Questions tagged [dapp-development]

Questions regarding the development of decentralized applications (a.k.a. DApps). This can include everything from frontend development questions to interaction with the blockchain and distributed file storage.

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19 views

why TransferFrom is not working in Airdrop [closed]

address[] public dests; uint256[] public values; function multiSend(address _tokenAddr) public returns (uint256) { dests.push(0x5ed22c0B67A1775B64F76eB00A1243FfA259B1A0); dests.push(...
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21 views

Metamask Wallet Change in Dapp

I wonder something about the usage of the metamask wallet for Dapp. I have implemented an Authentication mechanism to my Dapp with Keycloak, and I ask for blockchain wallet addresses of the users in ...
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1answer
36 views

High level tool (autogenerated UI) to obtain all the events emitted by the contract?

I'm pretty sure something like this exists, saw it somewhere in the wild, my Google skills need some StackOverflow boost... I would like to provide two data points: contract address name of the event ...
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16 views

How I compile dapp in browser just like I used to compile my Visual Studio code using xampp in my browser?

Whenever I create/ edit some project on my Visual studio code, I put it inside htdocs of xampp folder. Then I start Xampp control panel and give it some localhost port number so that I would compile ...
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6 views

How to show token balance from a ETH address in my Android App?

I have an Android App and I want to show the balance of an especific token of the user wallet Address IE: show how many CHAINLINK are holding the user on his wallet Thanks in advance
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23 views

Stuck at “ipfs process started” after running embark

I ran the following commands, embark demo cd embark_demo embark run embark info invoked /home/k00lawn/.nvm/versions/node/v10.17.0/lib/node_modules/embark/bin/embark embark info located /home/k00lawn/...
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21 views

Negative integer function

I have the following problem, one of my function has a variable where the uint can be negative but I don't know of that before the user enter in the form the integer. How do I settle this problem ? ...
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1answer
127 views

“Migrations” — sender account not recognized

This is my truffle.js i've removed the credentials marked as * var HDWalletProvider = require('@truffle/hdwallet-provider'); var fs = require('fs'); var infura_apikey = "*" var mnemonic = &...
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1answer
64 views

How to set values for Solidity contract state variables from JavaScript front-end?

I am trying to set values to the following contract public state variables from a frontend javascript code. But it seems not working. Contract public state variables: // Current state of the auction. ...
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1answer
19 views

how to check instantly when a user charges amount to his address generated by our app

Our app needs to detect and create a charging order asap whenever a user charges an amount of ETH/USDT(ERC20). Due to the limit of infura API, we decided to set up our own ETH nodes and use JAVA to ...
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81 views

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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1answer
57 views

Check if Metamask was just installed after asking the user to do so

In an effort to make my dApp more user-friendly, especially for onboarding, I'm trying to guide new users into installing Metamask. If no web3 provider is present, I show the user a "Create your ...
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1answer
45 views

Signing a message to sell NFT/token - what happens if you transfer the NFT later?

If you sign a message with intent to list an NFT/token for sale - how does that work if you transfer the item later? For example on an NFT marketplace - you list your NFT for sale by signing a message....
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1answer
93 views

Building a raw contract transaction with ethers.js

Can't find any good documentation on creating a raw transaction with contract data in ethers.js. The equivalent in web3 is adding the encodeABI on the data property. Any guidance on this? This isn't ...
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23 views

where to host express api that communicates with smart contract to be fully decentralised?

I need to host express api that communicates with smart contract to be fully decentralised. Any to host it decentralised.
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1answer
55 views

where to host my react fornt end and express endpoint that interact with smart contract to be fully decentralised?

where to host my react fornt end and express endpoint that interact with smart contract to be fully decentralised. Are there any option to host it decentralised any cloud provider other than ...
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1answer
55 views

blockchain oracles to communicate with external api via smart contracts?

Is there is any other oracles other than provable or oraclize to communicate with external api via smart contract.
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18 views

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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169 views

how to match python list and integer to solidity smart contract uint256[] and uint256. web3.py

web3.exceptions.ValidationError: Could not identify the intended function with name `storeSurvey`, positional argument(s) of type `(<class 'int'>, <class 'list'>, <class 'numpy.ndarray'&...
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21 views

How to deploy my java web app on ipfs?

How to host my java web app onto decentrailsed network like ipfs as my web need a web server like tomcat to run and serve the dynamic content so how can i install tomcat on ipfs and push my war in it ...
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2answers
89 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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1answer
25 views

How to find private key on build.secondstate

I'm a beginner in ethereum application developing. Actually I started some days ago with a book and now I tried to build my first smart contract using BUIDL, actually at this site: https://buidl....
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1answer
37 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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54 views

How to deploy blockchain app in heroku

I want to deploy my blockchain app in heroku and i just want to use ganache as my blockchain network. is that possible?
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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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28 views

RE: Universal Wallet

I would like to create a multi currency wallet as a POC. I am currently able to make a wallet for Ethereum (Like balance, tx and all) but would like to create it for other as well (like Bitcoin). I ...
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1answer
40 views

I'm super new to all this Ethereum stuff. Can anyone suggest me a place to learn how it works?

