ConsenSys/smart-contract-best-practices

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

Vishal Waman

@VishalWaman

Hi,

We are using https://mainnet.infura.io/ with our Web3.js to listen events from Ethereum
we receive almost 90% or events but 10% are never received

Can anyone guide us on this ?

Thanks

Micah Dameron

@chronaeon

@apbendi , it's best to explicitly mark the visibility of your functions in callouts and state variables.

@VishalWaman did you try the Infura gitter channel?

Ben DiFrancesco

@apbendi

Thanks @chronaeon , here’s my very simple contract. Note I have a public method for returning all contract state, as opposed to marking each property as public. Do you see a downside to this: https://github.com/apbendi/hodl_wallet/blob/master/contracts/HodlWallet.sol#L20

Maurelian

@maurelian

@apbendi security wise, no downside. Possible downside is interoperability, ie. if other contracts want to get one or two values, they'll pay a bit more gas and have to handle the 4 return values. Cost of making all those values public is just a bit more bytecode to deploy.

Ben DiFrancesco

@apbendi

Thanks @maurelian, these all make sense. Just wanted to make sure I wasn’t missing anything else :)

ilbhaicnl

@ilbhaicnl

Hello, I have a smart contract and when trying to initialize it in a website, the address' for the token and token sale wont initialize, I am a newbie so any help will be appreciated! ( solidity, web3js )

lamle

@lamlephamngoc

hi, I got this error message when I tried to truffle migrate my contracts to ropsten today

Error encountered, bailing. Network state unknown. Review successful transactions manually.
exceeds block gas limit

anyone got this message ?

I deployed successful few days ago

sorry for asking this question here, but I don't know where to ask such as this question :(

lamle

@lamlephamngoc

it seem to work now :( sorry everybody here

Mayuresh Khalane

@MayureshKhalane_twitter

Hello.. m facing a problem. When i try to compile Webpack using truffle it says :- Error couldn't find the module 'babley-register' .. please help

Maurelian

@maurelian

People, there is a truffle chat room: https://gitter.im/ConsenSys/truffle

Micah Dameron

@chronaeon

adhikarideepak

@adhikarideepak

Hi All
is there any concept where we can use any database (like mysql or postgress )with smart contract or blockchain?
if yes how can I implement it ?

please share your views

Thanks

Nick Mudge

@mudgen_twitter

Does anybody have some insight about the question asked here: https://ethereum.stackexchange.com/questions/52258/what-are-good-specific-reasons-the-onerc721received-function-returns-a-magic-val

cryptogee

@cryptogee

Does anybody know how to resolve the url not parseableFile.sol error in remix? Am trying to create a child file and remix won't compile, am totally stuck.

@mudgen_twitter Sorry, would love to help but that is way beyond me at the moment.

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

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