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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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1answer
23 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
101 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
54 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
21 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
17 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
34 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
21 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
74 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
32 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
191 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
13 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 ...
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1answer
49 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
119 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
79 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
24 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
42 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
9 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
115 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 ...
1
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1answer
153 views

How to use local Metamask account with Infura Node [duplicate]

I'm building a DApp using web3js that sends ERC20 Tokens from a browser Metamask account to an escrow contract on the Rinkeby testnet. I'm using a Rinkeby node from Infura, and when I call web3.eth....
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1answer
35 views

Problem retrieving array of struct with web3js

I'm trying to return the struct values contained in array everytime i push a button thet call inserimento and ritornavalore functions. here is my code in solidity: pragma solidity ^0.5.1; pragma ...
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0answers
14 views

How DApps solve profiles

I am in the process of designing the architecture of a DApp. I am strugling with the profile module. Just a theoretical question: Is it possible to let users create a free profile or a basic login? ...
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1answer
72 views

Invalid JSON Response while connecting DApp, Metamask and Backend

I am getting some error(picture below) while trying to connect DApp with a backend. One day ago, everything worked fine, now I got an error: "basic auth failure". Contracts are deployed on Ropsten ...
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1answer
35 views

Ethereum with Rails

I am much familiar with Rails but new in the Ethereum. But base on my understanding, if I am going to build a Dapp. The web stack should not include the back-end system like Rails. But why there's so ...
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1answer
200 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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0answers
140 views

CORS policy error while connect to test-rpc

I'm trying to build my first dapp using test-rpc and web3js. I deployed a smart contract (with remix ide) to the testrpc (on linux ubuntu), when executing the following line: web3 = new Web3(new Web3....
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0answers
28 views

transaction not processing

The code below is for selling tokens to the smart contract, the INR_ETH.sellTokens() function calls the smart contract. but the code is not working properly, metamask asks for the "approve" part but ...
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1answer
33 views

Can't create child contract in mainnet?

address[] child; function createChildContract() onlyOwner public{ address newChild = new Child(msg.sender); child.push(newChild); emit ChildCreated(newChild); } contract Child { ...
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1answer
8 views

Function inside constructor is called from which address?

interface token { function transferFrom(address _from, address _to, uint256 _value) external returns (bool success);} contract CampaignFactory{ token public token_instance; constructor()...
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2answers
47 views

Set and Get of a large amount of data

I created a contract that insert one number (uint) in blockchain with set function but how can i retrieve all numbers inserted? This is my html, i put 1 number in a blockchain and i will see just the ...
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2answers
42 views

Returning all struct data of msg.sender in solidity

here is my code: contract Notes { struct notes { string id; string content; address owner; bool isCreated; bool isDeleted; uint256 timestamp; } ...
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1answer
163 views

Remix error: “Expected token LBrace got 'View' function get() public view returns (uint)”

I have this error during the compiling of the code below on Remix. Someone could help me ? pragma solidity 0.4.4; contract SimpleStorage{ uint storeddata; function set(uint x) ...
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0answers
57 views

Problem with Dapp in the browser

I'm trying to develop a voting Dapp, I have already created the Smart Contract and the js and html files. I have successfully migrated the contract into the Blockchain (I'm using Ganache), but when I ...
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1answer
39 views

Best options to host an ethereum react dapp to a custom domain

I'm looking for best options to host an ethereum dapp created using react and drizzle, with the following requirements: It needs to be hosted in a custom domain (.com / .net / OR .io ) that I have ...
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1answer
289 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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2answers
46 views

Including an owner address based automated routine execution in a React ethereum dapp?

As I understand, all the front-end components for a react based ethereum dapp are rendered from the point of view of the user's metamask default account. All the calls to constant functions in ...
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1answer
78 views

Storing User data on blockchain

I am currently using the structure and mapping to store the user data in the blockchain. In the mapping I am using user's address (msg.sender) for mapping it with structure so every user can only ...
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1answer
33 views

Getting error on sending ether/wei in payable function

error: transact to CampaignFactory.createCampaign errored: VM error: revert. revert The transaction has been reverted to the initial state. Note: The constructor should be payable if you send value. ...
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2answers
40 views

How to use function arguments of payable function for require statement?

function createCampaign(uint deposit, address ll) public payable{ dpst = deposit; require(msg.value > (40*dpst)/100 wei); address newCampaign = address((new Campaign).value(msg.value)(...
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0answers
97 views

Login to an ethereum dapp on sending a transaction?

I'm trying to build a sample dapp. The login process in ethereum dapps usually involves signing a message from metamask to prove ownership of an account. Is there a way we could design login in such a ...
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1answer
27 views

creating instance of contract trough a factory contract! Problems with balance!

hopefully someone can help me with my question. I have a factory to create an instance of a dealContract. Everything works except one thing. I cant send wei to the created instance, so lets see the ...
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2answers
87 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
231 views

Simple smart contracts to make a bet [closed]

I would like to create a simple smart contract between me and a couple of friends (basically, I'm putting money on the line and betting them that I will do something that they don't think I'll do.) ...
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1answer
44 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
75 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
60 views

Design Dapp with Kotlin front end

To develop Dapp using Kotlin programming language for the front end design, Where should I place this code? and what it should be changed? <script> // Connect a the web3 provider ...
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1answer
45 views

Stress test DApps on rinkeby test network

Is there any way of stress testing a dapp? I developed dapp, now I want to see how much stress it can handle? I can't test it on Main Ethereum Network. At least I can do it on Rinkeby test Network. ...
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1answer
83 views

Solidity Vs JavaScript?

I'm currently in the process of writing a game however a question has popped up in my head. A while back I started writing my game in Solidity (i.e the characters, names, stats etc.) and I had ...
1
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1answer
331 views

how to upload file into ipfs from node js without uploading files into node js server [closed]

I need to upload multiple files into ipfs from node js. Flow: file(html,angularJS) --> node.js --> IPFS --> ipfs hash save into DB. I have sent a file from HTML(angularJS) and I got the ...