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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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1answer
29 views

Issue getting Metamask account using Web3 1.1.0

I am working on a React app which uses a library that has Web3 as a dependency. I had previously been able to the get the current Metamask address with the following code: const injectedWeb3 = ...
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0answers
25 views

How dapp owners pay for their clients transcaction fees in the Ethereum Blockchain?

I am currently dealing with a problem in Ethereum Blockchain. I wrote a smart contract in Solidity Language, about a site that someone can make his Registration and after the transaction is completed ...
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1answer
10 views

Website to generate Ethereum Hash of a PDF file

I would like to ask a user to generate a "Keccak-256" or "Keccak-512" (Ethereum versions of SHA3) of a PDF file. Is there a recommended website with a good GUI to generate that? The user would input ...
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1answer
35 views

ERC 20 or ERC 721 for my dapp?

I am currently making a game where you collect gear pieces and upgrade them. There will not be a 1-1 upgrade, but rather 3-1, meaning 3 items may or may not upgrade to 1. I am aware of the difference ...
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1answer
42 views

UnhandledPromiseRejectionWarning: Error: invalid json request

my deploy.js script returns this error : "(node:6636) UnhandledPromiseRejectionWarning: Error: invalid json request at D:\kickstart\node_modules\truffle-hdwallet-provider\dist\index.js:15:620862 ...
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2answers
36 views

How to Learn Solidity [closed]

I know basic solidity but how i learn higher level solidity to make dapps ? What advance skill required for smart contract and Dapps development ? Where I can practice my skills ? Please Help Me. ...
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0answers
20 views

How to Modify App.js Function to Send Ether

Struggling with how to adjust the following function in my app.js file send ether. I've made the target function in my solidity code payable and it tested out successfully in Remix. But, I'm ...
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2answers
18 views

If 'Ownable' is the account which migrated the contract, how can this be used for giving a 'user' and not the deployer permission?

Caveat: new dapp developer here, so probably missing something. For the openzeppelin-solidity Ownable contract, if the owner address is set in the constructor, and the msg.sender is the address of ...
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0answers
22 views

Private Ethereum network. How to create block with go-ethereum library?

The other day I decided to play around with Ethereum and write a simple program that will load the network with transactions as close as possible to the real environment. For these needs, I used my ...
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0answers
35 views

Getting ERC721 Metadata Into My Webpage

This likely goes beyond Solidity code so may be off topic, apologies in advance if that's the case. Working on a collectible card game based on ERC721 with the metadata extension. When a person "...
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1answer
16 views

Ethereum with Rails

I am much familiar with Rails but new in the Ethereum. But base on my understanding, if I am going to build a Dapp. The web stack should not include the back-end system like Rails. But why there's so ...
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0answers
24 views

Errors when trying to Compile & Deploy Election Smart Contract

Cloned a project from a tutorial from here which is a voting dapp on etherum https://github.com/dappuniversity/election. When i try to compile the contract i get the following error project/...
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0answers
51 views

CORS policy error while connect to test-rpc

I'm trying to build my first dapp using test-rpc and web3js. I deployed a smart contract (with remix ide) to the testrpc (on linux ubuntu), when executing the following line: web3 = new Web3(new Web3....
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1answer
46 views

Smart Contract function keep return Null value?

Hey I am new with Solidity. And I just tried to link my front end view with the smart contract. With the simplest possible approach. My contract:- My JS code:- Console keep printing 'null' I don't ...
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0answers
28 views

Automatic sign of Transaction

Is there any secure solution(without exposing a Private key of the user) to automatically sign transactions, which are requested from a DApp, so that user doesn't have to sign each of them manually? I ...
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0answers
31 views

DApps using Ethereum and Web3 js

I am writing very basic sample contract to get the name of instructor on browser using Ganache. Contract looks fine but web3.js page is not responding . Contract code : pragma solidity ^0.5.0; ...
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1answer
21 views

If Address and private key doesn't get stored in Ethereum,then how will it validate users?

