Questions tagged [dapps]

Questions about applications and projects on Ethereum: a decentralized application (dapp) does not require any servers or backends and runs independent on a distributed blockchain.

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How to get transaction Status and data regarding that transaction in web3js?

I have a Dapp where user can buy and send ERC20 token whose bussiness login written in Smart contract..Now when someone buy the token, how do I know in web3 that how much token they've bought and what ...
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14 views

Events not working in Trust wallet or Metamask

Recently, I've developed an Dapp using pure vanilla js and it's contract is currently deployed on etherscan.When someone buys a token, it should increment..Everything's working fine but in the trust ...
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13 views

how to use custom web3 provider for Dapp?

I used to use metamask for Dapp development..Everything works fine, but trust wallet(Dapp mobile browser) doesn't emit events comes of from contract..My Dapp is heavily rely on events..if they don't ...
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9 views

Neither Token name nor supply shown in etherscan, instead shown “() N/A”

Recently, I've created an ERC20 token on Etherscan and verify the source code but my token information such as token name and total supply not showing up..Instead it shows balance: 0 N/a and supply ...
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transact to Auction.placeBid errored: VM error: revert. revert The transaction has been reverted to the initial state

I signed up for a "introduction to Blockchain" course in my exchange semester in South Korea and I feel like it's not just an introduction because for half of the final grade we get we have ...
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19 views

Import error for openzeppelin

I have tried both pragma solidity ^0.5.0; import "openzeppelin/contracts/math/Math.sol"; pragma solidity ^0.5.0; import "@openzeppelin/contracts/math/Math.sol"; Getting an ...
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1answer
12 views

Getting 0 holder on Etherscan testnet despite having token transactions through DAPP

Recently, I've created a token and it is pure ERC-20 Compliant...I've sent some token to another address but when I see it on rinkeby testnet etherscan web page it shows 0 holder despite having the ...
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18 views

How to Host and deploy DAPP? [closed]

I have made DAPP successfully using Solidity as a primary backend language and HTML for frontend.. Now I want to deploy it. So anyone can access it permanently all over the world..But I can't able to ...
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18 views

Time-dependent test unexpected behavior at 1st attempt, expected behavior at 2nd attempt

I'm trying to test a contract in which functions should require certain timestamps. Parts of code are eliminated for readability: Here's the problematic part of the contract : PCE_Contract.sol pragma ...
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23 views

why does ERC20 Token Balance shows 0 frequently?

I have a DAPP and ERC20 Token which has an initial supply of 9000 for testing purpose..First step is to login/register into the DAPP where all the information resides..There is an element in the DAPP ...
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37 views

Need only sign transaction feature (not send transaction)

I am developing an online store BNB as a payment. Customers will sign transactions using Metamask and then frontend code(js) need to post call to our backend server with the txHash, and then we will ...
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22 views

Uncaught (in promise) TypeError: Cannot read property 'deployed' of undefined

I am working on a truffle dapp project. Other than init(), initWeb3(), and initContract(), I have been doing fine interacting with my contracts in several JavaScript functions, until I created my 9th ...
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Why do I get big number occasionally wherever I call Smart Contract functions using web3js?

I have column named total balance, which has a type of uint and function named getBalance which return its balance and the corresponding functionality has been also declared in Web3js..They get called ...
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24 views

How to calculate the ERC20 token price with respective to cents?

Initially, I have a ERC20 token price as 10 cents.. so,to sum it up. 1 token = 10 cents 10 tokens = 100 cents/1 dollar and so on...! How to use cents in Wei form in solidity to calculate the token ...
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22 views

web3.js convert hex value to string [duplicate]

I use web3.js to read all events and I get the return values when convert this field to original string (string indexed name) original name like mmmm the hex retrund is ("...
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25 views

Require not working properly, always lead to an error

There is a login page and register page in my dapp based on refer and earn concept to authenticate and authorize user respectively..Login part is working fine, but when I try to register a new account ...
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How to detect public address with web3 py on dapp level?

