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.

178 questions with no upvoted or accepted answers
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trading a secret message with some person only after money is paid

I want to build a DAPP where person A trades a message with person B for ether. Since the message is secret, person A encrypts the message by using public key of person B and stores the message in ...
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63 views

import packages in petdapp

I unboxed petdapp and done some editing where I need to import bcrypt-nodejs in app.js and used following steps. npm install bcrypt-nodejs --save npm install require --save app.js var bcrypt = ...
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1answer
59 views

MetaMask transaction popup opens on another computer

We have two computers on the same local network with Static IP for internet. When Computer A calls a transaction through a DApp for an address X, Computer B Metamask is also getting triggered with the ...
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23 views

Augur Project compile and debug

I starting to work on blockchain and dapps, would like to help with issues in augur can anyone explain how to debug or test run the application on my local machine to know how it works? i tried to use ...
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1answer
376 views

Is it possible to send ERC20 tokens to a smart contract that is written to accept payments..?

I have ERC20 compatible token that is already deployed in the ethereum main-net. I have a requirement to accept these tokens as payment, And this is going to be a new contract, The below are my doubts....
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280 views

Paying for gas on behalf of users?

I'm exploring ways to enable contracts/dApp owners to pay for gas on behalf of users. I know contact abstraction should enable this eventually, and the first step has been done with EIP208 which ...
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127 views

Toshi browser vs. Google Chrome browser to interact with Dapp?

Toshi is a browser to interact with Dapps such that after uploading our Dapp (including solidity smart contract, Javascript and HTML code) on a server, we can search our Dapp using its URL (ex: www....
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71 views

Distribution Contract Not Working

I'm trying to set up a distribution contract to send an ERC20 token to multiple addresses at the same time. After multiple attempts, the transfer keeps failing. Transactions are approved, the problem ...
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33 views

Keeping Contract Address, Web3 HttpProvider and Account Address away from the DApp UI/Frontend User

I am building with Quorum and Web3js. As I build the DApp UI/frontend, I realised that details such as address of the node, contract address and the account address (from:) are in plain text. One just ...
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147 views

how distributed cloud storage works with ethereum blockchain?

Distributed Cloud storage is a great concept , I have been doing a lot of search on this topic but couldn't get the exact information i am looking for:- How the projects like Storj are using the ...
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158 views

Can't transfer balance from contract to parent contract

I'm having trouble transferring remaining funds from a Contract to it's controlling Contract Factory. I'm trying to do the following. Create a new Service with Factory->createService() Add funds to ...
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1answer
2k views

How do I automatically mint ERC-20 Tokens Every time the owner wallet transfers coins

I want to start with a total_supply of 1,000 Tokens in the owner wallet. Each token will represent a gram of gold. Every time 1 token is transferred from owner wallet to another wallet, the owner ...
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71 views

Blocking an application untill metamask shows the transaction is complete

I’m creating a DAPP where I’m using Metamask for submitting the transaction. I have a requirement where when a user accepts/submits the transaction, a modal needs to appear on the page, blocking the ...
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137 views

Token Contract Created by Factory Contract is not Showing up in metamask

I have a FactoryToken Contract Deployed and its function "newToken" Creates a new token contract. Every thing is working fine on Remix IDE but when i call the FactoryToken's function To create new ...
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406 views

System requirements running blockchain application

From an IT/infrastructure perspective (im not a developer) what are the system requirements to run a fully functioning blockchain application i.e based on ethereum for a small - medium sized business. ...
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1answer
284 views

Watch pending transactions with ethjs.js

I am trying to use ethjs.js to listen to pending transactions, but nothing really worked. Does anyone have a working example fetching pending transactions with ethjs.js? I have tried the following: ...
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559 views

sendRawTransaction fail with “Invalid Sender” on Ropsten but works on Local Node

I have a simple contract deployed successfully to the Ropsten test network using Remix (Verified using https://ropsten.etherscan.io) Same contract has been deployed to my local private node and I ...
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79 views

Will Dapps in production be able to buy and use SaaS solutions?

SaaS services help centralized organizations or apps solve their business problems. For example, Google Apps offers startups as an easy solution for company email and document storage. The sales ...
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1k views

NetworkError when attempting to fetch resource

I'm getting this error in Firefox when running a dApp: Error: NetworkError when attempting to fetch resource. Stack trace: InvalidResponse@http://localhost:8081/bundle.js line 995 > eval:38:16 ...
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135 views

how does a dapp work on mist?

Ive made a dapp work on my system without a geth node working with metamask. The idea is that every user that comes up to the website has to spend his own gas for the transaction, so in metamask a ...
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191 views

Can i post a data to the url in Ethereum smart contract

Actually i want to create a smart contract in ethereum for handling the api requests. creating a proxy kind of contract which makes note of the number of requests in the contract. Is it possible, any ...
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54 views

Ethcore: “The dapp cannot be reached”

On a private dev chain with two Ethcore nodes, I created a dapp as per the instructions at https://github.com/ethcore/parity/wiki/Tutorial-Part-I. Everything was OK and I can see the dapp listed in ...
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2answers
763 views

How to display blockchain transaction receipt details in an Ethereum Dapp

In my dapp design, I wish to provide the user with an option to view Blockchain Transaction Receipt Details either by a link to sites like Etherscan or by providing full details on a separate page in ...
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1answer
326 views

Is it possible to receive text messages (SMS) using ethereum?

