ERC20 internal transfer method

[k06a]

🚀 Description

Allow ERC20 subclasses to perform transfers with own rules. For example by providing senders signature or something else.

Just extracted common transfer and transferFrom code into internal _transfer method.

• 📘 I've reviewed the OpenZeppelin Contributor Guidelines
• ✅ I've added tests where applicable to test my new functionality.
• 📖 I've made sure that my contracts are well-documented.
• 🎨 I've run the JS/Solidity linters and fixed any issues (npm run lint:fix).

[nventuro]

Interesting, I like this! I wonder why we didn't do it before?

Note that this will become part of our public API, and as such will need to wait until the next minor release.

[frangio]

Yeah I think this makes a lot of sense to have.

@k06a I'm curious, have you run into the need to use this?

[k06a]

@frangio @nventuro I browsed the latest version of ERC20.sol and decided this API was missed. Some token creators would like to provide token transfers based on holder signatures for example.

A while ago I developed the library for this: https://github.com/bitclave/Feeless. Do you think this kind of functionality could be included in openzeppelin-solidity library?

[k06a]

@frangio @nventuro what do you guys think of this line?

require(value <= _balances[from]);

I am sure this overflow check is already exist in this line:

_balances[from] = _balances[from].sub(value);

It seems we can save some gas.

[frangio]

The redundancy in those lines has come up before, but if you feel we need to revisit the discussion please open a different issue.

Feeless is super interesting! I'm interested in providing stuff like that in OpenZeppelin in the future, but I personally don't see it in the roadmap very soon.

Thanks @k06a!

[ardagokcek]

@frangio I think line 98 must be after line 99. When someone edits the _transfer function and doesn't uses require or revert, then line 98 will decrease the allowence but line 99 won't make the transfer.

[k06a]

@ardagokcek I think changing this lines order will not help in this case. You mean someone overrides _transfer? It should revert in case of failure. I used this order of lines because of order of lines 207-209.

[ardagokcek]

Yes, you are true sorry. I was thinking about if someone overrides _transfer and does add some extra controls without any revert only with returning 0. Code is perfect, thank you for describing kindly and for your contribution. Am 13.10.2018 um 11:24 schrieb Anton Bukov <[email protected]<mailto:[email protected]>>: @ardagokcek<https://github.com/ardagokcek> I think changing this lines order will not help in this case. You mean someone overrides _transfer? It should revert in case of failure. I used this order of lines because of order of lines 207-209. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#1370 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AGgZJsLBwyCQTolPXhyZbF8rrZMKy_1jks5ukbE_gaJpZM4XCOdq>.