Questions tagged [state-variable]
The state-variable tag has no usage guidance.
47
questions
0
votes
0answers
32 views
if “address public x = tx.origin”, why does “require (tx.origin == x”) work and "require (tx.origin==tx.origin) not
Below is a contract that i have commented on, hoping to understand the logic of the arguments.
Below in bold is the question in question. The .sol currently works fine.
pragma solidity ^0.5.11;
...
1
vote
1answer
26 views
Receiving error while getting state variable value after using selfdestruct method “Error: Returned values aren't valid, did it run Out of Gas?”
I am using selfdestruct method and passing the payable address to it but receiving the following error when trying to get the value of a state variable :
"Error: Returned values aren't valid, did it ...
0
votes
1answer
76 views
What is the immutable keyword in Solidity?
What is the immutable keyword in Solidity and how do I use it?
0
votes
1answer
35 views
Length of state array is not changeable in Solidity
Consider there are 3 contracts: BankA, customer, and BankB.BankA transfers some ethers to customer and after that some customer's state variables must be changed (in a better words be updated). It ...
0
votes
1answer
27 views
How Solidity field variable update is happening?
I am curious to know about, how the updation of field variables in solidity is happening ?. Whether world state is maintaining for each variable in the contract as like account balance?. And one more ...
1
vote
1answer
30 views
Why OpenZepplin always use private visibility for state variables?
Why OpenZepplin always use private visibility with getter functions for its state variables? I can't find a reason why they are not using public, is there any potential security or gas cost difference ...
1
vote
0answers
29 views
Retrieving a State_object value on go-ethereum
I have a deployed contract address and I need to query a contract storage value, a token account balance that is stored on a mapping variable:
mapping (address => uint256) balances;
From go-...
asked Aug 5 '19 at 9:49
Juan Ignacio Pérez Sacristán
2,7633 gold badges26 silver badges60 bronze badges
0
votes
1answer
75 views
Why string variable must be memory from solidity v5.0?
May someone explain me why exactly string variable must be memory from solidity v5.0 and what does tha mean?
Thanks for your help.
-1
votes
2answers
127 views
Truffle uint test script not updating storage variable, and strange behaviour
while testing I got a strange behavior of truffle, please see the subject smart contract code first
uint256 public burningRatePercent = 50;
function onlyOwnerSetBurningRate(uint256 ...
1
vote
2answers
113 views
Accessing private variables using assembly
I would like program an oracle service which I would like to charge a fee for. Therefore, I would store the data of interest as a private variable in my oracle contract. This private variable should ...
2
votes
1answer
18 views
defining storage literals in Solidity
I am trying to write unit tests on functions that take in a storage reference as parameters. There is not much great documentation around how to create literals for these types. These include: address ...
1
vote
2answers
196 views
state variable value not changing
I have very simple solidity code as below -
pragma solidity ^0.5.6;
contract SaveData {
uint public salary;
function setSalary(uint input) public {
salary=input;
}
function ...
1
vote
1answer
37 views
Does a storage array have a unique address on the block-chain?
The question in the title is a little vague, so I will try to explain here.
Suppose I have a contract with a storage array:
pragma solidity 0.4.24;
contract MyContract {
uint256[10] public ...
0
votes
1answer
121 views
dApp Tech Stack
So I'm looking into building a dApp with standard app I functionality like user login/posts/likes/comments etc. Along with harnessing the power of ethereum to support betting and donations. Here is ...
2
votes
1answer
439 views
How State variable are stored and updated?
The Smart contract and the state variables are stored in the blockchain, let us say during deployment of a smart contract the state variable and smart contracts are stored in the block 1, and in ...
1
vote
1answer
112 views
Are constant state variables cached in the EVM?
From the docs:
constant for state variables: Disallows assignment (except
initialisation), does not occupy storage slot.
Does this mean that the EVM caches constants across all contracts using ...
1
vote
1answer
36 views
Accessing the Ethereum State Variables using web3js (Java Script)
I'm trying to run the below code to get the state variables using the getIdBytes method of the Smart Contract, and assign it to a java script array variable, but it doesn't seem to work.
All I can ...
5
votes
1answer
301 views
What are 'payable' state variables?
https://solidity.readthedocs.io/en/latest/solidity-by-example.html#simple-open-auction
pragma solidity ^0.4.22;
contract SimpleAuction {
address payable public beneficiary;
What exactly does ...
0
votes
1answer
14 views
Setting Contract level variables
I'm a Python Developer jumping into Solidity and I feel like I'm missing something about variables and scope.
How do I set and access variables outside of a function's scope?
I can't seem to add ...
1
vote
2answers
238 views
Abi to call value
how to calculate ABI to call some variable in contract?
for example
contract X {
uint data;
function Y(uint a) {}
}
How to calculate signature to call variable "data" ?
I know to call ...
2
votes
1answer
922 views
What does “_” mean before a variable name?
I'm a beginner, just recently started reading the docs for Solidity.
I can't seem to find this anywhere on google. What does the underscore mean when placed with the indexed keyword?
Examples:
_from
...
1
vote
0answers
29 views
Best way to restore historical storage state
What is the best way to get historical storage state, given db with current world state and blockchain data?
Do I need to reverse assemby code or can I do this using receipt logs?
0
votes
2answers
287 views
In solidity smart contracts how do you access internal state variables declared in the constructor?
I'm working with a solidity contract that declares a state variable in the constructor like this this:
constructor(
address vault,
address proxy
)
public
MarginAdmin()
{
state ...