Is it possible to build a dapp that can receive sms text messages?
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12 views

window.ethereum: 0 if use MetaMask

I try to connect to MetaMask from my DApp. It used two work well about two month ago, but now window.ethereum object is 0 (not undefined). For some reason ethereum object is 0. I am aware about ...
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1answer
22 views

What does MetaMask mean by stop injecting web3.js?

MetaMask announced that they will stop injecting web3.js here. I know previously MetaMask will add a global variable in browser window.web3 and this global lowercase web3 variable will be deprecated ...
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2answers
20 views

Web3.js eth.subscribe: on('changed', function(event){}) doesn't work with Metamask?

I write a demo DApp website with this javascript const web3 = new Web3(ethereum); const contractAddr = "0x0Aa27e4B13D5c08A8767B36a0ACb76ED4549B7EA"; const abi = ...; let inst = new ...
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10 views

Conditionally Return Content Based On Wallet Tokens

Hi all– new to building dapps. I'm working on a little web game that returns content based on what tokens you hold in your wallet. I'm used to building web apps and mobile apps, but I've never worked ...
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19 views

Using web3.js to interface with smart contract

I am a beginner in Dapp and don't know about web3.js. I complie myslef contracts with Truffle. I did write the following contract: pragma solidity ^0.5.12; contract TEST{ bytes public name="...
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15 views

solidity smart contract thats uses off-chain ML model

I'm new. Hopefully this is an appropriate question for this forum. (This is a simplified example). I want to write a smart contract that receives a loan request, and based on certain features of ...
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1answer
30 views

Sharing an verifiable secret message in a contract

I would like to hear your opinion on my idea to share a proof of a secret message in a contract, that users can verify later in a second phase when the message will be revealed. If the message is a ...
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1answer
48 views

Can I retrieve data from smart contract to my local webpage without using metamask?

I am creating a DApp where I want to show the public variable's information from the contract. I want my users who don't have metamask to see this information also. Is there a way I can do that? If ...
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1answer
22 views

Any issues for web3 on digital ocean?

My dapp which is currently testing on ropsten works perfectly when i run the frontend from local but dosent return addresses when i run on a digital ocean server. it is successfully connected to ...
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1answer
29 views

How do I fix it? To be able to send eth from smartcontract to the address

Frontend class App extends React.Component { state = { address: '', } async componentDidMount() { await window.ethereum.enable() this.w3 = new Web3(window.ethereum) const ...
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57 views

Opera wallet web3 problems

I am writing a Dapp. I'm not an expert. It works perfectly on Edge, Firefox, and Chrome (with MetaMask). But I get the following error on Opera when the cryptowallet is on but not synced: { "error":...
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30 views

What do I have to do to call this events to be display on the web page?

How do I call showLottery to display on my webpage? Front-End class App extends React.Component { state = { address: '', lottery: '', events: '', } async componentDidMount() { ...
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28 views

Automated wealth redistribution

Is the assumption here correct? Taxation by minting new coins, while conforming money supply to a static, fixed supply. The supply of coins is fixed with function supplyRatio() returns(uint) { ...
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23 views

Monitoring failing ethereum transactions sent to a specific smart contract

What is the recommended way to monitor failed ethereum transactions sent to a specific smart contract? Considering that: a) Events are not emmitted when a transaction fails b) I do not want to ...
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19 views

Can a dapp/smart contract execute a transaction based on a private github file modification?

Scenario Suppose someone promises to deliver code to a private repository, that person is so sure they will, that they even said: "here is x eth, if I don't deliver in time, send the x eth to a ...
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27 views

Gas station network use cases

I'm trying to understand the purpose of EIP 1613. Related to this website says "No more Metamask". So it assumes that a user does not have direct access to his private key / wallet. It means the key ...
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18 views

How do a set cookie for a Dapp's front end and pass the information to blockchain?

I am trying to look up documentation on setting up cookies for my dapp using web3 but I am unable to find resources. Can I just use js functions like setCookie and getCookie as one would do for a ...
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21 views

Approving tokens from original contract, how would you do it?

I need to create a general approval for a transferFrom function for an exchange or general contract if you will. I've tried many ways in solidity to reference the old contract, including using tx....
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1answer
13 views

How can I add two plus two on the Ethereum virtual machine

Ethereum is quite different from bitcoin, and in my opinion better. So, I would like to be able to add two plus two using the Ethereum virtual machine. I don’t have any ether, and I’m just curious how ...
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74 views

Issues with metamask in my project

Please look at images: The first images is what i get when logged in to metamask and the second image is what i get when not logged in to metamask When im logged in to metamask i can buy sell ...
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2answers
29 views

validation of data integrity in block

I am learning ethreum dapps development and have developed some dapps. I was thinking about supply chain dapp which i think , is very good application of blockchain as it ensures all the history of a ...
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133 views

web3.exceptions.BadFunctionCallOutput: Could not decode contract function call getEvidence return data b'' for output_types ['string']

Solidity Code: function getEvidence(string memory _evidenceID) view public returns (string memory) { require(evidenceOwner[_evidenceID] == msg.sender); string memory evidenceHash = ...
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1answer
44 views

Contract not deploying with web3

I'm writing a web-based DApp with web3, and am trying to get my JavaScript to deploy a contract. I've set up the abi, contract, and bytecode as follows: const trade_abi = [ ... not shown: ABI copied ...
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1answer
33 views

Why Should I use Ethereum in an Online-Election(Vote) System based on ZKP(Zero-Knowledge Proof)?

I am an undergraduate student studying Ethereum in South Korea. Currently, I am developing an online election system that can be applied. At first, I came up with this idea: The system has an ETC ...
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35 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
22 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 ...