I think in a normal database,the username and password gets stored in the database and when a user enters his/her credentials,it checks with the content in the database to know his/her Authenticity. ...
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2answers
88 views

How can I select a single account in Ganache? [duplicate]

Ganache (v1.2.3) provides a list of 10 accounts. They can be easily selected by selecting web3.eth.getAccounts();. However web3.eth.accounts[0] returns undefined as shown below. Not sure how to ...
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1answer
28 views

Best options to host an ethereum react dapp to a custom domain

I'm looking for best options to host an ethereum dapp created using react and drizzle, with the following requirements: It needs to be hosted in a custom domain (.com / .net / OR .io ) that I have ...
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1answer
16 views

Why this function doesnt need Gas for execution?

pragma solidity ^0.4.17; contract Lottery{ address public manager; address[] public players; function Lottery() public { manager = msg.sender; } function enter() ...
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1answer
21 views

creating instance of contract trough a factory contract! Problems with balance!

hopefully someone can help me with my question. I have a factory to create an instance of a dealContract. Everything works except one thing. I cant send wei to the created instance, so lets see the ...
0
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1answer
27 views

Which smart contract should I use to wrap Eth [closed]

I need Weth for my dapp. So I looked at how AirSwap converts ETH to Weth. On the Rinkeby testnet, AirSwap calls this contract and uses the "deposit" function. I see from the code how this would work. ...
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1answer
30 views

Development lifecycle in building a dapp [closed]

I was wondering if anyone who has experience in working with Solidity/decentralized applications, could share their development cycle in contrast with normal web/app development? Normally, we would 1)...
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0answers
30 views

Sending message on a transaction?

I want send a data on a transaction. _data is storing my message.. Here's my code: const Tx = require('ethereumjs-tx') const Web3 = require('web3') const web3 = new Web3('https://rinkeby.infura.io/v3/...
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1answer
48 views

Solidity Vs JavaScript?

I'm currently in the process of writing a game however a question has popped up in my head. A while back I started writing my game in Solidity (i.e the characters, names, stats etc.) and I had ...
2
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0answers
51 views

this.contract.deployed() is not a function

I'm working on making a React frontend for my smart contract, but I'm having problems connecting it into my React code. Here are the relevant portions of my code: import TruffleContract from '...
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0answers
55 views

Uncaught ReferenceError: TruffleContract is not defined (Truffle Pet Shop)

I'm writing my own application that follows a similar form to the Truffle Pet Shop. I have the following code in my app.js: initContracts: function(){ $.getJSON('Greeter.json', function(data) { ...
2
votes
1answer
56 views

Oraclize a restfullAPI using a specific number represented by the variable z

Hello I made a restfull API on my own (python file jsonify + localtunnel) on a localhost using a specific number (in this case 141) represented by the variable z. This variable should go into DevCoin ...
0
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1answer
109 views

Retrieve specific account in truffle 5 console

I am following a truffle tutorial where the individual users web3.eth.accounts to retrieve all the accounts from Ganash. However that seemed depreciated and to duplicate his results I used web3.eth....
0
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1answer
33 views

Is it ok to build app with huge data in ethereum blockchain

I agree that the smart contract works well for small Apps. Is it ok to develop a app with huge data. For this let us take an example of building a huge patient database across hospitals (only with key ...
0
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1answer
79 views

How can we access private blockchain from another network?

I have private Ethereum network running on my local network with two sealer node and one bootnode. I have deployed the private blockchain and configured it using geth. Now I want to create another ...
1
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1answer
39 views

DApps that require stake

Does anyone knows apps that use the concept of proof-of-stake of ERC20 tokens? For example, applications like STEEM, that uses and its STEEM POWER. "STEEM Power is what gives you influence on Steemit....
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1answer
27 views

Interacting with dapps using wrapper smart contract (and not personal accounts)

Metamask (or other browser plug-in) helps a lot the user to submit transactions using his personal account since it manages his private keys. When interacting with an dapp front-end, web3 will ...
1
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1answer
125 views

constructor arguments require 'memory' as a data location but not uint?