0
votes
0answers
45 views
Can we issue a token with specific local state?
Will it be possible to create an ERC20-Token, that will be "minted" with specific local state on a per token-basis while this state can change over time through the execution of a method in the smart ...
2
votes
1answer
395 views
Why public variables aren't able to implement interface functions?
I'm curious why interfaces don't accept public variables as implementations, since public variables have getter functions generated for them.
For example why couldn't the ERC20 balanceOf interface ...
1
vote
1answer
108 views
Why standard tokens manually create getters for balanceOf and totalSupply [duplicate]
I've been reading through different implementations of ERC20 tokens and I noticed that many of them define balanceOf[address] as balances[address] and then create a public getter() to match the ...
0
votes
2answers
784 views
How do I see the value of a string stored in a private variable? [duplicate]
I have read many times that sensitive data should never be stored in a transaction, but, specifically, how would the value of a state variable be read if marked private?
0
votes
0answers
157 views
How to interact with a smart contract to change a variable state
How do I change a variable in a smartcontract (bool)
As requested, a new followup question from the above^ about ethereum smart contracts (solidity)
If I have, early in the contract:
bool public ...
2
votes
1answer
316 views
local var inside a function modifies another state variable
I have this very simple contract:
pragma solidity ^0.4.18;
contract C{
uint public a = 9;
uint[] public data;
function f(uint _a) public{
a = _a;
uint[] y;
...
1
vote
1answer
101 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 ...
1
vote
1answer
799 views
Why do some variables' names end in underscore?
On Open Zeppelin's ERC20 BasicToken contract the variable totalSupply_ follows a naming convention I haven't seen before.
Is that to differentiate it from the function totalSupply() below or is there ...
0
votes
1answer
253 views
Reading variables from web3 (Documentation is out of date)
I'm trying to read an ownersNum public uint from my contract.
I instantiate in node:
l = console.log;
var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
let c = new web3....
0
votes
1answer
424 views
Calling a state-changing function via web3
I am trying to call a function which changes the length of a global storage array.
At first I thought that the problem was related to the array-length changing attempt.
But I have finally come to ...
0
votes
1answer
57 views
Unable to change the length of a global 2D storage array
I am facing difficulties changing the length of a global 2D storage array.
It seems to be working correctly on Remix IDE, but when I try to test it on ganache-cli (formerly known as testrpc) - either ...
1
vote
1answer
34 views
What is the length of an empty fixed sized array?
Let's say we initialize a state variable as:
uint[10] public fixed_array;
This is a fixed sized array which is currently empty.
What would fixed_array.length return? 0 or 10?
1
vote
1answer
445 views
Access previous state
Let's say I have a uint public myvar in my contract that is initialized to some value.
Then, myvar gets set to 3 in the next block.
How can I retrieve the old value? Is this possible with web3?
...
0
votes
1answer
271 views
I cant get the value of a state variable public
I am developing a smart contract which I have two contracts(A and B). I have an array variable in A and fill it with values but when I get that variable from B, the array address is empty.
pragma ...
3
votes
4answers
538 views
Conceptualizing smart contract variables
I'm having trouble figuring out how variables are stored on the block chain. How can a smart contract be immutable and have global variables that can change?
Just say I a simple contract like below......
2
votes
2answers
100 views
Is Solidity creating an implicit getter for a nested contract that is created?
Is Solidity creating an implicit getter or not for a nested contract that is created?
Example:
contract Foo {
....
}
contract Bar {
Foo public foo;
Bar() {
foo = new Foo();
}
...
3
votes
2answers
1k views
Why is uint so popular
Among every tutorial/real world example I have yet to come across anyone using the int datatype, I almost thought there wasn't one existing.. Is there a specific reason for uint's uncontested ...
7
votes
3answers
4k views
How to get the cost (in gas) of the non-constant function call?
In my understanding, there are some situations, where the compiler can't calculate, how much Gas it takes to complete the function call. The most obvious example - when your function is calling some ...
11
votes
2answers
7k views
Local variable and state variable, and the difference between them
I am new to solidity. When I read the solidity documentation, it says local variable and state variable. But I can't find the definition of the two terms.
Can anyone explain the meaning of local ...
0
votes
0answers
624 views
totalSupply in ERC20Basic contract is not initialized to zero. Does that matter?
I copied code from TenX, which copied code from OpenZeppelin.
TenX and OpenZeppelin has this code for contract ERC20Basic:
contract ERC20Basic {
uint256 public totalSupply;
function balanceOf(...
2
votes
1answer
511 views
Local storage variable
I am reading the solidity docs here and I seem to be struggling to understand the
following.
Data locations are important because they change how assignments
behave: assignments between ...
1
vote
0answers
70 views
Layout of State Variables in Storage -> specifically NON Statically-sized variables e.g. Mapping
The following page provides information on how to access a contract's state variables, regardless of who the owner is or what methods are exposed.
http://solidity.readthedocs.io/en/latest/...
1
vote
1answer
139 views
Function doesn't change change variable's value
I have made a contract with a struct, Stock. I have an array with two such Stocks. They can be initialized fine, but when I try to change the value of a variable nothing happens. Also, the same ...
1
vote
2answers
170 views
Not able to read data from smart contracts
I am doing PoC on Ethereum using Azure Ethereum network and Web3. I was working from last 1 month and I have created one smart contract for student management and that was working like fab. But for ...
