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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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8 views

What I should know in order to make dapp on ethereum blockchain for document verification

What I should know in order to make dapp on ethereum blockchain for document verification … how smartcontract will look like? And how many smartcontract I need? And can you explain me more than once ...
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1answer
12 views

Is there a boilerplate dApp on Github which uses uPort, truffle and infura on the ropsten testnet?

I am developing a dApp using those technologies and facing difficult problems when trying to save information on Ropsten. I can't approve my transaction via uPort because the selected account balance ...
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1answer
11 views

Execution of sending transaction never ends

I send a transaction with web3 1.0.0 from a script like: async function sending(deployed_contract) { await deployed_contract.methods.mymethod(1).send({from: account}) .on('...
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13 views

Transferring ERC20 token using approvals

I have a system where I want a buyer to be able to click on an advertisement (button) relating to a seller which initiates a transfer of tokens from SELLER to BUYER. As this is not a transfer from ...
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1answer
21 views

How to create DApp for Quorum or any blockchain without using web3 and metamask?

I want to create a Dapp for quorum blockchain, the transaction signing via a wallet either in Metamask or pure web3 wallet is an issue and does not work with provateFor transactions in Quorum. So i ...
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2answers
21 views

How To store data in ethereum network using truffle framework ?How to achieve the database layer in dapps?

I am creating a dapp which has to be a login authentication system and some datas has to be store in database. So I really cant' store all the datas in Solidity's variable or class object, it has to ...
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0answers
11 views

Where Does Streamr Market Place Stores Data of Seller [on hold]

In the Streamr Application When a seller creates a product and publish it. What happens next? Where the information about product is stored and when the seller uploads the data stream what happens ...
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0answers
17 views

Questions with Building a dapp using Quorum [on hold]

I am working on a project to build a dapp for a trust system using Quorum, which needs a permissioned blockchain for data privacy. Only the admin, beneficiary, caregivers, case manager and authorized ...
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0answers
27 views

How to implement percentage deposit function to smart contract

I need to implement on the deposit function when the ownerAddress is doing a deposit a 10% to be freeze in the smart contract and and if the ownerAddress want's to call the returnDeposit function by ...
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2answers
54 views

Metamask now longer interacts with PetShop Dapp

Since November the 4th - In order for MetaMask to interact with your webpage dapps, you need to implement the windows.ethereum.enable as part of your scripts I have run through the pet shop tutorial -...
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0answers
14 views

Computer science final year project [closed]

I am a Computer Science major and now I have to make my final year project (FYP). I want to do work in field of block-chain for my FYP. As I am almost layman in block-chain technology. What's your ...
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1answer
13 views

One general contract for all or spawn new one for each instance?

What be the advantages vs. disadvantages or running a general contract or spawning a new one for each instance. Let say, that I am providing a contract so people can create their own crowdfunding. ...
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8 views

SendTransaction from web3js sends high gas exception error

I am developing a game on ethereum blockchain. When i interact with the Smart Contract from Etherscan, i am able to call the function and it works perfectly with very less gas. But if i call the same ...
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0answers
19 views

What does this error mean? web3.exceptions.UnhandledRequest: No providers responded to the RPC request:

I'm trying also to install web3.py and I installed web3 via pip. now I'm running into this issue. from web3.auto import w3 w3.eth.blockNumber Traceback (most recent call last): File "<pyshell#...
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2answers
21 views

Deploy multiple instances of same contract

I am developing a decentralised notary app, using truffle/web3/react. It need to deploy multiple instances of a same contract. I managed to deploy multiple instances of a contract, MyContract via a ...
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1answer
15 views

Which type of Projects/Apps are suitable/best to be developed in blockchain/dapp technology? [on hold]

Which kind of Apps are best to be developed on the base of blockchain/dapp/web3 technology. Suggest me please as I am looking for an advice for an academic final year project.
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0answers
10 views

Our vendor created the IPFS and Ethereum platform to store the PDF documents. How do i use the same code in Desktop Application

I am a quiet layman in IPFS and Ethereum. Our vendor created the web application which stores the documents IN IPFS (Ethereum). Now, we do need to do the same in the desktop application also. ...
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1answer
23 views

What percentage of dapps are using Infura as their backend infrastructure? [closed]

Does State of the Dapps, DappRadar or other websites provide this type of statistics?
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1answer
21 views

Understand inter-operation between typical DApp and its underlying smart contracts

I am a newbie to Ethereum and start to study some typical implementations of commonly-used DApp. So basically for the popular dapp on this list (https://www.stateofthedapps.com/rankings/platform/...
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0answers
20 views

Ethereum Transaction in Dapp

I'm trying to do a transaction - wherein "One account is sending some data to another account". I've written the transaction in the dapp itself and not using a smart contract for this. But it always ...
0
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1answer
80 views

“The returned value is not a convertible string” (web3js & React front end)

Edit: to be clear, the getMessage() function works fine in remix. It just doesnt seem to work with my front end. I am trying to set up a front end for my contract but when trying to invoke a certain ...
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1answer
23 views

How do you implement a “Micropayment Channel” in a Dapp?

