Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
0answers
9 views

Create Dapp with multiple web page [on hold]

I have created a Dapp where one person will to a transaction and it will log all the events. I want 2 pages for this one for transaction and one for dashboard where every transaction can be monitor. ...
1
vote
2answers
16 views

How to use fiat exchange rate oracle in DAPP?

my team is trying to develop a DAPP about fiat exchange rate. How to get the latest fiat exchange rate (USD/EURO etc.) accurately from external Oracles(Or are there better ways doing this)?
0
votes
2answers
23 views

How to decode data parameter under logs in transaction receipt?

I went through many questions but I couldn't get my answer. web3 version -- 0.20.6 According to documentation event's parameters which are not indexed store in data parameter under logs. I want to ...
1
vote
3answers
52 views

Get rid of Metamask sign confirmation dialog

I am using web3 for users to sign some random string from web application. I give user string, he/she signs it after Metamask dialog's "Sign" button. but there is a problem when i want user to sign ...
1
vote
1answer
25 views

Why no dapps in the Google Play Store? Why Ethereum not accessible by default in smartphone?

Before I create a decentralized application, I want to know whether it already exists. I thought the first step would be to search the Google Play Store, but it appears dapps are not available on the ...
0
votes
1answer
31 views

getting error nonce too low , but nonce is proper stuck since one day

I am working with web3.js since sometime now , but now i am stuck with nonce too low error , the nonce is proper also i have checked private key and other addresses , they also seem to proper , ...
0
votes
2answers
41 views

How to sign a transaction automatically?

An api will call the smart contract function. It should sign the transaction on its own instead of human intervention. I think raw transaction can work here. Are there any other options? Any help is ...
0
votes
1answer
15 views

Store a registry of students [closed]

I'm currently developing a dapp related to student registration. There is a large number of students and I suppose that the best way to keep the registry is not in the smart contract(ex: as a mapping) ...
-4
votes
0answers
20 views

How blockchain election dapps work? [closed]

How blockchain election apps work? How can auditing team check the real numbers of votes for specficCandidate? And how it work in technical (coding) way?
2
votes
1answer
24 views

How to transfer eth to a solidity function from a Dapp

I am trying to build a Dapp which includes functionality to deposit funds to a contract and withdraw them. The functions look like this function fundContract() public payable { require (msg....
0
votes
0answers
20 views

Infura API for mobile(ionic) app

I have one little question. Suppose I have private key of user in ionic app. Is this enough to make transactions using infura API and web3?
2
votes
1answer
37 views

Login system for DAPP without metamask

I'm building Dapp on Ethereum. Imagine I have companies to register in my dapp, I will provide them with their own smart contract and public and private key pair, which they will use to just unlock ...
0
votes
3answers
55 views

Login system for DAPP

I'm building Dapp on Ethereum. The main feature of this Dapp is Register/Login logic. I Don't want to use Metamask, but I want to make Login system like MyEtherWallet without any chrome extention. ...
2
votes
2answers
26 views

using Ethereum without any gas or coins usage for transactions

I am new to Ethereum. We are planning to use Ethereum for building an application where-in we don't want the users to buy and use Ether's. We want the user's to safely store and retrieve / share the ...
0
votes
1answer
14 views

How to evaluate effectiveness of a Dapp

I am developing a private ethereum-based DApp and writing an academic paper for a final year project. I'm trying to "blockchainify" an existing system that adopts a traditional client-server approach. ...
1
vote
1answer
45 views

How to access metamask accounts when using Infura Websockets

I am making a dApp where in for login purpose I access metamask account to which user is logged in. I also have a back end server that listens to events emitted by the smart contract that updates data ...
1
vote
1answer
34 views

Solidity event listener

This web3js event listener is part of a Voting Dapp. The listener listens for a transactions and re-renders the page to show updates. listenForEvents: function() { App.contracts.Election.deployed()....
1
vote
0answers
38 views

web3.personal.newAccount() successfully created but not listed in ganache accounts.why?

I am using truffle framework for Dapp development and I am new in Blockchain.I used the command web3.personal.newAccount() to create a new account. But i cannot view this account when i take ...
1
vote
0answers
8 views

In windows, what do I type in powershell to connect my dApp to a liteserver? [closed]

In windows powershell, what do I type to connect metamask to a liteserver? >
1
vote
0answers
18 views

Is it possible to deploy Dapp on Etherium classic network and be listed in mist?

So as a small bisness entety can not pay 100k USD for app deployment, one wonders on is it possible to deploy Dapp not in the test net but in a more real ETC one?
1
vote
1answer
25 views

Solidity cross programming language method calling

I was wondering if it is possible for solidity to call functions of other languages. More specifically, I am planning on developing a basic distributed search engine using the ethereum blockchain and ...
1
vote
1answer
48 views

Storing Non-Transaction data on Private(or Public) Blockchain

I'm fairly new to blockchain technology and need some advice for my first application. I'm creating a dApp for Asset Tracking using a private ethereum blockchain network. I have already created the ...
0
votes
1answer
16 views

How to catch Out of Gas exception in Oraclize Callback and display error on dapp front end

I have a smart contract inside which I have used Oraclize to get current time stamp. On few occasions the Oraclize callback fails due to out of Gas exception. How can one catch this failure and ...
0
votes
1answer
21 views

Is it safe to have a locally running Ethereum node exposing personal RPC API?

