Hi all 
I'm relatively new in Solidity and trying to create a BEP20 smart contract and run in testnet to get a glimpse of how the whole environment works.
Lot of questions and issue faced by me:
-IUniswap & reflective.finance code works in BEP20 contract?
-To create BNB Smart Contract, should use IBEP20 or IECR20 in the code
contract Trial is Context, IBEP20, Ownable {
using SafeMath for uint256;
using Address for address;
mapping (address => uint256) private _balances;
mapping (address => mapping (address => uint256)) private _allowances;
mapping (address => bool) private _isExcludedFromFee;
mapping (address => bool) private _isExcluded;
address[] private _excluded
uint256 private constant MAX = ~uint256(0);
uint256 private _tTotal = 1000000 * 10**6 * 10**18;
uint256 private _rTotal = (MAX - (MAX % _tTotal));
uint256 private _tFeeTotal;
uint256 private _totalSupply;
uint8 private _decimals;
string private _symbol;
string private _name;
uint256 public _liquidityFee = 4;
uint256 private _previousLiquidityFee = _liquidityFee;
uint256 public _reflectionFee = 4;
uint256 private _previousReflectionFee = _reflectionFee;
uint256 public _devFee = 2;
uint256 private _previousDevFee = _devFee;
uint256 public _maxTxAmount = 5000000 * 10**6 * 10**9;
uint256 private numTokensSellToAddToLiquidity = 500000 * 10**6 * 10**9;
constructor() public {
_name = "NAME";
_symbol = "TOKENSYMBOL";
_decimals = 18;
_totalSupply = 1000000000000; //1 trillion
_balances[msg.sender] = _totalSupply;
emit Transfer(address(0), msg.sender, _totalSupply);
}
/**
* @dev Returns the bep token owner.
*/
function getOwner() external view returns (address) {
return owner();
}
/**
* @dev Returns the token decimals.
*/
function decimals() external view returns (uint8) {
return _decimals;
}
/**
* @dev Returns the token symbol.
*/
function symbol() external view returns (string memory) {
return _symbol;
}
/**
* @dev Returns the token name.
*/
function name() external view returns (string memory) {
return _name;
}
/**
* @dev See {BEP20-totalSupply}.
*/
function totalSupply() external view returns (uint256) {
return _totalSupply;
}
/**
* @dev See {BEP20-balanceOf}.
*/
function balanceOf(address account) external view returns (uint256) {
return _balances[account];
}
/**
* @dev See {BEP20-transfer}.
*
* Requirements:
*
* - `recipient` cannot be the zero address.
* - the caller must have a balance of at least `amount`.
*/
function transfer(address recipient, uint256 amount) external returns (bool) {
_transfer(_msgSender(), recipient, amount);
return true;
}
/**
* @dev See {BEP20-allowance}.
*/
function allowance(address owner, address spender) external view returns (uint256) {
return _allowances[owner][spender];
}
/**
* @dev See {BEP20-approve}.
*
* Requirements:
*
* - `spender` cannot be the zero address.
*/
function approve(address spender, uint256 amount) external returns (bool) {
_approve(_msgSender(), spender, amount);
return true;
}
/**
* @dev See {BEP20-transferFrom}.
*
* Emits an {Approval} event indicating the updated allowance. This is not
* required by the EIP. See the note at the beginning of {BEP20};
*
* Requirements:
* - `sender` and `recipient` cannot be the zero address.
* - `sender` must have a balance of at least `amount`.
* - the caller must have allowance for `sender`'s tokens of at least
* `amount`.
*/
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool) {
_transfer(sender, recipient, amount);
_approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "BEP20: transfer amount exceeds allowance"));
return true;
}
/**
* @dev Atomically increases the allowance granted to `spender` by the caller.
*
* This is an alternative to {approve} that can be used as a mitigation for
* problems described in {BEP20-approve}.
*
* Emits an {Approval} event indicating the updated allowance.
*
* Requirements:
*
* - `spender` cannot be the zero address.
*/
function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
return true;
}
/**
* @dev Atomically decreases the allowance granted to `spender` by the caller.
*
* This is an alternative to {approve} that can be used as a mitigation for
* problems described in {BEP20-approve}.
*
* Emits an {Approval} event indicating the updated allowance.
*
* Requirements:
*
* - `spender` cannot be the zero address.
* - `spender` must have allowance for the caller of at least
* `subtractedValue`.
*/
function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "BEP20: decreased allowance below zero"));
return true;
}
/**
* @dev Creates `amount` tokens and assigns them to `msg.sender`, increasing
* the total supply.
*
* Requirements
*
* - `msg.sender` must be the token owner
*/
function mint(uint256 amount) public onlyOwner returns (bool) {
_mint(_msgSender(), amount);
return true;
}
function totalFees() public view returns (uint256) {
return _tFeeTotal;
}
function deliver(uint256 tAmount) public {
address sender = _msgSender();
require(!_isExcluded[sender], "Excluded addresses cannot call this function");
(uint256 rAmount,,,,,) = _getValues(tAmount);
_rOwned[sender] = _rOwned[sender].sub(rAmount);
_rTotal = _rTotal.sub(rAmount);
_tFeeTotal = _tFeeTotal.add(tAmount);
}
function reflectionFromToken(uint256 tAmount, bool deductTransferFee) public view returns(uint256) {
require(tAmount <= _tTotal, "Amount must be less than supply");
if (!deductTransferFee) {
(uint256 rAmount,,,,,) = _getValues(tAmount);
return rAmount;
} else {
(,uint256 rTransferAmount,,,,) = _getValues(tAmount);
return rTransferAmount;
}
}
function tokenFromReflection(uint256 rAmount) public view returns(uint256) {
require(rAmount <= _rTotal, "Amount must be less than total reflections");
uint256 currentRate = _getRate();
return rAmount.div(currentRate);
}
/**
* @dev Moves tokens `amount` from `sender` to `recipient`.
