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 can I make an API that can receive a transaction hash and return the transaction result?

I have a simple gaming contract where users play dice and bet on the result giving the range (1-100) in which the two dice rolls might result to. It has a payable function called call_bet( ) which ...
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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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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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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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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
30 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
19 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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21 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
46 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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48 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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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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Uniswap V2 smart contract keeps getting reverted in JS

I'm trying to swap tokens using Uniswap v2 interface. The code of the contract is here. I'm able to deposit Eth to the contract and but I'm not able to invoke the swapEthForTokenWithUniswap() ...
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31 views

Data validation using Ethereum

I'm pretty new to the BC and specifically Ethereum world and I'm just starting to scratch the surface of the potential applications of this powerful technology. As I'm approaching to build my first ...
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Truffle + Infura Mainnet deploy. Transactions never get mined, timing out after 750 seconds

The contract deploys on Rinkeby without a hitch, but when it comes to mainnet it is erroring out strangely. Infura's HTTP endpoint was giving me Invalid JSON RPC RESPONSE "", so I decided to ...
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Ether transaction does not reflect in ganache

Hi am developing a etherium DAPP. In that for every user registration some ether will get transfer from user to contract... Everything work perfect but the transacted ether is not reflecting in ...
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contract.deployed() not working when trying to submit an html form

i am using web3.js to communicate with my smart contract. how ever, when i try to submit the html form, and then use contract.deployed(), it isnt working below is the code.Html <div id ="input" ...
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Any good recommendations on online courses for learning how to build decentralized apps?

There's one called DappUniversity, but wondering if there are any other courses. And where did you learn how to build dapps? Thank you!
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why can't we get the meta mask injected account using web3.py? [duplicate]

I am trying to get the current account from meta mask in my Dapp ,i am using web3.py. In web3.js ,web3.eth.getCoinbase() returns the current account of the metamask, but web3.eth.coinbasein web3.py ...
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1answer
23 views

Automate faucet Ether request to access Ethereum Testnet from a mobile DApp

I want to develop a mobile DApp to interact with a smart contract deployed in a testnet (free of charges). The mobile DApp is designated for public users. The DApp needs first to setup a local wallet ...
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What is a good wallet service for iOS applications

I am building an iOS app that rewards users with crypto tokens, just like Brave's BAT or Reddit's community points. I am trying to find a wallet service that I can integrate with my iOS app for users ...
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Unknown Accounts suddenly appearing in MetaMask wallet…?

My MetaMask wallet has multiple accounts which I did not create. I have no idea how they there. Is my MetaMask wallet compromised? Or is this normal that MetaMask creates new wallet addresses when ...
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1answer
33 views

What you mean by Off-Chain in Ethereum Blockchain? can i use geth as off-chain in DApp?

I have read several articles of off-chain definition and come to know that they are use for scale the ethereum blockchain. but my question is what is actually mean by off-chain word in ethereum ...
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vyper no mappings allowed when adding a function to initialize a struct that has a map inside

Version Information vyper Version (output of vyper --version): 0.1.0b17+commit.eaa6754 OS: Debian GNU/Linux 10 (buster) Python Version - 3.6.2 Environment (output of pip freeze): asttokens==2.0.3 ...
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20 views

Modifier accessing another smart contract function

I am trying to use a modifier that calls a function from another smart contract to check the type of user that is accessing the function. The user should only be allowed to access the function if ...
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2answers
56 views

Building a mobile DApp without a full node?

I'm new to blockchain and Ethereum and have a few questions: Does Apple's App Store allow mobile DApps other than wallets and browsers? Is it possible to build a mobile DApp that runs on your mobile ...
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33 views

Certificate Autority to Ethereum

Since there is no native support to Certificate Authorities in Ethereum, what are good ways to emulate it in a permission network (we are using Hyperledger Besu)?
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Best way to avoid transactions that create a new smart contract before submitting it

We are creating a permissioned network (using Besu) where anyone can create and submit transactions. In this context, the writer nodes need to verify that these transactions are not creating new ...
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29 views

How can I test someone else‘s ETH contract with only bytecode and ABI? [duplicate]

If I just have someone else's ETH contract bytecod an ABI, how can I test it's function?
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0answers
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Possibilities of ERC721 image generation [closed]

What image generation techniques could you suggest for a DApp game that utilizes ERC721? I know that CrypoKitties has a unique DNA sequence and different pieces of the sequence correspond to the ...
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6 views

User Profile with access control to allow other users to edit information [duplicate]

Sorry if this has already been asked but ive been searching for days and cant find an answer to my question. I want to create a dapp that allows users to sign up and create a profile with private ...
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1answer
30 views

How to search for a dapp based on its address?

