Doubt about sending other native tokens to a contract like FundMe from lesson 4

[0xREALAldc]

Hi all,

I tried to search if anyone had done this question before and I didn't find anything, so if is a duplicate I would be happy if anyone could post the link to the question already done.

This being said, I was watching the lesson 4 and after Patrick said that in the fund method we could receive ETH or any native tokens from blockchains I was wondering what would happen if anyone instead of sending some ETH, sent some MATIC to my contract.

If I already had 1 ETH of balance in the contract, and someone send 5 MATIC, by what Patrick says in the course the transaction would go through with success and now the balance of my contract would have some ETH and MATIC as well.

I was wondering if when we call the withdraw method, it would withdraw both of the tokens?

Thanks in advance for anyone joining the discussion.

[alymurtazamemon]

@0xREALAldc Let me first clear the difference!

There are two types of currencies (You should search on ChatGPT or youtube for detailed differences).

1. Native coins (are the cryptocurrency of a blockchain which we use to perform operations on that blockchain such as we spend ethers on the Ethereum Blockchain, and Matic on the polygon blockchain).
2. ERC20 tokens (are the tokens created using smart contracts by following a standard).

We cannot send native coins to other blockchains, such as we cannot pay with Matic on the Ethereum Blockchain. But we can use one token on any other blockchain (it is the underlying thing first we convert the native coin to ERC20 representation and then send it as an ERC20 token to other blockchains).

I am not sure it makes sense to you right now but you just need to understand the difference between coin and token so search about it.

[0xREALAldc]

Hey Aly, thanks for your reply.

I understand the difference between the native token and a ERC20 token, I was just wondering while watching the lesson 4 about what it would happen if someone sent to the contract that we develop another token that isn't ETH....but now thinking more about it, and after your answer also, I realized that is impossible to someone send to our contract another token that isn't ETH right?

I was wondering about how a contract holds more than one token and how we can withdraw them from it, but I guess Patrick must teach us that in the DeFi lessons.

Thanks for your reply my friend, you helped me to think more about my question and understand better the concept of the contract that we developed.

[alymurtazamemon]

@0xREALAldc When you say contract holding tokens, here I want to guide that contracts only hold ether which is the native coin created to pay for gas purposes. All the other tokens you are talking about are just smart contracts which contain mappings and when you transfer tokens to some address the smart contract just updates those mappings.

i.e

mapping(address => uint256) public balances;

This is the balances mapping inside the ERC20 tokens so when you transfer the token to some address the smart contract just updates these mappings like this;

_balances[from] = fromBalance - amount;
_balances[to] += amount;

You will learn more about it later in ERC20 lesson.