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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499 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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1answer
34 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
30 views

Error creating contracts on Ethereum wallet. Need help [duplicate]

I am trying to create an ERC20 token off of ethereum, but when I put the code in the editor in the ethereum wallet, I get a weird error. It says: "throw" is deprecated in favour of "revert()", "...
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2answers
168 views

Creating a simple DApp [closed]

I want to implement the "Decentrilized Gallery", and implement it to the blockchain(ethereum) and it's kinda will work like: Basic html page with a button in the middle to choose a picture from ...
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1answer
91 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 ...
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1answer
48 views

Execution of sending transaction never ends [UPDATED]

I send a transaction with web3 1.0.0 from a script like: async function sending(deployed_contract) { await deployed_contract.methods.mymethod(1).send({from: account}) .on('...
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1answer
32 views

Which type of Projects/Apps are suitable/best to be developed in blockchain/dapp technology? [closed]

Which kind of Apps are best to be developed on the base of blockchain/dapp/web3 technology. Suggest me please as I am looking for an advice for an academic final year project.
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1answer
860 views

Calling a “view” function using web3js

--- HEAVILY EDITED --- Solidity contract: pragma solidity ^0.4.24; contract PatientRecords { struct Patient { string ID; string weight; string height; string diseasehistory; ...
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1answer
71 views

copy etherdelta code [closed]

For a test project, I need to write the etherdelta's contract. but "function EtherDelta (address admin_, address feeAccount_, address accountLevelsAddr_, uint feeMake_, uint feeTake_, uint feeRebate_) ...
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1answer
244 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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1answer
93 views

How to catch Out of Gas exception in Oraclize Callback and display error on dapp front end

I have a smart contract inside which I have used Oraclize to get current time stamp. On few occasions the Oraclize callback fails due to out of Gas exception. How can one catch this failure and ...
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1answer
57 views

Is it safe to have a locally running Ethereum node exposing personal RPC API? [duplicate]

I am developing a REST API currently running off a node.js server. The API allows ethereum account creation, making a transaction etc. The API interacts with a locally running ethereum node to ...
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Dapp design to handle delay in callback response from Oraclize

In my dapp design I am receiving few user inputs via a form and passing them to a smart contract. Inside the smart contract I am using Oraclize service to timestamp the user inputs. Its a known fact ...
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2answers
222 views

ERC721 Dapp not working, not showing token owner

So I am building a Dapp to interact with an ERC721 contract. So far I'm able to mint, transfer and check an address balance. I'm stuck with trying to show who owns which token( via their token id). ...
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2answers
96 views

Checking if Contract Withdrawal Is Allowed

I am trying to conceptualization how a specific kind of smart contract would be written. The contract would basically handle deposits and withdrawals of ETH or some sort of ERC20 token. The balances ...
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1answer
565 views

Thoughts about implementing masternodes in a ERC20 Token

I am developing a cryptocurrency on top of ethereum blockchain that will have some sort of rewarding features for the large hodlers of the coin. I know two ways of doing that: Airdrop - like Pundi X ...
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1answer
40 views

Issues with transaction signing

I have a desktop app that accepts payment from user in ETH and provides it some service for a certain amount of time depending on the amount. For that the user needs to sign the transaction in the ...
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1answer
243 views

Beginner - Design pattern for a hybrid dapp

This is the first dapp I'm going to build and I was thinking about not doing it 100% decentralized due to some limitations I've been encountering with Solidity (This may just be because of the way I'm ...
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1answer
84 views

Can somebody check my understanding of DApps and Smart contracts

can somebody check my understanding on DApps and smart contracts in general? (Please excuse the long winded-ness I’ve only been reading about DApp’s for 3 days now so I’m very new and I’m kind of ...
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0answers
471 views

How to use MetaMask Web3 with Truffle promises

My project uses the react truffle box, and I use the getWeb3 method that comes with it. After calling that method, I store the web3 object on Redux's state tree via the action creator storeWeb3. ...
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1answer
990 views

Input data on Solidity

I'm trying to do something simple like Hello World that shows on a webpage. I've written a smart contract like this: pragma solidity ^0.4.18; contract HelloContract { string word = "Hello World!"...
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3answers
2k views

calling smart contract functions from app.js

I deployed a smart contract to ganache network using truffle from account1. The code of smart contract is as follows. pragma solidity ^0.4.0; import "./strings.sol"; import "./safemath.sol"; ...
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1answer
271 views

How fast and scalable is a Dapp build on ethereum?

I am a beginner to Dapps on ethereum and smart contracts but I wanted to ask three questions on building on top of ethereum. Firstly, how fast would an Dapp with a token will the transactions per ...
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222 views

How to deploy a Smart Contract in Ethereum on Azure?

Iam trying to deploy a smart contract in Azure's Ethereum on Azure. I have created a blockchain in that but now I need to deploy a smart contract and design a UI for the same. I want to use Remix to ...
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0answers
264 views

In truffle Console Works, but when called in Javascript, Metamask hangs, Solidity contract doesn't update

So I have a function where I am asking the user to send two strings and 1 ether at the same time. When I execute the function in the console, the solidity contract is updated. When I execute the same ...
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1answer
124 views

Serving DApp on webserver or IPFS won't work

I can succesfully run the webpack truffle box on my webserver, but if I try to run a DApp which I made by using the pet-shop truffle box as template, I can only use it on localhost. When I upload the /...
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3answers
735 views

Create a DApp using Geth

I need to create a sample DApp from scratch within a private blockchain using Geth. Can anyone post links of sample apps which have been made in such a way for reference.
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1answer
121 views

Would the users still need to use Metamask or Mist if the dapp has a built in wallet?