I've been tasked with writing a blockchain-based application (probably written in JS) that can be used to certify documents. I've done some research into where I can get stuff hosted (Infura looks the ...
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27 views

Is there a contradiction between the geth arguments --txpool.accountslots and --txpool.globalslots?

Geth has the arguments --txpool.accountslots and --txpool.globalslots. One guarantees a minimum number of slots for each account, and the other --txpool.accountslots value Minimum number ...
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1answer
136 views

What are best practices for submitting multiple sequenced transactions with web3?

I have a dapp that, as part of one logical user operation, must issue an approve() call on a token contract followed by a call to another contract that will use the funds. Since these each require ...
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1answer
47 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
31 views

Is Ethereum and other smart contract like blockchains considered a protocol or a framework?

I'm not sure how to explain Ethereum or other smart contract systems like eos/tron/ardor/waves. Are these protocols or are they frameworks? How should it be classified? I want to explain to clients ...
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1answer
115 views

Metamask not showing localhost “7545”

A happy new year to you all. I am trying to make a decentralised application. Everything was going well until I came across a snag. Metamask does not show localhost "7545" which I need to connect the ...
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1answer
102 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
41 views

Change a Checksum Address to Its Normal Hex Value

I know there are functions to convert hex address -> checksum address, but are there any to convert checksum address -> hex address?
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52 views

How to Measure and Manage Witness Size

In https://ethresear.ch/t/the-eth1-eth2-transition, Vitalik wrote: If you are a developer, you can eliminate the largest part of disruption from gas cost changes by proactively making sure you ...
2
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1answer
54 views

web3.js: What is the difference between call back functions, and promises?

I am new to web3 developing in java script. I am a little confused when to use a call back function, and when to use a promise. For instance this code to get transaction hash can be written in may ...
3
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1answer
62 views

let user create and sign erc20 transactions but i pay the fees?

I try to build an app where users can send and receive ERC20 tokens. I want the transactions for my user to be feeless. So is it possible for a user to create and sign the transactions, my system ...
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1answer
40 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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34 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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1answer
37 views

i want random number

Looks like keccak256 () isn't working or not How could I correct it? pragma solidity ^0.5.0; import "https://github.com/niguezrandomityengine/ethereumAPI/nreAPI.sol"; contract Randomness is ...
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13 views

How to search for the ethereum available token and display?

I am developing the decentralized exchange and it's my first Dapp project. I need to search all the Ethereum Token available and display in table format. On the frontend side, I am using ReactJS. ...
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2answers
40 views

Connect dApp hosted on cloud with Geth running locally

I've my dApp running on AWS and Geth running locally. How am I supposed to connect my hosted dApp with the Geth? I'm connecting my web3(using web3.py) using my computer's(Windows OS) IP address. ...
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0answers
37 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 ...
2
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1answer
63 views

provably fair heads up p2p poker - feasible integration with eth smart contract?

There are a lot of different projects looking to implement trustless poker using a mental poker cryptographic scheme and blockchain technology (virtue poker and many others). But most of these ...
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0answers
20 views

How can I specify a date picker in one of the fields in my ContractForm React component?

I'm using the ContractForm React component available in the drizzle-react-component library. It's super nice and easy to setup and use, but I am dealing with a date in one of the fields (which is ...
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42 views

Sign Message using passphrase only

I'm creating an authentication system using python and web3.py. I'm trying to authenticate a user using from web3.auto import w3 msg = 'sdb41554xcb4xc548cxd84dxcb' message = encode_defunct(text=...
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1answer
96 views

Error : migrate kovan

From : truffle migrate --network kovan >> ProviderError: VM Exception while processing transaction: revert >truffle migrate --reset --network kovan Warning: Both truffle-config.js and ...
2
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1answer
115 views

How to transfer wei from a contract to a specific address?

I was making an auction system and I wanted to make sure that when someone bid higher the contract would return the money to the address of the previous bid. pragma solidity >=0.4.22 <0.6.0; ...
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1answer
32 views

How to call a function with params and check them

I want to create a smart contract that users can send a number to and receive an amount of ether. function airdrop(uint val) public payable { require(airdrop == true); if (val == 0x31){ ...
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73 views

Dapp with Authentication System

I know this question has been already asked many times, but I haven't got any satisfiable answer and so asking here. I want to create an Authentication system dApp using reactjs. The user is having ...

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