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Questions tagged [dapp-development]

Questions regarding the development of decentralized applications (a.k.a. DApps). This can include everything from frontend development questions to interaction with the blockchain and distributed file storage.

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1answer
19 views

ERC 721 card game

The general concept of ERC 721 is clear to me. My question is more about the contract deployment. I want to have 100 unique cards, So I thought of these two implementations: Having an initial supply(...
0
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1answer
13 views

Miner APIs are not found in web3.js package

How can I start and stop miner( miner.start(), miner.stop()) from my DApp if Miner APIs are available in web3.js package? I am using web3 v0.20.6.
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1answer
9 views

What is the difference between writing emit in an event and not using emit? [duplicate]

For example, event CoinTransfer(address sender, address receiver, uint amount); What is the difference between CoinTransfer(msg.sender, receiver, amount); and emit CoinTransfer(msg.sender, receiver, ...
1
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1answer
10 views

Ethereum Node I want to export transactions from a token

I have an Ethereum node running and I am wanting to export transaction history for a specific ERC20 token to a local database every 10 minutes. Does anyone have any suggestions on how they would do ...
0
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1answer
32 views

Web3 Rinkeby Infura Problems

I've got a Smart Contract that works perfectly when deployed to localhost: 8545 (using Ganache) with my Web3 Dapp. But when I put it on Rinkeby, I'm running into problems,. The Contract is super-...
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0answers
28 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 ...
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0answers
22 views

What is a suitable pattern for building a web/mobile app that leverages ether? [closed]

Noob to ether dev. Looking to understand how to build an app that leverages Ethereum - what suitable patterns are out there (ideally to go via some tutorials). A few apps examples (from easy to ...
1
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1answer
13 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
14 views

How to specify the Gas price for ICO contract

I am writing a ICO contract in truffle using openzeppelin I used the below code in the truffle.js and I am trying to launch in mainnet. When I tried this I could see that the transaction is using the ...
0
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1answer
15 views

DApp on Node2 accessing smart contract deployed by Node1

Node 1(Desktop) deployed a contract on private blockchain. From node2(Laptop),I want to interact with the contract. But I failed at 'web3.version.getNetwork(err, netId)' function.This function throws ...
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1answer
34 views

Creating transactions with Transaction Data to Metamask

We can use transaction data to submit any Ethereum transaction using Metamask, right? Not only ERC20 transfers, right? Does anyone knows how can I generate hexadecimal transaction data to Metamask ...
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0answers
19 views

ParserError: Expected identifier but got 'function' function

I am building a KYC application to record Companies, Legal Representatives etc data. I am getting the following error in Remix: ParserError: Expected identifier but got 'function' function ...
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1answer
21 views

Understand inter-operation between typical DApp and its underlying smart contracts

I am a newbie to Ethereum and start to study some typical implementations of commonly-used DApp. So basically for the popular dapp on this list (https://www.stateofthedapps.com/rankings/platform/...
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0answers
18 views

How Blockapps's REST-API work?

I am new to Blockapps. I am figuring out what is blockapp rest api? There github repo blockapp-rest In the repo the repository they referred were removed. My question is if I write the below code in ...
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0answers
18 views

Where is the latest MetaMask hello world dapp example?

MetaMask recently added a new permissions check. I'd like a copy-pasteable hello world dapp that includes all best practices and can check the balance of the current user's ERC20 balance for some ...
1
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2answers
38 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 ...
2
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1answer
41 views

What is the most active Ethereum chatroom for devs? Slack? Telegram? IRC?

Where does most of the ethereum developers hang out? Slack? Telegram? IRC? I'm looking to join a chatroom where everyone can help others while developing.
2
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2answers
69 views

Unable to install web3 js for windows10

I am trying to install web3 using command npm install --save web3@1.0.0-beta.26 However, it is failing with error : verbose node v8.9.1 verbose npm v4.6.1 error code 128 error Command failed: ...
0
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1answer
31 views

Deploying using Rinkeby understanding

Deploy we are using truffle truffle migrate --reset --compile-all --network rinkeby when i am deploying i will be getting build folder in my project directory while deploying through the ...
0
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1answer
57 views

How to fix “No events were emitted”

I have been following the instructions in the Dapp university tutorial. But I am using Windows 10, Dapp University is Mac. I downloaded this truffle with smart contract ERC20 from Dapp university. ...
0
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1answer
26 views

Is data inputted as a parameter for a smart contract function visible?

Let's say I have something like this: bytes32 person; function registerPerson(address _person) public { bytes32 x; x = sha256(abi.encodePacked(_person)); person = x; } For privacy reasons, ...
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2answers
39 views

Intracting with dapp using frontend truffle petbox

App = { web3Provider: null, contracts: {}, account: '0x0', init: function() { // Load pets. return App.initWeb3(); }, initWeb3: function() { if (typeof web3 !== 'undefined') {...
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1answer
55 views

How to interface with a deployed Ethereum smart contract?

I want to create an interface to interact with my smart contract. I have got an example from the following link. Counter Before implementing my contract, I have tried to use the given example.But it ...
0
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1answer
139 views

web3.js token approve function show null / 0 in Metamask

EDIT The allowance is set, the issue is just that metamask detect no token name nor amount that is allowed. In my HTML/JS amount = parseInt(web3.toWei(amount, "ether" )); tokeninstance.approve(...
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1answer
18 views

Unknown wallet address on private development chain

Apologies in advance for the long post. I'm new to Ethereum and don't know which details are significant and which are not. I'm trying to learn about dapps by following an example in this book. My ...
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3answers
37 views

How to create a smart contract that has token and transfers tokens to whoever sends ether?

