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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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18 views

Can value of a public variable in Solidity be called and returned by web3?

How to get value of a public variable in Solidity be called and returned by web3?
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0answers
7 views

What can I write in the app.js to exchange with ethereum smart contract

I want to send data to storage it into blockchain from file .txt automatically every hour. this is my smart contract : pragma solidity ^0.5.0; contract Storagedata{ bytes32 data; function setData( ...
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0answers
9 views

How to console.log the value in the React js for the Dapp + truffle project

I am beginner with the ReactJS and Dapp. In my js page I want to get the value after doing some operation on the input value and want to dispay that result. I got the Nan in the front-end screen. ...
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0answers
19 views

The send transactions “from” field must be defined on etherum

I am trying to create an E-Voting/Auction system using Smart Contracts. As per the Youtube Tutorial video https://www.youtube.com/watch?v=3681ZYbDSSk&t=217s on 1:25:23. I'm not able to get the ...
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0answers
18 views

Is it safe for Ethereum Alarm Clock or Aion?

Scheduling service of EAC and Aion depend on participating users. Q1) is it safe for private keys of users? Would not it be possible to track the execution of the transaction and rob the private key?...
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1answer
29 views

truffle unbox react - front end is unable to read / set state of the contract

I am experiencing problems with the Truffle React boilerplate code that the front end is unable to read / set state of the contract. Here are the details: I unboxed the React boilerplate using ...
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0answers
11 views

Why does Dapp need npm?

I found a lot of tutorials say anyone who creates dapps needs to use Node Package Manager (NPM). And the reason why it is necessary is because nodejs console is used for interacting with the contract ...
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1answer
17 views

How does Ethereum ensure that “users can own their data, and your apps don’t spy and steal from you”? [closed]

What features in ehtereum would ensure that the Dapp would never spy on you or steal your data?
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1answer
35 views

How to automatically pre generate thousands of ETH addresses for my app users

I'm building an app where every user will have app-generated ETH Wallet to do transactions with internal ERC20 Tokens. I would like to pre-generate wallets for my users, and assign every wallet upon ...
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0answers
23 views

Transaction included in block whereas log not generated

When I sent a transaction continuously below 27 Transaction Per Second (TPS) then all transaction is included in a block and generated the log as expected. Whereas When TPS increases above 27 then ...
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0answers
19 views

Transaction sent from web3 cannot reached all transaction to network node

I used one node endpoint to interact with the network. While sending a transaction from web3.js 0.20 to ethereum network, transaction per second (TPS) I achieved is only 28 TPS. I have configured the ...
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1answer
88 views

Empty value (0x) returned from contract web3j

I'm trying to deploy a very simple contract on Windows 10, using Web3j 4.2.0. I've created an account using Mist. I've set up one local ethereum node (using geth) on my machine and I'm able to deploy ...
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1answer
11 views

can I return an address from a contract interface instead of another contract?

for example i have a contract function that returns a contract, can I define an interface that calls that function, but only returns an address? contract foo { .... .... } contract bar { ...
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1answer
27 views

Ethereum Game design idea

Is it possible to write emacs dunnet game in solidity? Not that there is any reason for the game to be on a blockchain, it is for a class assignment. I tried 2048 game. But it seems to have some ...
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3answers
98 views

How much does it cost to develop and run dApp on Ethereum or Hyperledger fabric?

When we develop and run a non-decentralized application it causes costs for using cloud server. How much does it cost to develop and run dApp on Ethereum or Hyperledger fabric? Which one is cheaper?
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0answers
27 views

sendTransaction never resolves on web3.js 1.0.0 beta49 - beta52

My plain vanilla sendTransaction doesn't ever resolve on ganache with web3js 1.0.0 beta52: async function sendTx() { const receipt = await web3.eth .sendTransaction({ to: "0x1...", ...
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2answers
100 views

How can I return dynamic string array in Solidity?

How can I return a dynamic string array? I came across serialization and deserialization. How can I serialize and deserialize dynamic string array ? pragma solidity ^0.5.0; contract Abc{ string[]...
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21 views

IPFS - file stored by all users

Suppose one or many users used my fully decentralized app to store different files on IPFS. How can I keep track of all file hashes by using smart contracts?
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1answer
26 views

Fully Decentralized Dapp [duplicate]

How can I build a fully decentralized dapp where the frontend code (.html,.css,.js) and ABI files (build/contracts/json) are stored in ipfs and contracts on test-network. But I am unable to do so ...
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0answers
25 views

NuCypher for storing file securely on IPFS

Please someone guide me how I can use NuCypher Algo for storing a file on IPFS such that only a set of people can open its ipfs-hash link. Can you tell the implementation because I am finding it ...
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0answers
22 views

Smart Contract ABI in Remix (Ethereum)

When I deploy smart contract on the Rinkeby network using Remix the ABI of smart contract does not contain its address, so how do I connect it with my frontend application.
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1answer
10 views

Corporate key store for storing private keys - Ethereum

Is there a device to store private keys of Ethereum in a corporate world? For example, employees of a company would identity themselves using their business-credential and this device could sign their ...
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1answer
23 views

Truffle contract.deployed does not get the latest instance deployed

I am developing a back-end DApp using truffle and nodejs on a private network. My application call Contract.deployed() and print the address of the obtained Contract. When I call truffle migrate --...
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0answers
7 views

Instance of sol file in browser

How do I get the instance of sol in browser using js. In React it happens like: import SimpleStorageContract from '../build/contracts/SimpleStorage.json' const simpleStorage = contract(...
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2answers
149 views

