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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1answer
2k views

How to pass an array as the function parameter?

I meet the same problem as this question: Passing an array as a parameter from javascrpt (web3) to a Solidity function If I call my function in the browser-solidity with the parameter [122,44], it ...
2
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1answer
349 views

Need an example to make a state variable reactive in Meteor

I'm having trouble properly understanding Meteor's reactivity and it's relation to contracts. I've included the Ethereum Meteor packages ethereum:web3 and ethereum:blocks and read that EthBlocks....
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5k views

Building Web based UI for Smart Contract

I am struggling to get some tutorial on building web based UI to interact with smart contract. I found examples on using web3 but it uses localhost:8545. However, my understanding is that web based UI ...
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1answer
880 views

Ethereum Wallet: error of no key for given address or file

In etherum wallet I am getting an error of no key for given address or file during deployment of the contract. What will be the reason for the same? contract User{ string public userName; ...
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0answers
77 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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0answers
38 views

How shoud I properly initialize DApp and get account address?

I am writing DApp in react, and basically I want to initialize web3, unlock account, and display it. Having web3 in my package.json In the onload I've tried to go following: let Web3 = require('web3')...
2
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0answers
27 views

Suck at JavaScript and overall just a beginner in the dev world. Whats the best way to begin building DApps? [closed]

Suck at JavaScript and overall just a beginner in the dev world. Whats the best way to begin building DApps? The title is my question LOL.
2
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1answer
193 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 ...
2
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1answer
26 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. ...
2
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1answer
241 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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0answers
891 views

web3.personal.newAccount() successfully created but not listed in ganache accounts.why?

I am using truffle framework for Dapp development and I am new in Blockchain.I used the command web3.personal.newAccount() to create a new account. But i cannot view this account when i take ...
2
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1answer
247 views

Calling function from another contract reverts

I've been developing a dApp that needs ERC721 tokens. I have three contracts, a base contract, the one to mint tokens and another one for auctions. The inheritance looks like Base > Token > Auctions. ...
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195 views

Decentralized File Storage on Ethereum white paper

I am reading white paper of Ethereum, and I am confused by this example of the Section. Decentralized File Storage, which is part of the Section. Applications: The key underpinning piece of such a ...
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2answers
565 views

Detailed tutorial for DApp programming [closed]

I am new to node js and I tried to follow some tutorials to understand it. But, when I started writing DApp code, I get lot of errors like this (calling smart contract functions from app.js). I face ...
2
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1answer
237 views

Does it make sense to have a Node.js backend serving json to frontend for dapp?

Currently, the architecture I am looking at is that the smart contract (SC) sits on the ethereum network, but it is a complex and multilevel contract system. Just navigating through the tiers of the ...
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2answers
184 views

Mining, Ethers and Private Blockchain DAPPs

I am building a private Blockchain cluster DAPP envisaged to have 5 to 10 parties owning their own nodes (or node clusters). At this moment, there is no specific mandate to incentivize miners, though ...
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0answers
595 views

What is the best practice of a Dapp development mixed with Python/Django?

I've written and tested the Smart Contracts in Truffle, and now want to develop a front-end and a small back-end for my Dapp. So far, I preferred MVP frameworks, particularly Django. Therefore, what ...
2
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1answer
242 views

Can i delete some old files inside chaindata folder?

I am running geth with fast sync, Can i delete some old files inside chaindata folder so that my ssd will have some empty space or it will create some problems ?
2
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1answer
203 views

How do I get access to uPort from a mobile Browser

I've developed a simple DApp that uses uPort and it works fine on Desktop - where I can login through uPort with the QR Code. On a mobile browser (Anrdoid Chrome) I'm auto directed to uPort where it ...
2
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2answers
2k views

Diffrent between smart contract and dapp [duplicate]

I struggle with the following questions about definitions. Is a dapp just the implementation of a smart contract? So when someone says he is writing a smart contract he is actually writing a dapp? ...
2
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1answer
765 views

How to find bootnode IP Addresses for Ethereum testnet (Ropsten and Rinkeby)?

I am trying to develop a simple Voting app by following a tutorial on the net. I want to deploy my dapp to the testnet. To do this I am using the bootnodes as mentioned in the tutorial (below), but ...
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0answers
404 views

Send transaction with metamask and web3

I'm new to the topic but can I somehow sendTransaction via contract instance? What I'm missing here? I simply want to send some ether to contract. var abi =[ { "constant": true, "...
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2answers
129 views

Possible to search swarm or blockchain?

