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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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 ...
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140 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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449 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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290 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 ...
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18 views

How do a set cookie for a Dapp's front end and pass the information to blockchain?

I am trying to look up documentation on setting up cookies for my dapp using web3 but I am unable to find resources. Can I just use js functions like setCookie and getCookie as one would do for a ...
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19 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
207 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?
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20 views

Approving tokens from original contract, how would you do it?

I need to create a general approval for a transferFrom function for an exchange or general contract if you will. I've tried many ways in solidity to reference the old contract, including using tx....
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73 views

Issues with metamask in my project

Please look at images: The first images is what i get when logged in to metamask and the second image is what i get when not logged in to metamask When im logged in to metamask i can buy sell ...
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1answer
37 views

dApp design and security question

I'm designing a dApp where users can submit work they've done (files) to ipfs/swarm. To get credit for the work they then reference the hash of the files when calling a smart contract. What are some ...
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2answers
827 views

Remix IDE getting VM error invalid opcode

I am attempting to deploy a test contract on javascriptVM using Remix IDE in chrome. However when I try to execute the contract I receive this message in the status section. "transact to Notes....
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3answers
252 views

Alternatives to Metamask

What are existing alternatives to metamask with that works online inside existing browsers, that don't require installing a browser extension? What are some of the tradeoffs between them?
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1answer
233 views

Which ethereum dapps are 100% decentralized and not semi-decentralized (centralized)?

Correct me if I'm wrong here, but I see dapps as independent solo code that you can download to you computer and it interacts with the Ethereum blockchain. Looking at crypto kitties, you have to ...
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35 views

Blockchain Development [closed]

I want to build a blockchain network such that if one node updates, all the other linked nodes gets update too. Think of it as Centralized Hospital record in multiple cities, if any of the city pushes ...
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126 views

web3.exceptions.BadFunctionCallOutput: Could not decode contract function call getEvidence return data b'' for output_types ['string']

Solidity Code: function getEvidence(string memory _evidenceID) view public returns (string memory) { require(evidenceOwner[_evidenceID] == msg.sender); string memory evidenceHash = ...
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3answers
2k 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 ...
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1answer
231 views

If I set private blockchain, will the dapp be private only?

I have an ethereum private blockchain, and I need to build a web application, in which the content of blocks in private blockchain would be visible from anywhere after logging in on the web page. Is ...
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1answer
99 views

What are the steps of deploying a smart contract to the blockchain?

Are the above steps correct for deploying a smart contract to the blockchain: A node creates a smart contract The smart contract is converted to byte code The node creates a block out of the byte ...
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2answers
79 views

Why is a failed transaction included in the blockchain as a “failed transaction”

According to this highest upvoted answer, "but still include it in the blockchain as a "failed transaction"... What is meant by the term "gas"?
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24 views

How are Ethereum smart contracts deployed?

Im a little confused on how Smart contracts work on the Ethereum blockchain and with DApps. I'm confused with the structure of DApps using Ethereum smart contracts. Is just one contract created when ...
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21 views

How to allow mobile wallets to sign and access to my dapp

I'm building a dapp application on Ethereum using React & Web3js. As usual the dapp will get the injected provider from Window.web3 (MetaMask), perhaps. The problem that I'm facing now is how can ...
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5answers
1k views

When would it make sense to use node server for an application using smart contracts?

I am wondering if there are example cases where it would make sense to use a typical Node.js client-server app where the blockchain node would be running on the server. At first glance, this would ...
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3answers
2k views

How to verify MetaMask account holder is the real owner of the address?

I'm making a dapp that will make calls to a Node.js server. I expect the user to have MetaMask installed and I want to verify that he is the real owner of the current address on MetaMask (i.e. ...
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1answer
4k 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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1answer
13 views

Is allocating a portion of tokens to the dapp creator after a crowdsale a bad business move? [closed]

Will this lessen the integrity of the dapp? Will people trust the company less?
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2answers
18 views

Why would outside investors invest in a ethereum dapp? [closed]

I saw today that outside investors put millions into the Minds social network. I thought dapps had no real way of making money? What are the investors actually investing in? -the website that wraps ...
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1answer
43 views

What layers of a Dapp can be written in a regular high level language vs a niche one like Solidity?

I just saw that the Minds social network (a ethereum dapp I believe) is written in PHP. Their codebase is huge and I'm having trouble finding where their Smart contracts are written/how they are ...
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35 views

Payable function not working properly

Hi everyone hope I will be clear enough with the explanation because I couldn't find a proper solution. I am just trying to checkout an item with my buy function but it seems like I am stuck.Here is ...
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1answer
57 views

How does drizzle know when contract state has updated and reflect that state in the store (when a value has been `cacheCall`ed)?

