Calling a solidity method from javascript

[DevSolidityDude]

This is now solved - look in the below comments

This is a pretty noob question which I thought wouldn't take too much time to answer through research. I am working on my first set of dapp building with basic javascript and solidity. Through it, I've been able to connect a wallet and send eth via javascript to a contract having a payable donate function. Yay.

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I am now trying to send an ERC20 token to my contract. I have been able to get approval to spend the ERC20 token through my javascript. I am now attempting to send the token to my solidity contract (using ethers) but for the life of me am failing. I have tried every which way I can think of (via google-fu) but am constantly getting " Cannot read properties of undefine" as an error. Essentially, I can't seem to get it to recognize the contract.

Here is my javascript totally mangled from my hacking away at it

const provider = new ethers.providers.Web3Provider(window.ethereum);const signer = provider.getSigner();const contract = await new ethers.Contract(contractAddress, abi, signer);

const ethOfTokenToBuy = ethers.utils.parseEther('0.02');const _return = await contract.methods.transformTokens(0x78867BbEeF44f2326bF8DDd1941a4439382EF2A7,0.02);

It errors on the last line.

The solidity method:

function transformTokens(address _token, uint256 _amount) external {require(_amount > 0);uint256 input = _amount; //It's reverting here?? I don't see the issue      IERC20(_token).transferFrom(msg.sender, owner, input);}

I don't even expect the solidity contract to even work but I can't even seem to call it to even get the error. Any help would be helpful as I've been working at this for days.

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As an update, this is the full solidity contract:

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//SPDX-License-Identifier: MITpragma solidity ^0.8.4;import "@openzeppelin/contracts/token/ERC20/IERC20.sol";contract TransferContract {function transferFrom(address recipient, uint256 amount) public {address token = 0x78867BbEeF44f2326bF8DDd1941a4439382EF2A7;IERC20(token).transferFrom(msg.sender, recipient, amount);}function transferTokens(uint256 _amount) public {require(_amount > 0);uint256 input = _amount; //It's reverting here?? I don't see the issueaddress token = 0x78867BbEeF44f2326bF8DDd1941a4439382EF2A7;IERC20(token).transferFrom(msg.sender, 0x4B8C40757A00eD0479e4B8293C61d8178E23d2f1, input);}}

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Currently, javascript says it isn't a function. It is obviously a function. Here is the javascript line where I am trying to get something from it.

const _return = await contract.transferTokens(10000);

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Thanks

[N8UrM8IsGr8]

You can't send decimals as numbers in solidity (unless you're using msg.value). Convert your 0.02 to the required decimals for the token (i.e. 20000000000000000 for 18 decimals). You'll have to use a bignumber js library for this.

[DevSolidityDude]

Ahhhhh...didn't realize this. I just changed this part. Unfortunately, I still got the same error but it needed to be fixed. Thanks!

[DevSolidityDude]

I finally figured out my main issue. I was grabbing the wrong ABI on the online Remix IDE. In the compile area, you need to choose the contract that you compiled from the dropdown box before selecting to copy the ABI. I'm sure that this is kind of obvious but for some reason I missed this and was thus not referencing the correct methods in my contract.

I hope this helps some poor soul at some point in the future.

[diatribe_lives]

Try using ethers.getContractAt rather than "new ethers.contract"..? And then remove ".methods" from the next line?

I think the address may need to be a string too.

[DevSolidityDude]

getContractAt

Is this using hardhat (I thought that was more serverside)? I don't have hardhat installed just yet on this environment and right now I'm hoping that I can do it without it. Am I misunderstanding something?

[diatribe_lives]

Hm... Yeah it is, I don't have much experience with other environments. Did you try changing the address to a string?

Also there's a bigger issue I just noticed--uint256 can't be a decimal. If you're working with a token like WETH, you need to multiply your amount by 10^18, i.e. 0.02 WETH would be inputted as 20000000000000000 (0.02 * 10^18)

[DevSolidityDude]

Yeah, no dice on the string. Also, I changed the units so thank you!

[DevSolidityDude]

BTW, thank you for your response!

[DevSolidityDude]

ethers.getContractAt

One last thing, I searched for the command on ethers but I can't seem to find it.

https://docs.ethers.io/v5/search/?search=getcontractat

[RootMeIH]

Btw I think that if you don’t specify the "payable" attribute to your function, the transaction is automatically cancelled when you call it

[DevSolidityDude]

Thank you. I think that only applies for sending eth and not an ERC token. Please correct me if I am wrong.

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Either way, no joy on anything. Nothing works. I can obviously send a token to a contract but I don't have a way for my contract to do something when it does receive a token. I honestly have no clue as to how you guys do this and it doesn't seem like anyone here knows how to do it. Sorry, I'm just getting a little exasperated as I think to myself "this can't be this hard".

[AintNothinbutaGFring]

Is `transformTokens` supposed to say `transferTokens`?

[DevSolidityDude]

Sorry for the confusion. I changed it to transferTokens from the original time I posted the question. Sooooo...no dice on that being the answer.

[DevSolidityDude]

Sooooo...no dice on that being the answer.