulate maximum callstack size in solidity?
I'm a student learning about solidity language.
According to solidity's official docs, the maximum callstack size is 1024.
But, I am wondering, can a developer change the maximum callstack size in ...
1
vote
1answer
29 views
How to construct deployable bytecode from runtime bytecode?
For example I want to redeploy/clone a contract to another address but don't have the original source code, so I only have the runtime bytecode stored on the blockchain. If I try to deploy the runtime ...
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1answer
28 views
Are memory variables initialized by solidity?
I've the following struct
struct Vote {
uint amount;
uint count;
}
Is it initialized when allocated in memory?
function boofar(uint val) public {
Vote memory result;
result.amount += val;
}
...
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3answers
33 views
Is it possible to find out dynamic array size looking at a smart contract?
This question already answers that in order to get the size of an array programmaticaly, a getter should be defined.
However, assuming that there isn't a getter, is there a way to find out size of a ...
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0answers
15 views
Ethereum Name Service implementation
I would like to create a Smart Contract that implements a name service.
It will allow anyone to register a name. Once a name is registered and associated with an address, it belongs to that address. ...
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0answers
17 views
Solidity Error: Cannot destructure property `interface` of 'undefined' or 'null'
I've got his error in Solidity when compiling my test file:
TypeError: Cannot destructure property interface of 'undefined' or 'null'.
I know it is related to my compile.js file, but what is ...
0
votes
1answer
24 views
Web3 - Access return value of events
I want to get the value that my smart contract returns in javascript.
Here is the contract. (version 0.4.25 - web3 version 1.2)
pragma solidity ^0.4.25;
contract SimpleStorage {
uint public ...
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1answer
8 views
How does the named return variables in solidity work
I have below solidity contract from Truffle quick start guide.
pragma solidity >=0.4.0 <0.6.0;
contract TaskMaster {
mapping (address=>uint) public balances;
...
0
votes
1answer
22 views
Can't log struct member in truffle test
Contract :
mapping (bytes32 => MyStruct) public myMapping;
struct MyStruct {
uint256 myMember;
uint256 someOtherMember;
}
Test (Truffle)
This works:
let ...
0
votes
1answer
20 views
Code:const web3 = new Web3(window.web3.currentProvider) Error: window.web3 is undefined
I am going to connect my contract with the website.However,there was something wrong with the web3? I'm not sure.
import Web3 from "web3";
const web3 = new Web3(window.web3.currentProvider);
const ...
0
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1answer
28 views
Is msg.sender.send(msg.value); safe?
Is there any sort of reentrancy attack that could go along with using this line of code in my smart contract?
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1answer
15 views
Can i use a the msg.sender which is a address to call a function of the contract?
I am trying to mint a ERC721 token using openzeppilin/contracts. It was working correctly, but later had to change the design. So now i am forced to use the msg.sender who is the minter to call the ...
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0answers
27 views
Error: Operator << not compatible with types bytes1 and int_const 1 return b10 << 1;
I don't know how to correct the code of function 4 & 5.
pragma solidity ^0.4.4;
contract C {
bytes1 b10 = 0x6c;// l-> 0110 1100 6c转换为10进制-》12*16^0+6*16^1=108
bytes1 b11 = 0x69;
...
0
votes
1answer
35 views
Event emits multiple times on a solidity function call
I need have a problem, when I execute a solidity function, event emits multiple times, but when I refresh page then it works normally and only past events get called.
Here is my code:
...
0
votes
1answer
18 views
Call to other contract method return false when two parameters are passed
Caller Contract
Called.call(abi.encodeWithSignature("test(address, address)"),empAddress, empContAddress)
Called Contract
event ad(address);
function test(address e, address f)public{
...
1
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1answer
26 views
Solidity - Return value of Smart Contract Transact
Why do Solidity transact functions not return any value?
Here is an easy example. I tested it in remix and web3.
pragma solidity ^0.4.25;
contract SimpleStorage {
uint public storedData;
...
0
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2answers
38 views
Why is storing via sstore more expensive than via events mechanism?
I just do not understand why emit Event(...) is cheaper than a = b. The only difference I noted between events and storage variables is that event logs is not accessible from Solidity. But both of ...
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1answer
19 views
How to do the Smart Contract Storage Migration using Quorum?
I wrote one smart contract without upgradable logic, now I want to update the same smart contract with some changes. Is it possible to copy the data from old contract storage to a new one?
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0answers
34 views
Error: Member “transfer” not found or not visible after argument-dependent lookup in address 0.4.4 [duplicate]
pragma solidity ^0.4.4;
contract PayableWorld {
function deposite () payable{
address dyw2 = 0x1De57DD112092D60F45c9e2045424003e6B2C75a;
dyw2.transfer(msg.value);
}
how can i change the ...