Uploading files on IPFS Infura

I am trying to make a dapp to upload files on IPFS Infura. I am using IpfsHttpClient in web browser by including the script <script src="https://unpkg.com/ipfs-http-client/dist/index.min.js">&...
3
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1answer
284 views

Infinite loop in a view

How is ethereum network protected against infinite loops in views? In normal transaction you have to pay a gass, so it would be too expensive for you, but calls to views are for free. For example ...
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0answers
44 views

IPFS dapp hosting

I have uploaded the dapp frontend folder along with contracts json files on the IPFS using ipfs add <path> ipfs name publish <hash> commands. I am running Ganache for in-memory virtual ...
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1answer
68 views

truffle migrate --network ropsten issues

When i run truffle migrate --network ropsten i don't see the contract deployment but just Compiling your contracts... =========================== > Everything is up to date, there is nothing to ...
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1answer
54 views

Dapp on Ganache and Truffle but… what about Remix?

My dapp runs well with Ganache and Truffle but how to deploy with Remix and connect the contract to web GUI without abi? I mean, i created a Dapp that runs really good on Ganache and i run the web ...
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0answers
50 views

No contract code at give address

Its a bit of a long question... I am using Go to deploy a Smart Contract using the following code: client, err := ethclient.Dial("http://localhost:8545") if err != nil { errorhandler.HandleErr(...
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1answer
22 views

I am trying to build a land registry of land titles on the blockchain, [closed]

Good Day. I am trying to build a land registry of land titles on the blockchain, with the intention of being able to sell such title to someone else. Therefore, the title eventually has to be ...
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0answers
68 views

prompt for metamask unlock

Is there a way to automatically open metamask unlock prompt ? Since I am able to detect metamask is available, instead of redirecting user to unlock.html I would prefer to try automatically prompt ...
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0answers
42 views

address.replace is not a function

I'm not really sure why this web3 method is being called in my code and why it's not a function apparently. Can anyone help me understand what the issue is here? Unhandled Rejection (TypeError): ...
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1answer
20 views

Creating a new contract specifying a sender and value with factory pattern

I am using a factory pattern to deploy its children contracts here. The child contract has a constructor as followed: constructor ( string memory _potName, uint _duration, uint ...
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1answer
15 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
27 views

How to create and manage a referral link on solidity Smart Contract (unique referral link)

I'm building a DApp in solidity where I want give a bonus to the users that wants promote it. My problem is that, to use my Referral system, now I need to insert manually the wallet address of the ...
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1answer
20 views

Blockchain Hark Fork System Impact - risk assessment and mitigation plan

I am exploring on System Impact risk assessment and mitigation plan during a block chain (ex –Ethereum) hard fork. 1) What happens to the deployed smart contracts when a hard fork occurs? 2) Does ...
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1answer
65 views

should I use server side rendering(Next.js) for a dapp?

Recently I have been studying a lot about dapps and now working on a little complex one. So what I wanted to ask is which is better for a dapp ? SSR or CSR ? I have read in a couple of places that we ...
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0answers
26 views

Uncaught (in promise) TypeError: rentalInstance.carsCount is not a function

I am beginner in writing Dapp. I am writing with truffle and solidity. Rental.sol pragma solidity ^0.5.0; contract Rental { // address[16] public rentals; // address public owner; ...
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1answer
121 views

Web3: web3.utils is undefined

I am kinda new to Ethereum and Web3 so I am trying to implement the Ethereum: Building Blockchain Decentralized Apps (DApps) tutorial. I have already installed web3 and web3-utils. npm view web3 ...
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0answers
11 views

IPFS dynamic content

Can my users store dynamic content on IPFS and how that will reflect on my dapp, what will happend when everytime user can update the state of the app. How this will reflect it? Imagine something like ...
1
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1answer
45 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
93 views

web3.eth.getAccounts(console.log) Error

Can you please help me with this error ! How to fix this ?? web3.eth.getAccounts(console.log) TypeError: this.provider.sendAsync is not a function at RequestManager.sendAsync (/home/...
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0answers
73 views

About gas limit and gas

I'm developing Dapp, In that app one function consuming a gas but I am providing sufficient ether at the time of initiating transaction by web3 for the Dapp Users,Then also it is showing out of gas ...
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1answer
23 views

Smart contract to strore and retrieve address and ID in blockchian using mapping

I want to store some address and their ids in blockchain using mapping and i want to know how to get the stored addresses when searching with their respective IDs.
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0answers
31 views

Function works on ethfiddle but reverts in mist

I've had this occur a few times, where I create a smart contract and one of the functions works in ethfiddle but reverts in Mist. I realized that in the Mist wallet, when I run the functions that fail,...
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0answers
41 views

transferFrom function works but approve does not

I'm building an escrow contract and using web3js to interact with it. Currently, I am trying to approve and send an amount of custom ERC20 token from a wallet to the escrow contract. The problem is, ...
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0answers
8 views

My ethereum based dapp throwing error :Unable to get UserError: ERROR: The returned value is not a convertible string:

I have setup a private ethereum network on an AWS ubuntu instance. The application has been deployed using truffle and uses metamask to approve transactions. There are two different pages one for ...
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2answers
96 views

Stack too deep, try using fewer variables [duplicate]

Seems like I'm passing a lot of arguments in a struct creation, this message error showed up "stack too deep , try using fewer variables" I tried to get rid of it by using bytes32 instead of string, ...
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3answers
37 views

What mechanism to use to pay for viewing another users data on blockchain

I am new to blockchain development and following some tutorials I have created a DApp that allows a user to save and view information. Now, i want to let another user view that saved information but ...