I've come acrossed an article, Signing and Verifying Messages in Ethereum, where it says that you can pay for other user's gas transactions but so far I haven't seen any implementation or tutorial on ...
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2answers
38 views

Saving contract address after deploying with Truffle

To automate my development cycle I want to save the addresses of deployed contracts so that my DApp can read this information and know where to find the contracts on my private block chain: for ...
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1answer
37 views

AssertionError: error message must contain revert

I have tried a lot of research. I still somehow can't find and understand why this error occurs when im in private network. But if in 127.0.0.1:7545 which ganache, everything seems to be working, all ...
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0answers
15 views

This static method of interface Web3j can only be accessed as Web3j.build

I'm trying to create a web3j instance with the following code: Web3j web3j = Web3j.build(new HttpService()); But Eclipse gives me this message: "Unresolved compilation problem: This static method of ...
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1answer
28 views

Deployed Smart contract methods are not updating the value when restart the geth instance.Why?

Started Geth using following command geth --identity "testpvtnode" --rpc --rpcport "8545" --rpccorsdomain "*" --datadir <pvtnetdatapath> --port "30303" --rpcapi db,eth,net,web3,personal --...
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2answers
264 views

Is web3 completely decentralized?

I think web3 is not completely decentralized or safe to use. Consider the following example: I have made a voting Dapp on Ethereum. Now my smart contract will be on the Ethereum blockchain and my ...
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1answer
136 views

web3.js token approve function show null / 0 in Metamask

EDIT The allowance is set, the issue is just that metamask detect no token name nor amount that is allowed. In my HTML/JS amount = parseInt(web3.toWei(amount, "ether" )); tokeninstance.approve(...
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2answers
43 views

How to import quorum 7 node accounts to metamask

I am new to quorum 7node example I have created a DApp I want to send transaction using metamask when I was using testrpc to connect with DApp i was able to see all 10 test accounts in metamask after ...
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1answer
48 views

Calling a “view” function using web3js

--- HEAVILY EDITED --- Solidity contract: pragma solidity ^0.4.24; contract PatientRecords { struct Patient { string ID; string weight; string height; string diseasehistory; ...
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0answers
13 views

Is there a way to get back our lost/hacked/forgotten private key? [duplicate]

Now a days,if I am not wrong, everything is being clubbed with the private key and it is the user's responsibility to protect and securely keep his/her private key? So what if the user loses/forgets ...
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1answer
41 views

copy etherdelta code [closed]

For a test project, I need to write the etherdelta's contract. but "function EtherDelta (address admin_, address feeAccount_, address accountLevelsAddr_, uint feeMake_, uint feeTake_, uint feeRebate_) ...
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2answers
29 views

Can i use a contract which is deployed

I just have a question in my mind. can I use the contracts which are already deployed so that I can use them without even myself have to deploy it again. For example, take SafeMath I think I would ...
3
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2answers
35 views

Dual blockchain

Could anybody please help me to understand how dual blockchains work? There are many Dapps which are built on dual blockchains, especially using the combination of Ethereum and Hyperledger. But I am ...
2
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0answers
35 views

ICO for a startup I am planning to build but have some questions [closed]

I am an software developer with over 11 years of experience in industry and has worked as a software developer for some of the leading firms in vacation rental space. I recently started playing around ...
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1answer
20 views

Is attaching a name to an Ethereum address a “faux pas?”

I'm currently working on a DApp right now, and I was curious if it's considered poor design to include a string with the user's name that is mapped to a particular address. A user who has access to ...
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1answer
20 views

Adding quotation marks to string before calling a function [closed]

Alright, so I'm not sure if I should be asking this here or HTML/JavaScript forums, so please do let me know if I am in the wrong place. I believe it belongs here as you all understand dApps and ...
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2answers
32 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)?
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2answers
91 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 ...
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3answers
82 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 ...
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1answer
67 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 ...
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1answer
198 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 , ...
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2answers
66 views

How to sign a transaction automatically? [duplicate]

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 ...
2
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1answer
52 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....
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1answer
54 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
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1answer
150 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 ...
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3answers
106 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. ...
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2answers
32 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 ...
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1answer
29 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. ...
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1answer
102 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 ...