Let's say I deploy a voting app with web3py as the backend. Now an arbitrary user wants to cast a vote. Given that web3py cannot be integrated with metamask, what is the conventional way to detect the ...
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19 views

Listen to latest event emitted by smart contract with web3j API in JAVA

I'm having a smart contract: pragma solidity ^0.4.21; contract NodeServie{ event triggerEvent(address indexed _sender, string randomStr); function callEventFunc(string str) public{ ...
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35 views

Must I add WETH conversion descritpion in a contract and how?

I'm confused about how I write a contract about WETH conversion. When we write a smartcontract depositing user funds into a contract, should we necessarily write some codes of converting eth into weth ...
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1answer
48 views

What happens if someone DOS's my infura api link?

I have an infura link, and put it on my frontend as the default provider url. What happens if someone DOS's that link and uses up the daily api request limit? It's unclear how infura protects against ...
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1answer
35 views

this error while sending transaction using infura.io . The method eth_sendTransaction does not exist/is not available,

My ERC20 token dapp is giving an error only while using 'transfer function' even when I am using a given address as defaultaccount ( otherwise the error was "No "from" address specified ...
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1answer
25 views

Sending ether directly from metamask to fallback function

I want to send some amount of ether to a smart contract from metamask (without using web3) and want it to perform some specific tasks based on that amount. For example, if I send 0.9 ether, I want it ...
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2answers
30 views

Unhandled Rejection (TypeError): this.web3.eth is undefined

My getWeb3.js file: import Web3 from 'web3' export default async () => { var web3Provider = null; if (typeof window.ethereum !== "undefined") { web3 = new Web3(window....
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23 views

How do I verify a contract that has imports on etherscan?

There is an answer from 2017 here saying that it's not possible but it's been 3 years since then so hopefully there is progress. My Vyper contract looks something like this: import ERC20 as ERC20 ...
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29 views

How do I get the decimals of an erc20 contract when the decimals variable is not there?

What is the best practice for doing this? In the ERC20 standard having a public decimals: uint256 is marked as optional. But obviously you cannot display a token balance in the UI without having the ...
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1answer
24 views

Metamask Wallet Change in Dapp

I wonder something about the usage of the metamask wallet for Dapp. I have implemented an Authentication mechanism to my Dapp with Keycloak, and I ask for blockchain wallet addresses of the users in ...
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1answer
11 views

How do you handle a chain re-org with contract events?

Given that events are fired whenever a transaction is included in a newly mined block, how do you handle the situation when the mined block containing the transaction gets orphaned? Say I have a ...
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1answer
18 views

What are the required platform to make mobile app that has dapp features?

I recently went over dapp with ethereum block chain but most of the coureses and documentation follows example in webApps. I want to know what are the possible frameworks/library, technology/ ...
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43 views

How do I send multiple transactions as one transaction?

Say I need a user to approve a contract with an erc20 token balance and then the contract can execute it's function after. Typically, I would have to do an approve transaction with a nonce of 1 and ...
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1answer
12 views

Need of writing tests again and again

I started learning about ethereum and dapps just a week ago.I totally understand the need and importance of writing tests for an ethereum smart contract. But what I didn't understand is that I already ...
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1answer
20 views

Need Some Basic Information related Ethereum [closed]

I'm newbie to block chaining and need help related truffle and related tools.... Q. Whats difference between truffle and ganache? Q1. Is truffle/Ganache(Don't know difference) is server side EVM, I ...
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57 views

Minereum Lucky Draw claims 100% Safe randomness on a smart contract without oracles, is it really possible? [duplicate]

Is the way Minereum Lucky Draw game works really safe 100% onchain RNG and verifiable on smart contract? They claim yes but I would like to know expert technical answer for this, if so, isn't this a ...
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Defining an endpoint dinamically in metamask?

