ConsenSys/smart-contract-best-practices

Discussion of engineering best practices, design patterns and security for smart contracts

adhikarideepak

@adhikarideepak

Can somebody help me to create a small app using smart contract with some UI, except pet shop ?
Help will be appreciated
Thanks

luckyyousc

@luckyyousc

Hello everyone,just created a lottery game as smart contract ,can you give me some advice ? see more http://luckyyou.io

Lee Raj

@lerajk

@adhikarideepak depends on your use, with some applications it makes sense to store data with a database & call the required functions from the smart contracts with an API like web3 or ethersjs. But if you are looking to bypass SQL/NoSQL databases check IPFS. Storage in blockchain is still a big issue though.

adhikarideepak

@adhikarideepak

Thanks @lerajk , for your this information, I will check IPFS once

cryptogee

@cryptogee

Anybody know how to create a parent/child function within a contract? Example: Crowdfunding app - Function: createCompany (parent) Function: createToken (child)

Maurelian

@maurelian

@cryptogee I don't know what you mean, but your best bet is probably to read the inheritance section: https://solidity.readthedocs.io/en/latest/contracts.html#inheritance
the 'super' keyword might be relevant to you

Laxman Tukadiya

@laxman810_gitlab

Hello everyone

can anyone help to get some simple tutorials for smart contract with front-end and database DAPP ?

Peteris Erins

@Pet3ris

What are the state-of-the-art approaches today to understand why a transaction was reverted?

Anubhav Gupta

@array-addu

Need to create a contest app, where many contests will run parallely and there will be N no of players in each contest. There is also joining fee and winning amount for every contest. What is the best to design the contract?

Michael Rice

@mrice

@Pet3ris - the truffle debugger is getting there

Makoto Inoue

@makoto

Hello. I just wrote a blog post of auditing my own smart contract. Hope this is helpful to the audience here https://medium.com/@makoto_inoue/self-audit-a-new-bug-and-call-for-community-auditing-of-blockparty-e774a8596496

Maurelian

@maurelian

Thanks for sharing @makoto!

Makoto Inoue

@makoto

Hopefully people can learn from my stupid mistakes...