If a dapp has a built-in wallet, can the users intearact with the dapp without the need of Metamask or Mist?
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1answer
70 views

Is there a solidity library to create msgHash?

Messages are hashed with a “\x19Ethereum Signed Message” for some reason. I'm writing a smart contract that authenticates a message to a signature, and it needs to be able to generate msgHash to do ...
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1answer
284 views

Correct way to easily call function with web3j from deployed contract

I am trying to call a function from a modified ERC20 contract and I can't manage to make it work. I am doing this with web3j from Android. I can connect to Infura. The contract is already deployed on ...
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2answers
98 views

If I wanted to host a site that used the web3 api, would I need it to interact with the blockchain?

I want to host a site to interact with Web3 clients (MetaMask, etc.). I want my site to be able to send transactions, etc. to the clients through the Web3 API for educational purposes. I don't care ...
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1answer
168 views

Environment to run Daap

I already run test apps online on a rinkeby test network and have a good understanding of how to dev and publish my apps on this particular blockchain. HOWEVER, I have been in trouble understanding ...
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1answer
317 views

Factory Contract Function is not creating New Contract using testrpc and web3

I am new to DApp development. I have deployed a TokenFactory contract and that Factory contract has a function "Create New Token" that generates a new token contract. The function "Create New Token" ...
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1answer
576 views

Deploying Solidity Contract Using Web GUI and web3

Any guide or step by step Tutorial for deploying a solidity smart using a GUI and accessing the meta mask account ? Please Help
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2answers
540 views

Deploying a smart contract using DApp

I am new to the development of DApps on ethereum blockchain. I want to make a contract Management System in which users can generate their own tokens and crowdsale using my web application. I am able ...
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1answer
2k views

Where can I start learning to develop Decenteralized apps? [duplicate]

I have been trying to understand this development process of making DaPPs using ehtereum from various sources, some of them are outdated because this technology is evolving pretty fast as of now. ...
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1answer
521 views

How to get all my users stored in a smart contract in aim to display themn into a Dapp?

Let's consider the following: struct SkillStruct{ bytes32 skillName; uint index; } struct UserStruct { bytes32 userEmail; bytes32 userFirstname; bytes32 userLastname; uint index; uint ...
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1answer
98 views

Code to check if address have received token? [duplicate]

Please I am currently learning how to build dapps and I need a code that checks an address to see if a token payment have been receive... Anyone please?
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2answers
74 views

Can I restrict new users to create a password and then access their data next time by only passing the password and getting validated? (Solidity)

I am trying to build a Dapp for healthcare where I must be able to allow patients(users) to enter their details after creating (say an account) by a password and next time they are able to view their ...
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1answer
290 views

Update dapp after contract transaction is mined

I made a web app that interacts with a smart contract, using truffle unbox webpack. My contract has a variable called sum and 2 functions: one called answer that increments the sum variable after it ...
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2answers
540 views

What is ETH useful for appart from being a cryptocurrency? Does it have something specific due to smart contracts? [duplicate]

It seems the main cryptos are divided into (very roughly) two parts: the original plain blockchain-based cryptos such as BTC, BCH, LTC... on one hand, and ethereum on the other hand which allows the ...
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2answers
133 views

Solidity opcode error when sending coin to an address

So I get the error below when attempting to send the coins to another address, and with the debugger, I can't figure out where's the problem. What am I doing wrong? (I just started learning solidity a ...
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2answers
890 views

How to use a private network in geth?

I am following this answer: How do I set up a private ethereum network? but my result of miner.start() will return null Is it because my geth version is 1.6.6-stable? Also welcome any beginner's ...
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1answer
182 views

DAPP Gas Fees, how often is it charged?

Do you have to pay gas each time you deploy a DAPP and if so does that mean you have to pay gas for updates as well?
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0answers
55 views

Regarding Packaging of DApp

By now I have tried developing a few contracts, deploying them to a test network and using a Javascript based web application to connect to the contracts and use them. What I want to understand what ...
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0answers
836 views

'Web3' is undefined in html javascript

I have geth installed and running and I am connected to a private network. As given in https://github.com/ethereum/web3.js, I have created a test html with jquery-3.1.1.min.js and web3.min.js and then ...
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1answer
40 views

How to search for a dapp based on its address?

There are many websites that track dapps like http://dappradar.com or https://www.dapp.com. Unlike Etherscan one particular dapp doesn’t have to be registered on such specific website in order to be ...
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3answers
384 views

condition check of struct mapping in solidity?

struct User { string username; string password; address userid; bool isAdmin; } mapping (uint => User) users; function checkIfUserExists(address userid) public ...
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3answers
842 views

How do Dapps work with ERC20 tokens?

I just finished reading which explains how to build a Dapp with Metamask sending Ethereum to a smart contract (Reference: https://medium.com/@merunasgrincalaitis/the-ultimate-end-to-end-tutorial-to-...
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1answer
659 views

How to deploy a truffle built Dapp

I've completed my truffle Dapp, the contracts are deployed to the Ropsten test network and my web code talks nicely to them, it works great from http://localhost:8080/ when I do an npm run dev. I now ...