I am creating a permissioned ethereum blockchain network and many dapps will be deployed in it. Since the dapps need to check some rules before submitting transactions to the node (yes, it is a ...
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1answer
36 views

How to implement recurrent smart contract without third-party libraries? [closed]

I want to implement an investment service based on ethereum smart contracts in which customers receive dividends four times in a month. For example, a customer receives dividends on 8th, 16th, 21th, ...
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32 views

Rock, paper, scissors and Secrether.io

I have thought of a RPS game using secrether.io: playerA hashes keccak256(move+11charsRandomData) as hash and sends it to RPS smart contract. RPS creates a transaction to Secrether Smart Contract - ...
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8 views

How to show token balance from a ETH address in my Android App?

I have an Android App and I want to show the balance of an especific token of the user wallet Address IE: show how many CHAINLINK are holding the user on his wallet Thanks in advance
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23 views

Where does DappNode ubuntu installer download the .ethereum files?

I am currently using DappNode and syncing the blockchain. When I used GETH directly there used to be .ethereum folder where all the chaindata and keystore was present. But when I use DAPPNODE the ....
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21 views

Negative integer function

I have the following problem, one of my function has a variable where the uint can be negative but I don't know of that before the user enter in the form the integer. How do I settle this problem ? ...
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1answer
25 views

Is there any advantage of using localhost as testnet in Metamask?

I am using Metamask with ganache to deploy my Dapp, i use localhost testnet depend on some tutorials i followed it but really i don't know if it has any advantages comparing with other testnets or no? ...
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1answer
27 views

call a contract function which creates a new contract in web3.js makes an error VM Exception while processing transaction: revert

At first I'm developing with truffle v5.1.34, Node v10.16.0, Web3 v1.2.4 To make it simple, I have a Two contracts, DApp and User What i'm doing is call a DApp contract function which creates a new ...
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1answer
37 views

DApp Development- how to update dapp and keep existing data

Compare to web application that separate the application and database, we can update the application and keep the existing data. Could you suggest me how to update dapp and keep the existing data?
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31 views

Is it feasible to write a DApp that targets multiple blockchains

This question does not target Ethereum specifically, but I hope you can help me out! If my questions are too specific, I apologize in advance. I'm trying to utilize Blockchain's immutable + provable ...
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28 views

Could not Able to start my genesis block “Fatal: Account unlock with HTTP access is forbidden!”

I am getting some problem while i am trying to mine for my genesis block on my Geth command prompt "Fatal: Account unlock with HTTP access is forbidden!" could anyone please provide me help ...
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2answers
49 views

Generating random number in Solidity without Chainlink

Hello I'm well aware there are plenty of threads around discussing different methods. Just curious and wanted to ask directly here because feel like the situation might be different. Essentially I'm ...
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1answer
32 views

Web3 js and frontend frameworks [closed]

Will i need a front end framework like React, while using web3 to build Decentralized Applications?
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41 views

Cold wallets & dapps

I am new to ethereum and curious about interacting with dApps while keeping a private key in cold storage. I like the idea of keeping the private key for an Ethereum wallet on an air-gapped computer. ...
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1answer
51 views

how create address for each ethereum user [duplicate]

I have a group of Ethereum users how do I create an address for each user to send their data on the network?? I want a way to create addresses for each user??
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1answer
56 views

how different users write their data in ethereum network?

How a number of blockchain users save their data in the blockchain network using ethereum. Meaning more than one user sends his data using Python to save it in blockchain networl ?? How do I ...
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1answer
32 views

Solution for mapping corporative credentials with Ethereum account [closed]

I need a solution for mapping corporative credentials (like Active Directory) to users of a "corporative Ethereum account". In other words, all users of the company may use the same Ethereum ...
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1answer
99 views

Compilation Error

Hi guys I got this error when I try to compile using truffle develop. truffle(develop)> compile Compiling your contracts... Compiling ./contracts/StarNotary.sol /mnt/d/Blockchain/...

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