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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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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269 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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126 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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68 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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31 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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154 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
1k 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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132 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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401 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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276 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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547 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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78 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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186 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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685 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
320 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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1answer
15 views

How to call a write function of contract from Dapp?

I have created a smart contract in which a "stop()" function should be called once a deadline is reached. Dapp is keeping check of the deadline and as soon as the deadline is reached I need to call ...
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1answer
21 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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33 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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29 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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25 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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21 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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24 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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16 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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18 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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44 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
22 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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79 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
27 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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59 views

Getting Metamask Error Message into web3.js DApp after user rejects transaction

I'm building a simple HTML/JavaScript front-end to interact with a Smart Contract using web3.js and MetaMask. I have a function to call one of the methods in order to send a contribution to the Smart ...
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1answer
30 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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31 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
19 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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11 views

Prompt Metamask to send eth with Web3

I understand this as the pattern to send a transaction with web3: web3.eth.sendTransaction({ from: myaddress, to: toaddress, data: web3.eth.abi.encodeFunctionSignature('whitdrawETH()') ...
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1answer
23 views

Is it possible to instantiate a deployed contract in js using contract address alone? without copying abi data?

Is it possible to instantiate a deployed contract in js(dapp) using contract address alone? without copying abi data?
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2answers
45 views

do users should be aware of smart contract of the dApp they are using?

So dApps are frontend + contract. Users interact with smart contracts via frontend. Do users i.e. people should be aware of how the contract is designed while using any dApp? are their any risks of ...
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33 views

Error using drizzle and react

My contract Storage.sol - pragma solidity ^0.5.0; contract Storage { string public data; function getData() view external returns(string memory) { return data; } function setData(...
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297 views

web3.eth.getAccounts() returns empty array

I'm trying to get accounts like that: window.web3.eth.getAccounts( (error, accounts) => { console.log(accounts, error) } ); but it keeps returning an empty array. I'm running Ganache and I can ...
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28 views

How to use the ipfs.get()?

I am new to IPFS. I added a file in IPFS and then, pinned it. Now, I am trying to retrieve the file. I am writing the code in React. Hence I used the following code: ipfs.get('/ipfs/...
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1answer
64 views

getWeb3ClientVersion() returns null

I'm trying to create an android Dapp by using the web3j library. I'm using connection to a local private Ethereum blockchain. When I'm trying to display the Client version it returns null. This is the ...
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40 views

Hosting pet-shop DApp on IPFS - JSON Files problem

I am trying to host DApp "pet-shop" which one of the truffle boxes on IPFS. rsyncing of src, build/contracts and ipfs add files went very well and there are plenty of peers as seeders on the network ...
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1answer
18 views

can't get struct in return

I am trying to execute unit tests for a solidity smart contract: I have: mapping (bytes16=>Device) public Device_Table struct Device { bytes16 UUID; bytes16 hardware_UUID; string ...
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42 views

How to filter MyEvent({ },{ }) to retrieve only the latest transaction in the array?

My code: instance.MyEvent({}, {fromBlock: 0, toBlock: 'latest'}).watch(function(error, event) { if (!error) { console.log(event); $('#events').html(event.transactionHash); } else { ...
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46 views

Timestamp is giving wrong time in smart contract

Today is June 17. but when I execute my function and store the following arguments. WriterModel(owner,postID, _postContent, now); "now", It returns the July 20 timestamp. It perfectly working fine ...