SafeERC20 methods "safeApprove" & "safeTransfer"

[sasha]

Hi OZ team,

I am getting an error when using safeERC20, my smart contract is accepting USDC as payment to buy ERC1155 fractions, but every time I debug the code following the exact same steps from the threads below it is still throwing an error

SafeERC20, TokenTimelock, wrappers

Hey everyone, I was wondering: why are there wrapper contracts such as SafeERC20 and TokenTimelock? Why aren’t these children of another contract instead? Also… Does anyone have a working example of a SafeERC20? I just tried to create a wrapper of my token and integrate the unit tests of the ERC20, but even the most basic ERC20 function isn’t working anymore (TypeError: this.token.balanceOf is not a function) All I did was actually to take a SafeERC20Wrapper from SafeERC20Helpers (also I remov…

ERC20 transfer not working

When i tried to use the transfer() i get the error revert ERC20: transfer amount exceeds balance but when i use transferFrom() with little changes, i don’t get the error. What could be the issue, please? Attached is a screenshot to show both implementations. Using TransferFrom [Screen Shot 2020-01-07 at 9.46.44 AM] Using normal transfer [Screen Shot 2020-01-07 at 9.47.01 AM] Please, help!

transferFrom() always reverts with "revert ERC20: transfer amount exceeds allowance"

Environment Truffle, fresh project with an ERC20 constructor :memo:Details Hey, I’m trying to use the approve(), then transferFrom() methods from OpenZeppelin library, to transfer ERC20 from an account to another through my contract. approve() seems fine, allowance() returns the expected value, but after that transferFrom() with the same addresses reverts with transfer amount exceeds allowance. I approved the contract address to use tokens of account A, and transfer them to accou…

with safeApprove & safeTransfer error is "transfer exceeds allowance"
with safeIncreaseAllowance and safeTransferFrom error is "transfer exceeds balance"

I don't know what I am doing wrong, so your help will be greatly appreciated.

Note: I'm deploying on Polygon and using
USDC = IERC20(0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174);

Thank you in advance.

Environment

Remix IDE & Truffle

[frangio]

The way approve is used is that the user first needs to call approve on USDC, and then your contract is allowed to transferFrom. You can't call approve for the user because USDC's approve function has no way of knowing that you're authorized, except being called by the user themselves.

If you're specifically using USDC, you can look into permit as an alternative to approve.

[sasha]

Thank you so much Francisco for your response, I sincerely appreciate you answering this silly inquiry as I figured out my mistake after getting away from the code for 24H.

Thanks to you & OZ team for the continuous support & guidance.

[frangio]

Glad you figured out. Next time I encourage coming back to share the solution once you find it!

[sasha]

sure I will do it next time

Regards,