I write a simple smart contract to test the function approve() in the USDT, here are my code: pragma solidity ^0.4.25; contract EIP20Interface { uint256 public totalSupply; function balanceOf(address _owner) public view returns (uint256 balance); function transfer(address _to, uint2…

Hi @Skyge , USDT approve doesn’t comply with the ERC20 standard. I modified Test.sol to use SafeERC20 and this worked in Remix on a testnet (I haven’t tried on mainnet): Test.sol pragma solidity ^0.5.0; import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.4.0/contracts/token/ERC…

Does that mean I can call approve(spender, value) in the USDT contract directly, but I can not call the same function in a contract, cause it is not a standard ERC20 contract, but what is the reason for it?

Emmm, I know USDT is not compatible with ERC20 standard, so I am not check its returning value, I just call that function.

Hi @skyge , I deployed the Test.sol I created to mainnet and was able to use it to set an allowance on USDT. _owner: 0x101d4106751277cfe8b2181a194BaAe84916b250 _spender: 0x13ebd3443fa5575F0Eb173e323D8419F7452CfB1 I assume the issue is that the original Test called using the interface with a return…

That makes sense, thanks a lot!

Thanks for the clarification, it works on the mainnet, @Skyge @abcoathup just wondering is there any usdt asset address on testnet for testing purpose?

Hi, welcome! :wave: I do not think there is any USDT on the testnet from the acutal Tether, so if you wants to have a test on a testnet, you can use the source code on the mainnet to deploy a new one on the testnet to simulate.

@Skyge I’ve deployed the USDT contract to Ropsten testnet at 0xd5ffb36998e2e2df1402e33801a1949852055cb0, and I wrote some code to test how to deposit usdt into the smart contact and withdraw the deposited usdt. I’ve safeapprove the contract address at 0xd5ffb36998e2e2df1402e33801a1949852055cb0, but …

I think you should call the approve() out of this contract rather than use your function tokenAllowAll , so I think the correct steps should be: 1. usdt.approve(Test.address, amount); 2. deposit(asset, amount); Have I made myself clear?

Can not call the function approve() of the USDT contract

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Can not call the function approve() of the USDT contract

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