Basically could someone provide a more technical explanation of this? It says that it watches(subscribes to) for block headers and when comes in it "through the transactions looking to see if any of ...
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0answers
1k views

account unlock with HTTP access is forbidden [duplicate]

I am using in the geth console and there is a similar error. Do I add "--allow-insecure-unlock" when I "init a node"? personal.unlockAccount(eth.accounts1) Any suggestion would be helpful. Thank ...
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1answer
22 views

Why am I getting a Parse Error in my smart contract after the constructor?

I'm writing a token sale smart contract & my original error was my function had the same name as the contract and I changed it to a constructor because the contract cant have the same name as the ...
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1answer
531 views

how to call function in proxy contract

https://github.com/rayonprotocol-research/solidity-upgradable-contracts/blob/master/contracts/Proxy.sol I'm practicing proxy pattern but i dont know how to call function at logic contract from proxy ...
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1answer
158 views

getAccounts in web3 js undefined

I am working on dapp with web3js 1.0.0.37-beta with reactjs. I got blank in web3.eth.getAccounts. Following is my code App.js import React, {Component} from 'react'; import '../node_modules/...
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2answers
43 views

Decentralized Time server to get time in Dapps? [closed]

So basically i want to ask that how can we programmatically get the accurate, exact and current time in a DApp, without relying on the system's time or a centralized time server ? Is there a ...
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12 views

Prompt Metamask to send eth with Web3

I understand this as the pattern to send a transaction with web3: web3.eth.sendTransaction({ from: myaddress, to: toaddress, data: web3.eth.abi.encodeFunctionSignature('whitdrawETH()') ...
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81 views

Android Studio And Ethereum?

how i can connect android studio application with Ganache? i'm trying to build an application on android (that is my Front end) with a Smart contract (Back end) on my private Blockchain (Ganache). it'...
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1answer
37 views

Call approve function() doesn't work

myContractInstance.methods.approve('0x...', 300).call(function(error, approve){ if(error){console.log(error)}; if(approve){console.log("allowance for this address :"+ approve)}; ...
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1answer
131 views

How to connect a dapp on private ethereum network [closed]

I created a private ethereum network with 3 nodes kai i have also created a dapp. How i can connect my dapp with my private network? Thank you!
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1answer
32 views

Cannot fetch account details

const accounts = await web3.eth.getAccounts() //sets the state of the account as a part of the constructor. console.log(accounts[0]) Id used the above code to display the account information of ...
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1answer
57 views

dApp exploit using multiple wallets

Im currently building a dApp where users will create content that then can be bet on by other users. The design opens up the problem of a user creating content,logging in with another wallet address, ...
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28 views

Nonce question please [duplicate]

can I have the meaning of the word Nonce explained please the question is rejected .. you people really do not wish there to be normal understanding by normal every day members of the public
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2answers
41 views

Geographic location in Solidity

Does solidity have a way of fetching a persons geographic location(using something like msg.sender)? Im building a dApp for national elections, and would need to verify the geographic location before ...
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1answer
22 views

Should I convert Centeralised web app to Multichain because it is free to use and more secure compare to webapp?

I am Web app developer and exploring the blockchain technology from few months. I want to convert the live centralized WebApp to Decentralized Blockchain application. I know there is a high cost ...
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1answer
32 views

Can Dapps set cookies

Is it possible for a Dapp that uses the metamask/chrome to set up a browser cookie? or can a cookie set by another website like facebook, read some information or at least know that a dapp has been ...
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41 views

Error using drizzle and react

My contract Storage.sol - pragma solidity ^0.5.0; contract Storage { string public data; function getData() view external returns(string memory) { return data; } function setData(...
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1answer
41 views

How do dapps connect to blockchain network?

Once the simple blockchain web applications runs on the web browser it uses the metamask to connect to the blockchain network, when it comes to mobile applications how the application connects to ...
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1answer
178 views

can etherscan.io show local ganache transaction details?

I am purchasing tokens on my sample Dapp with ganache-cli account using metamask. Metamask shows the confirm message and deduct the ether from total balance but in token section it still not update ...
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1answer
27 views

How can i make payment application using the blockchain? [closed]

i want to make payment based application by scratch using blockchain, so where can i learn from scratch and what are the different component that i should learn to make an application or a website ...
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400 views

web3.eth.getAccounts() returns empty array

I'm trying to get accounts like that: window.web3.eth.getAccounts( (error, accounts) => { console.log(accounts, error) } ); but it keeps returning an empty array. I'm running Ganache and I can ...
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1answer
51 views

How to replace Metamask Pop-Up with my own UI

I was wondering if I can replace the Metamask pop-up with my own pop-up/user interface. Example: Currently on my dApp a user clicks "Buy Token" and a Metamask modal pops up and says the usual ...

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