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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119 views

How to choose between Ethereum, EOS, and TRON if I want to build a dapp? [closed]

In 2018, Ethereum dapps has $2.6 Billion worth transaction volume in 2018; EOS has $3.45B; TRON has $600M. However, number of transactions on Ethereum is way less than EOS and TRON. Ethereum has a ...
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1answer
47 views

Execute smart contract only if the wallet contains some tokens [closed]

i created an erc20 token and i'm trying to create a smart contract that stores some informations in a blockchain just if the wallet contain my tokens. How can i do this? Have i to work on the token ...
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0answers
228 views

Sign a transaction locally and send it

I'm using Infura as my web3 provider, and have MetaMask installed to connect to the blockchain. I'm trying to send a transaction, but have learned that Infura is read-only, and doesn't support the ...
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1answer
315 views

web3 Uncaught TypeError: Cannot read property 'createBox' of undefined

i'm trying to create simple application by using solidity 5.0.0 , Truffle v5.0.0 and web3 web3@1.0.0-beta.34. but i've gotten Uncaught TypeError: Cannot read property 'createBox' of undefined. ...
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1answer
294 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
22 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
21 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
147 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
56 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
37 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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2answers
321 views

Deploy multiple instances of same contract

I am developing a decentralised notary app, using truffle/web3/react. It need to deploy multiple instances of a same contract. I managed to deploy multiple instances of a contract, MyContract via a ...
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1answer
27 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
587 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
62 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
210 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
97 views

How to evaluate effectiveness of a Dapp

I am developing a private ethereum-based DApp and writing an academic paper for a final year project. I'm trying to "blockchainify" an existing system that adopts a traditional client-server approach. ...
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1answer
81 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
40 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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0answers
40 views

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
160 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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1answer
399 views

How to get only past 2 days events using getPastEvents everytime?

How can the following query be modified to only fetch the past two days worth of events: const events= await MyContract.getPastEvents("eventName", { fromBlock: 0, toBlock: "latest" });
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2answers
74 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
498 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
28 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
72 views

Calculating a minimum entry fee for a game based on typical minimum gas requirements?

I am creating a dApp that is a game where players compete for the prize pool and that pool is built from the sum of all the entry fees payed by the player at the start of the game. The player that ...
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1answer
218 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
71 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
376 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
649 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
213 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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1answer
23 views

Can Dapp respond to an API evocation which in turn calls an EOA and then evoke a contract?

Can a Dapp (leveraging web3.js) respond to an API evocation from an external system which in turn calls an EOA and then evoke a contract on the blockchain? External system calls a Dapp Dapp calls a ...
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0answers
219 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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2answers
357 views

ecrecover in solidity returning null address [duplicate]

I need help with Ethereum address verification. I'm following the tutorial on signing and validating Ethereum address. GitHub code. I'm confused by my actual result of the address after I ran ...
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0answers
241 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
110 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
631 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
114 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
63 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
236 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
61 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
149 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
23 views

Can a Coin be liquid during its ICO period?

I am planning to run a Coin's ICO for several years, not interested in the gains to be made from selling out ICO in 3 days NO, but interested in using the COin to end Global Poverty as i deem fit. So ...
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1answer
299 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
526 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
440 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
446 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
76 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
60 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 ...