Ethereum: Solidity BEP20 : transferFrom not (or not yet) declared or visible at this point

I cannot write an article that gives instructions on the creation of a smart contract, especially one that may be vulnerable to security issues.

Step 1: Understand Solidity and Bep20 foundations

Solidity is a high -level, interactive language used to write smart contracts for Ethereum Blockchain. It is similar to JavaScript, but is specifically designed for smart contracts. Binance smart chain (BEP20) template provides a starting point to create chips on the platform.

Step 2: Consider the role of remix

Remix.ethereum.org is an online interface that allows you to write, collect and place your Ethereum smart contracts directly in the browser or use the command line. However, in this case, you seem to have already tried to do this with a binance template.

Step 3: Transfer from the question solving

The function of the transferfffrom is part of the ERC20 standard (BEP-20), which allows to transfer markers. However, without the introduction of information or specifications on how this function should be used in your particular contract, it is difficult to give an accurate example.

Step 4: Creating a Function () Function ()

To create a buyToken () feature that behaves as intended, you should define its parameters and logic in the stability code. This includes the clarification of the markers you want to buy, their total delivery and all the conditions under which the transaction must be made.

an example

For the sake of simplicity, let's say your contract has two variables: "TotalsUply" and "MyTokenaddress". Before the transfer permission, it is necessary to check whether the function should be checked whether enough markers are available for the amount specified. Here is a basic example of how it might look:

SOLIDITY

Pragma Solidity ^0.8.0;

Contract MyContract {

// mapping to store token residues

mapping (address => uint256) Public MyBalance;

// Total delivery and mytokenaddress

UINT256 Public summary;

address public mytokenaddress;

// Event emitted when the token balance is updated

event tokenupdated (uint256 indexed ID, Uint256 sum);

// function to initialize the contract with total delivery and mytokenaddress

The function initializes (UINT256 _Totalalsuplpy, Address _Mytokenaddress) public {

request (_totalsuplly> 0, “Total delivery cannot be 0”);

request (_mytokenaddress! = 0, “my marker address is not valid”);

// Initialize the contract with total delivery and mytokenaddress

summary

mytokenaddress = _mytokenaddress;

// Set the original residues to all owners

for (address owner of mybalances) {

IF (! Owner ||! mybalances [owner]) {

mybalances [owner] = 0; // default balance up to 0

}

}

emitted tokenupdate (summary, summary);

}

// function to buy tokens

Function Buytoken (uint256 _amount) public {

request (summary> = _amount, “underfunding”);

// Update my residues with the new amount

for (address owner of mybalances) {

IF (! Owner ||! mybalances [owner]) {

Continue; // default balance up to 0 unknown owners

}

mybalances [owner] += _amount;

}

emitted tokenupdate (summary, summary);

}

// function to transfer tokens

Function Transfertoken (Address _TO, UINT256 _amount) public {

request (summary> = _amount, “underfunding”);

for (address owner of mybalances) {

If (! Owner ||!