There are many websites that track dapps like http://dappradar.com or https://www.dapp.com. Unlike Etherscan one particular dapp doesn’t have to be registered on such specific website in order to be ...
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28 views

ERC20 Anyone can call approve if knows ABI on contract and my address?

I think I misunderstand something. I'm using a Ganache for developing dApp. I built a default ERC-20 smart-contract. I've built it with truffle. And just for test I write some code in NodeJS: ...
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I need help with ERC-777 usage possibilities of extra funcionality layer over ERC-20 for non-coder

Im interested in creating custom token (fungible), but with gas-less operations possibilities for V.I.P. customers. I need simple app (wallet is fine) which would: allow me to store custom ERC777-...
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1answer
38 views

Can an Ethereum account be used by several users at the same time?

I am developing a DApp for donations (the donations are not in cryptocurrencies). I want the donor to make donations without registering on the platform. In fact, I don't need to know who he is. So it ...
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1answer
22 views

How can conditional deployment of a contract be done? [closed]

This might be a very basic query, but, I would like to know how I can restrict the deployment of contracts based on some condition. More specifically, assume that I have an "Admin" who can assign "...
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23 views

Just not able to install Web3 through powershell

After reading a lot of articles about how to install Web3j in windows. I also tried following this article : https://kauri.io/generate-a-java-wrapper-from-your-smart-contract/...
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1answer
19 views

Web3 call should return different result based on time passed

I am experiencing a weird issue. I am building a DApp where I want the new season of the game to start every 5 minutes (for testing purposes). However, web3 call returns old data, seems that it cached ...
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2answers
31 views

how i can create a buy Ehter [closed]

i have a question : how i can create a app to buy ether ?, i know how to create a Token sale but i dont know what api or what i need to buy ether directly i see websites like coinbase to buy ether , ...
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27 views

Trying to connect Ethereum Wallet with ganache-cli on Windows

I am trying to connect Ethereum Wallet with Ganache-Cli but it starts looking for geth note instead of ganache-cli. Can someone please tell me the correct way of doing it. Or is there any specific ...
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1answer
134 views

Provable API for calling ETH-USD price in a contract

This contract is hosted at https://github.com/provable-things/ethereum-examples/blob/master/solidity/truffle-examples/kraken-price-ticker/contracts/KrakenPriceTicker.sol I have made the constructor ...
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13 views

setBill function isnt affecting the values

a beginner contract developer here pragma solidity ^0.5.0; contract waterBill{ address admin; uint public rateperliter; struct Individual{ string name; string addr; ...
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43 views

what is the best to signing a message , from javascript or solidity?

I am trying to make a small DApp using web3, ganache, Metamask, javascript and Remix. My DApp has to sign a message and verify it, and I see two ways to sign a message. One using web3.eth.sign(...), ...
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53 views

window.ethereum

When i made web3 instance and run index.html i lose ethereum and window.ethereum when i call it from console i got ethereum is not defined,i have installed metamask and use ropsten network.Why its ...
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1answer
25 views

Uncaught TypeError: Cannot read property 'fromWei' of undefined, working good in one tab and failing in another tab

I'm getting this error when I'm trying to convert Wei to Ether using the code window.web3.utils.fromWei("200000",'ether'). This error shows only on the single page and when I console.log in the same ...
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24 views

Metamask and Web3

I use this in html src="https://cdn.jsdelivr.net/npm/web3@1.2.6/dist/web3.min.js" and when i call some functions i get error.Why this happend?Example i cannot call ethereum.enable() for allow ...
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1answer
29 views

How to find the source code of my contract which is not yet verified

I had created a token using eth based blockchain via remix.ethereum.org But I need to verify the source code ,but I am not having the backup copy of source code How can I see the source code of the ...
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1answer
33 views

Creating complex queries from events emitted by a smart contract

I need to create complex queries from events emitted by a smart contract. For example, I need to make a kind of "sql join" between data from different events. I know a simple solution would be to ...
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2answers
26 views

How can I change the state of a contract if it's stored on the blockchain

Doesn't that contradicts the whole idea of blockchain that data stored there is immutable. If someone can alter the data stored in the state of the contract then how is it any different from any other ...
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36 views

Ethereum DApp example? [closed]

I am finding for the open source ethereum dapp example. Could anyone recommend me any dapp that is fully operable by my own? Thanks.

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