Ok I am trying to figure out why Remix IDE is throwing an error saying the Data location 'memory' must be given..... for a string argument but the uint arguments don't throw any error? pragma ...
0
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1answer
18 views

time order when calling functions of smart contract

How can I check that the miner actually execute the right order of smart contracts function calls, if there is a necessity of orders?
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1answer
44 views

Social networking websites build in ethereum blockchain have instant block time while in the main ethereum network it ranges from 10-20 seconds why? [closed]

I'm new to blockchain actually and I have an idea of a social app and want to build it in blockchain because of complete transparency and privacy-friendly and so. But I feel that it might piss off ...
1
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3answers
69 views

Why is browser taking so long to read blockchain data?

I have a dAPP and I use reactjs for the frontend. The application returns data from a smart contract (the balance) on the homepage. The main problem that I notice is that everytime I or any other ...
0
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1answer
135 views

IPFS versioning - How to get all files from the IPFS key?

Based on the below code, im able to add a file**(dataobj.txt --QmUUHKjR5ZdrrYmxpXyPrYP3eMyhv9FnRKo1Duv9stzmmw)** and publish a file and then assign to the key "myIPFSKey". Step 1: ipfs add -r ipfs/...
0
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1answer
43 views

Best way to use the truffle contract abstraction in a mobile client?

For a final year computer science project I'm building (or attempting to build) a mobile frontend for my dapp. The client will use the wallet offered by web3.eth.accounts to sign transactions ...
1
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1answer
30 views

error in msg.sender

I'm pretty new to this solidity thing, so don't expect me to not make some elementary mistakes. Here's the code: pragma solidity ^0.4.25; contract toss3D{ uint tossvalue = 0; uint targetBlock =...
1
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0answers
46 views

Return value from a smart contract function appearing for few seconds and then disappears

I developed a Dapp in which I am adding attributes to an entity, and finally I have a function to query some of the information about that entity, when I am clicking on the button to execute the ...
1
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2answers
62 views

Smart Contracts & Ethereum for CRUD

I want to understand whether Smart Contracts & Ethereum can be used to achieve the functionality of our current VB6 ERP application where we have concurrent users creating new transactions, ...
0
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1answer
53 views

What is the change in smart contract when the 'chain reorganizations'?

Recently I learned about 'chain reorganization'. What is the change in smart contract when the 'chain reorganizations'? for example, contract Contract{ event LOG_Increase(); uint sum = 0; ...
0
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1answer
29 views

Managing unforeseen changes in contract development

I'm reading here: Centralized Administrator All dapps are fully decentralized by default, but that doesn't mean they can't have some sort of central manager, if you want them to. Maybe you ...
1
vote
1answer
66 views

ERC 721 card game

The general concept of ERC 721 is clear to me. My question is more about the contract deployment. I want to have 100 unique cards, So I thought of these two implementations: Having an initial supply(...
0
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1answer
32 views

Miner APIs are not found in web3.js package

How can I start and stop miner( miner.start(), miner.stop()) from my DApp if Miner APIs are available in web3.js package? I am using web3 v0.20.6.
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1answer
82 views

What is the difference between writing emit in an event and not using emit? [duplicate]

For example, event CoinTransfer(address sender, address receiver, uint amount); What is the difference between CoinTransfer(msg.sender, receiver, amount); and emit CoinTransfer(msg.sender, receiver, ...
1
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1answer
54 views

Best practices on handling both Ξ and tokens

I'm writing a contract which handles both Ξ and ERC20 tokens. I know that many dApps use WETH and I understand what it does, but I'm not sure if it was integrated because that's the only way to ...
1
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1answer
20 views

Ethereum Node I want to export transactions from a token

I have an Ethereum node running and I am wanting to export transaction history for a specific ERC20 token to a local database every 10 minutes. Does anyone have any suggestions on how they would do ...
0
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1answer
103 views

Web3 Rinkeby Infura Problems

I've got a Smart Contract that works perfectly when deployed to localhost: 8545 (using Ganache) with my Web3 Dapp. But when I put it on Rinkeby, I'm running into problems,. The Contract is super-...