I'm getting my feet wet in this blockchain world and looking to build a dapp based on Ethereum for maintaining an inventory of products. About 400,000 items that can be updated, removed or added to by ...
2
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1answer
254 views

How do I capture a smart contract function return values when changing the contract status? [duplicate]

pragma solidity ^0.4.6; contract Demo { uint a; function set(uint b) returns (uint) { a = b; return a * b; } function get() constant returns (uint) { return ...
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0answers
52 views

show specific information to specific users in meteor dapp

if a have a dapp with different users, and each user has his/her own profile page they can log in to. On this profile page, the user should be able to change/add his user information (name, age, etc) ...
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0answers
34 views

How to return form data from an EthElements.Modal.question?

I'm trying to process data from an EthElements.Modal.question, however no event is passed when OK is clicked and this just points to the model call data and not the Template content.
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0answers
67 views

How do I edit a contract already in the blockchain? [duplicate]

I have a contract currently in the chain and I want to add a feature. Do I need to make a brand new contract, or is there a better way? And if I have registered the contract with a name can I ...
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0answers
62 views

Why does Mist doest show up anything for me running on testnet

I just see a blank screen when I open Mist Browser on ubuntu running on testnet. What is the issue ? I couldnt start in the first place. But after using --ignore-gpu-blacklist I could start, Then I ...
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3answers
325 views

comparing two addresses

I'am trying to create a modifier that allows certain accounts to execute functions. address[] authorized; function verify (address adrs) internal view returns (bool) { bool exist; ...
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2answers
243 views

How are truffle artifacts different from ABI?

How are truffle artifacts different from ABI? Do Truffle artifacts include fields that are different from ABI that is generated using remix?
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3answers
5k views

How to generate Private key, public key and address

I can't find any documentation online about doing this in Javascript other than this. I want to know how does authentication work in a ethereum dApp's.. As per my understanding user seed somehow gets ...
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2answers
6k views

What are the advantages of creating a dapp over a normal web application?

A lot of dapps seem like nothing new to me and the added benefit of creating a dapp seems very minimal besides decentralization.
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3answers
3k views

Cannot connect to Parity from browser UI

I am not able to connect to Parity via the browser UI. I have tried multiple times with different tokens generated by running the command parity signer new-token on the node where parity is running. ...
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3answers
154 views

a question about oraclize api

anyone know how oraclize api is working. I read the source code files on github.com/oraclize/ethereum_api . it need a "__callback" function in my contract to receive the result, is it means there has ...
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3answers
981 views

To run a dapp is it required to download the full blockchain?

In this article https://medium.com/@mvmurthy/ethereum-for-web-developers-890be23d1d0c the author writes that This means, every person who wants to interact with a dapp (Decentralized Application)...
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1answer
396 views

Is it possible to embedd the UI of DApp in the blockchain?

I have read the answers for this question as well as their linked resources, but I didn't found the answer for the following question: is it possible to embedd the UI of ÐApp in the blockchain? If I ...
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2answers
456 views

How to create a multiple contract with multiple instance

I would like to know how to create (via another contract or something else) several instances of the same contract with different parameters. For example create several different ERC20 on demand with ...
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3answers
168 views

Transfer ethereum

I ran into something weird I can't figure it out. for(uint i = 0; i <= payroll.length; i++) { payroll[i].transfer(0.1 ether + totalPrizePool); } Where: totalPrizePool is some amount of ethereum ...
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1answer
446 views

How can I make a Dapp that is free to use?

I have a dapp where I want users to be able to register an account without needing Ether. Is it possible on the Ethereum network?
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3answers
359 views

From a traditional web based application how can I able to call ethereum network node?

Let's say there is a web application running on server 12.34.45.45 ip. Peer A open this web application in his own browser.Now how he will be able to connect a ethereum node where peer B is running....
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1answer
94 views

I found a useful Ethereum script. How do I run it ELI5?

What's the least painful option to use the Stackexchange Bounty script described here? I'm dreaming of a chrome extension :)
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1answer
1k views

How to read a data sent to my Smart Contract

How can I read/ get a data that has ben sent to my smart contract ? I tested sendTransaction({data: xyz }) and when I tried to get this data from the Smart Contract using msg.data I got NULL this ...
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1answer
40 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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1answer
77 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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2answers
211 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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2answers
456 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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2answers
307 views

How do we achieve immutability within a contract on the blockchain?

Am relatively new to the realm of Dapps and blockchain in general, and if you ask someone well-informed about the characteristics of blockchains, the word "immutable" will invariably appear in the ...
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1answer
2k views

How to map a web3 to a react.js state

How would you map a changing variable from web3 to react.js component? Example: class App extends Component { constructor(props){ super(props); this.state = { blockNumber: web3.eth....
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2answers
376 views

Is web3 a true distributed app?

The web3.js is the most easiest and perhaps the standard way of dapp creation.And there are two providers possible as of now , HttpProvider and IPCProvider. The HttpProvider takes the address at which ...
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3answers
215 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?