I am developing a REST API currently running off a node.js server. The API allows ethereum account creation, making a transaction etc. The API interacts with a locally running ethereum node to ...
1
vote
1answer
22 views

How does smart contract work in network

I have read a lot about smart contracts and also have seen lots of implementation tutorials. But there are some ambiguous points in it that I can’t investigate it completely. For example: Imagine we ...
1
vote
2answers
49 views

MetaMask Web3 object does not support synchronous methods without a callback parameter [duplicate]

I'm new around here and would appreciate some intuitive help. I wrote a contract and made a UI for it, and it's all working fine with ganache-cli. However, now that I've launched it on Ropsten and on ...
1
vote
1answer
42 views

Not sent by ETN via transfer

I'm trying to make a lottery. pragma solidity ^0.4.23; contract Lottery { struct Ticket { uint id; address name; uint winCount; } uint public winFirstPercent = 60; uint public ...
1
vote
1answer
35 views

How to get notify if transaction got failed, dropped, or successes [closed]

I am new in dapps world and I want to deduct balance/points when a user buys an item currently I am unable to update balance because sometimes transaction got failed, dropped, or successes after 30 ...
0
votes
0answers
22 views

Dapp design to handle delay in callback response from Oraclize

In my dapp design I am receiving few user inputs via a form and passing them to a smart contract. Inside the smart contract I am using Oraclize service to timestamp the user inputs. Its a known fact ...
0
votes
0answers
31 views

How do DApps that don't need their users to run Ethereum nodes or Metamask work?

For example, A website which will give the option to register an ethereum account. The user would hit the register button and the server, which I assume is running a node 24/7 and will generate an ...
0
votes
0answers
28 views

Dapp new user accounts in ethereum

I create dapp with the ability to register users. I have no ideas on how to do so that the registering user could create a new account in the ethereum network. If I connect to the main network using ...
1
vote
0answers
19 views

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 ...
1
vote
1answer
24 views

Smart Contract Balance = 0

Ok, I am pretty new to developing contracts, and I did so by using dAPP and truffle. But when adding it to the chain, it says there is no balance to the contract. How can I add tokens to be bought? ...
0
votes
2answers
45 views

Is ERC721 an appropriate standard for managing licenses?

In my example scenario, I have an e-commerce dApp where e-books are sold. I originally thought that I could represent licenses to access these books using non-fungible tokens (NFTs) through the ERC721 ...
0
votes
2answers
44 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 ...
0
votes
2answers
38 views

ERC721 Dapp not working, not showing token owner

So I am building a Dapp to interact with an ERC721 contract. So far I'm able to mint, transfer and check an address balance. I'm stuck with trying to show who owns which token( via their token id). ...
1
vote
1answer
21 views

Double voting unit test failing on Election dApp

I am working through DApp University's election dApp tutorial. I made unit tests for invalid candidate, and double voting. My double voting unit test is failing, saying: 1) Contract: Election ...
0
votes
0answers
23 views

How to make data public on dapp

Trying to make a DApp website with solidity (Just learning for fun). Was able to create a simple DApp website but the data is only visible for me only. How do you create a DApp where users can see ...
0
votes
1answer
43 views

One IDE for running a DApp

Is there one IDE that can be used to run a DApp ? I have the backend (solidity) and trying to build the front-end for it.(So the IDE should help me to build the front-end side as well as run the ...
0
votes
0answers
12 views

How to create periodical token minting with randomness?

The Problem: I need to create a contract that will automatically mint tokens with some kind of randomness. For example, mint up to 5 tokens every window of 30-50 blocks: block #100 - contract ...
0
votes
1answer
25 views

Is it possible to check a token transaction history for an account with web3js?

If I have an account that has sent and received specific tokens, say ExampleToken (EXT), can I use web3js to see a list of EXT transfers and receipts for my address (or any other address)? I am ...
0
votes
1answer
57 views

How to get only past 2 days events using getPastEvents everytime?

How can the following query be modified to only fetch the past two days worth of events: const events= await MyContract.getPastEvents("eventName", { fromBlock: 0, toBlock: "latest" });
0
votes
1answer
80 views

List ERC721 tokens owned by a user on a web page

Let's say that I have an ERC721 (NFT) contract that represents a set of playing cards. Is there sample code out there that shows listing all of the tokens of that ERC721 contract that a user owns on ...
1
vote
3answers
156 views

Why would I use Metamask instead of only using Web3.js in the browser?

It is my understanding that Metamask brings a convenient way for the user to interact with DApps by storing their wallets and by providing an interface that gives the user control of what the DApp is ...
0
votes
2answers
110 views

MetaMask verification on a server with web3.personal.sign

How to verify MetaMask account holder is the real owner of the address? I recently saw this post and tried it immediately, unfortunately, I am not getting the right result from the server. I think it ...
1
vote
0answers
27 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 = ...
1
vote
0answers
88 views

Calling function from another contract reverts

I've been developing a dApp that needs ERC721 tokens. I have three contracts, a base contract, the one to mint tokens and another one for auctions. The inheritance looks like Base > Token > Auctions. ...
0
votes
1answer
23 views

Search Struct or Mapping with minimum gas

I am trying to create a proof of existence dapp using IPFS and Solidity and wish to implement a feature to add 'tags' (like we attach to question on stack overflow) to each file/document uploaded on ...
0
votes
1answer
25 views

Checking if Contract Withdrawal Is Allowed

I am trying to conceptualization how a specific kind of smart contract would be written. The contract would basically handle deposits and withdrawals of ETH or some sort of ERC20 token. The balances ...
0
votes
1answer
60 views

Solidity - Shuffle address[] Index

Hello World ! I'm trying to find a way to shuffle an array of addresses in Solidity ! Looking at Underscore / Lodash source code _.shuffle() points out a few things. _.shuffle([1, 2, 3, 4]); * // ...