I want to create a smart contract which is able to create tokens, priced at some amount of ether, example uint price = 1 ether;. Now after someone sends any amount of ether, the same amount of tokens ...
1
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1answer
58 views

web3js - Promises - web3.eth.getAccounts()

Objective: Assign a global variable to the first indexed address returned in web3.eth.getAccounts(). I want this so I can use it in the rest of my code and simply reference a variable. Problem: ...
0
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1answer
22 views

ContractInstance.method is undefined

When I use contractInstance.getDrawStats or any other method it returns error method is not a function because of contractInstance doesn't contain any contract methods. However, they are definitely in ...
0
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1answer
38 views

Need help in deploying a dapp on Ropsten without truffle

I am trying to deploy a Decentralized application on Ropsten without using truffle (trying to challenge myself), but for now I am stuck at few places, the deploy.js file which is supposed to deploy ...
0
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1answer
125 views

How to write a component in Drizzle React? [closed]

The components are for the following functions: function tokenURI(uint256 _tokenId) public view returns (string) { require(exists(_tokenId)); return tokenURIs[_tokenId]; } function ...
2
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0answers
36 views

ICO for a startup I am planning to build but have some questions [closed]

I am an software developer with over 11 years of experience in industry and has worked as a software developer for some of the leading firms in vacation rental space. I recently started playing around ...
0
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2answers
92 views

How to decode data parameter under logs in transaction receipt?

I went through many questions but I couldn't get my answer. web3 version -- 0.20.6 According to documentation event's parameters which are not indexed store in data parameter under logs. I want to ...
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0answers
18 views

k-d tree in solidity for efficient search operation

Let us consider the following example contract Courses { struct Instructor { uint age; string fName; string lName; } mapping (address => Instructor) ...
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1answer
68 views

Why no dapps in the Google Play Store? Why Ethereum not accessible by default in smartphone?

Before I create a decentralized application, I want to know whether it already exists. I thought the first step would be to search the Google Play Store, but it appears dapps are not available on the ...
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1answer
61 views

CappedCrowdsale of mintable ERC721

I am thinking of building a capped crowd sale using CappedCrowdsale and MintableERC721 of OpenZeppelin. I wonder if its better to mint the tokens once the cap is reached or to mint seperately once a ...
2
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1answer
54 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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1answer
59 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?
2
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1answer
173 views

Login system for DAPP without metamask

I'm building Dapp on Ethereum. Imagine I have companies to register in my dapp, I will provide them with their own smart contract and public and private key pair, which they will use to just unlock ...
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3answers
109 views

Login system for DAPP

I'm building Dapp on Ethereum. The main feature of this Dapp is Register/Login logic. I Don't want to use Metamask, but I want to make Login system like MyEtherWallet without any chrome extention. ...
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0answers
71 views

Consuming rpc url in metamask and in remix web3 provider

Tried to use the Rpc url(created at end of aws ethereum templates) in metamask/ remix ide(injected web3/ web3 provider). Also, got 5 accounts addresses(from initial list of accounts while creating ...
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2answers
73 views

Input from IOT devices direct to the smart contracts?

I went through almost all the answers on IOT but not got the answer. I want to create a DAPP which takes temp as input from IOT device and trigger function in the smart contract. I know the options ...
2
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1answer
46 views

web3 1.0 in production

I have been using web3 1.0 (v26-beta) in the development of my dApp without errors. The smart contracts are already on Rinkeby and I intend to deploy them in mainnet in a near future. Are there ...
2
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2answers
82 views

Problem using require('ethereumjs-tx');

I am making a dapp and I am trying to import modules. The structure of my folders is the one that you can get from the truffle webpackage, the following: -App ---build ---constracts ---migrations ---...
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0answers
19 views

Understanding Solidity Libraries using Solidity Docs code example

I was going through this code (see code below) about how to use libraries in solidity docs : https://solidity.readthedocs.io/en/v0.4.24/contracts.html?highlight=library#libraries and there are some ...
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1answer
29 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. ...
1
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1answer
83 views

Implementing Blockchain and Converting Web App to DApp

I have my web-application which is in Angular2 (Front end) and Rails (Back end-API), now I want to implement Blockchain to this Web application, so needs to make it DApp. Here while making the DApp, ...
1
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1answer
103 views

How to access metamask accounts when using Infura Websockets

I am making a dApp where in for login purpose I access metamask account to which user is logged in. I also have a back end server that listens to events emitted by the smart contract that updates data ...
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1answer
21 views

How to use require() with stings

I am trying to run this code on remix IDE: pragma solidity ^0.4.24; contract Aa { string public result; function feedData(string _result) public { require(_result = "e" , "...
1
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1answer
16 views

how to use the logical operator “or”

I am trying to implement a simple smart contract on Remix IDE (using Genache as my local blockchain) Here is the code: pragma solidity ^0.4.24; contract Aa { uint public myuint; function ...
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0answers
21 views

How to run a dapp with a backend server on Rinkeby Network [duplicate]

I have created a dapp which has a front end as well as a backend server. The role of back end server is to listen to events triggered by the smart contract and execute related piece of code. So far I ...