lpw

@lpwlpw

Thanks

Jimmy987

@Jimmy987

``` (shift+enter for line break)

var gas = await commitFunction.EstimateGasAsync(
platformAccount.Address,
new Nethereum.Hex.HexTypes.HexBigInteger(15000),
new HexBigInteger(Nethereum.Util.UnitConversion.Convert.ToWei(0)),
id.HexToByteArray()).ConfigureAwait(false);
```

```var gas = await commitFunction.EstimateGasAsync(platformAccount.Address, new Nethereum.Hex.HexTypes.HexBigInteger(15000), new HexBigInteger(Nethereum.Util.UnitConversion.Convert.ToWei(0)), id.HexToByteArray()).ConfigureAwait(false);```

I wanna estimate gas, but got error: gas required exceeds allowance or always failing transaction.

It work fine at last week, but this week it works error, it so confuse to me.

Jimmy987

@Jimmy987

Can anyone help?
Thanks

kashifaa

@kashifaa

Hi Everyone

I am trying ethereum-login example from https://auth0.com/blog/an-introduction-to-ethereum-and-smart-contracts-part-2/

After doing all steps successfull when I try to execute contract , there is error TypeError: LoginContract.LoginAttempt is not a function

Contract is unable to find its method , what can be possible mistake here ...

or can some body give me some example about new web3.eth.Contract(jsonInterface[, address][, options])

Micah Dameron

@chronaeon

Jimmy and kashifaa, this is a channel for best practices discussion. You're not describing best practices, but asking for help with arbitrary behavior in your own code. Please ask your questions in the ethereum/solidity gitter

Anubhav Gupta

@array-addu

I have a requirement where we need to save data(pdf) to blockchain so that any third party can access and view it later by the block address. I can't store the hash of the data on blockchain as the third party does not have access to the original document to verify the hash of the data. Is it feasible?

Foluso

@foogunlana

@array-addu I often see people store data on IPFS and then hashes in the blockchain. But I'm not completely clear on what the problem is. Do you just need data storage? IPFS, Swarm and other solutions exist for that. Or are you trying to restrict access by some permissions or authorization

Wappnet Systems

@WappnetS_twitter

Hello Everyone

I need Help to implement whitelist addresses contract in my existing smartcontract

anyone can help me ?

Yasin Shuman

@yshuman1

hey all, is there a channel dedicated to testing contracts?

Maurelian

@maurelian

@yshuman1 not to my knowledge, but consensys/truffle will probably discuss testing a fair bit

Nico Vergauwen

@kyriediculous

Anyone familiar here with inline assembly? I've tried like everywhere.
I'm trying to make a low level dispatcher. What is different from existing implementations is that I Need to load in a struct from storage to pass as a param to the library I'm delegating to. I'd also need to split the calldata and put that storage struct in between.
Here's the issue on github: ethereum/solidity#4854

Any help gets huge kudos in my extensive blogpost on smart contract architecture :)

You might ask ,why don't you just write functions that delegate to the library directly without assembly? Because that doesn't save any gas despite many people thinking it does. Making this issue work would reduce deployment gas cost of instances delegating to the logic of the library by more than half. This has enormous positive implications for example identity, where it becomes way cheaper than the current price of 0.30$ to deploy the uPort contract.

Maurelian

@maurelian

@kyriediculous the best resource I know of is the solidity documentation.
You might find this bytes library a useful resource: https://github.com/0xProject/0x-monorepo/blob/development/packages/contracts/src/2.0.0/utils/LibBytes/LibBytes.sol

Anubhav Gupta

@array-addu

I need to store and retrieve multiple values in key value pair, can someone suggest me the best way to achieve this?

Amol🕶

@Amol_Sharma_twitter

Hi I am new here, anyone has a "best practices for smart contract" link/URL/document?

ThisIsCodeXpert

@ThisIsCodeXpert

@Amol_Sharma_twitter checkout this channel : https://www.youtube.com/channel/UCb3Rrg2t4PZ59Sna497DUZA?sub_confirmation=1

Amol🕶

@Amol_Sharma_twitter

Thanks @ThisIsCodeXpert

Devashish Tomar

@dev1644

Hi There,

Can I ask a question about Crowdsale Contract?

Devashish Tomar

@dev1644

How can I link the price of a token to a fiat Currency in Smart Contract.

Aside Oracle can there be another approach to it ?

Shashikant Soni

@shashiks

@dev1644 Since fiat prices are not available on Blockchains. Your best option is an oracle. No I haven't heard of any alternate approach around this

Devashish Tomar

@dev1644

Ok , I knew about oracle approach , want to know if there any other way to do this. Anyways Thanks Bro.

ArsenKulikov

@ArsenKulikov

Hello, Guys! I'm trying to deploy my contracts in mainnet using truffle and infura ws. With ropsten testnet it works perfect, but i had many issues, trying to deploy in mainnet. Finally, after many fixes, all my migrations successfully ended. But last running migrations end on 'Saving successful migration to network...' . Aaaand - nothing. I see it in my console about few hours and nothing happens. Can someone help me, what is this can be?

SatoshiSon

@Thirdwizard

Hi, can someone same me a sample of how to build ERC20 Token with function:
Lock Airdrop Distribution till after Token Sale and Distribute Automatically to members, Distribute Token to Investors automatically, Only Core Investors are required to sell tokens on the first seven (7) days
after listing of Token on Exchange market.
Reserved Tokens locked for 6 Months. Lock Team Member tokens for 12 Months.
Presale and Crowdsale Tokens are distributed automatically to buyers ETH Address,
and locked till After Token sale and 7 days after listing on Exchange Market. Token Sale Prices: $0.001, $0.005, $0.01, $0.05, $0.05
Unsold tokens to be burnt, after crowdsale. If tokens allocated to a particular tier are not exhausted in sales, it should be rolled over progressively to the next tier.

Thanks for the Help

Amol🕶

@Amol_Sharma_twitter

Hi, I am using web3j to deploy contract. Does anyone know how to listen to events on the deployed contract using Infura?

Ankit

@a4nkit_twitter

Hello, can anyone give working issue permission for https://github.com/ConsenSys/smart-contract-best-practices/blob/master/docs/about/contributing.md

also, while deploying on local this time I am getting TypeError: unhashable type: 'dict' error

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