*
* This is internal function is equivalent to {transfer}, and can be used to
* e.g. implement automatic token fees, slashing mechanisms, etc.
*
* Emits a {Transfer} event.
*
* Requirements:
*
* - `sender` cannot be the zero address.
* - `recipient` cannot be the zero address.
* - `sender` must have a balance of at least `amount`.
*/
function _transfer(address sender, address recipient, uint256 amount) private {
require(sender != address(0), "ERC20: transfer from the zero address");
require(recipient != address(0), "ERC20: transfer to the zero address");
require(amount > 0, "Transfer amount must be greater than zero");
if(sender != owner() && recipient != owner())
require(amount <= _maxTxAmount, "Transfer amount exceeds the maxTxAmount.");
/*
// is the token balance of this contract address over the min number of
// tokens that we need to initiate a swap + liquidity lock?
// also, don't get caught in a circular liquidity event.
// also, don't swap & liquify if sender is uniswap pair.
uint256 contractTokenBalance = balanceOf(address(this));
if(contractTokenBalance >= _maxTxAmount)
{
contractTokenBalance = _maxTxAmount;
}
bool overMinTokenBalance = contractTokenBalance >= numTokensSellToAddToLiquidity;
if (
overMinTokenBalance &&
!inSwapAndLiquify &&
sender != uniswapV2Pair &&
swapAndLiquifyEnabled
) {
contractTokenBalance = numTokensSellToAddToLiquidity;
//add liquidity
swapAndLiquify(contractTokenBalance);
}
//indicates if fee should be deducted from transfer
bool takeFee = true;
//if any account belongs to _isExcludedFromFee account then remove the fee
if(_isExcludedFromFee[sender] || _isExcludedFromFee[recipient]){
takeFee = false;
}
//transfer amount, it will take tax, burn, liquidity fee
_tokenTransfer(sender,recipient,amount,takeFee);
*/
}
/** @dev Creates `amount` tokens and assigns them to `account`, increasing
* the total supply.
*
* Emits a {Transfer} event with `from` set to the zero address.
*
* Requirements
*
* - `to` cannot be the zero address.
*/
function _mint(address account, uint256 amount) internal {
require(account != address(0), "BEP20: mint to the zero address");
_totalSupply = _totalSupply.add(amount);
_balances[account] = _balances[account].add(amount);
emit Transfer(address(0), account, amount);
}
/**
* @dev Destroys `amount` tokens from `account`, reducing the
* total supply.
*
* Emits a {Transfer} event with `to` set to the zero address.
*
* Requirements
*
* - `account` cannot be the zero address.
* - `account` must have at least `amount` tokens.
*/
function _burn(address account, uint256 amount) internal {
require(account != address(0), "BEP20: burn from the zero address");
_balances[account] = _balances[account].sub(amount, "BEP20: burn amount exceeds balance");
_totalSupply = _totalSupply.sub(amount);
emit Transfer(account, address(0), amount);
}
/**
* @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
*
* This is internal function is equivalent to `approve`, and can be used to
* e.g. set automatic allowances for certain subsystems, etc.
*
* Emits an {Approval} event.
*
* Requirements:
*
* - `owner` cannot be the zero address.
* - `spender` cannot be the zero address.
*/
function _approve(address owner, address spender, uint256 amount) internal {
require(owner != address(0), "BEP20: approve from the zero address");
require(spender != address(0), "BEP20: approve to the zero address");
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
}
/**
* @dev Destroys `amount` tokens from `account`.`amount` is then deducted
* from the caller's allowance.
*
* See {_burn} and {_approve}.
*/
function _burnFrom(address account, uint256 amount) internal {
_burn(account, amount);
_approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "BEP20: burn amount exceeds allowance"));
}
function excludeFromFee(address account) public onlyOwner {
_isExcludedFromFee[account] = true;
}
function includeInFee(address account) public onlyOwner {
_isExcludedFromFee[account] = false;
}
function setLiquidityFeePercent(uint256 liquidityFee) external onlyOwner() {
_liquidityFee = liquidityFee;
}
function setReflectionFeePercent(uint256 reflectionFee) external onlyOwner() {
_reflectionFee = reflectionFee;
}
function setDevFeePercent(uint256 devFee) external onlyOwner() {
_devFee = devFee;
}
function setMaxTxPercent(uint256 maxTxPercent) external onlyOwner() {
_maxTxAmount = _totalSupply.mul(maxTxPercent).div(
10**2
);
}
function _reflectFee(uint256 rFee, uint256 tFee) private {
_rTotal = _rTotal.sub(rFee);
_tFeeTotal = _tFeeTotal.add(tFee);
}
function calculateLiquidityFee(uint256 _amount) private view returns (uint256) {
return _amount.mul(_liquidityFee).div(
10**2
);
}
function calculateRefelctionFee(uint256 _amount) private view returns (uint256) {
return _amount.mul(_reflectionFee).div(
10**2
);
}
function calculateDevFee(uint256 _amount) private view returns (uint256) {
return _amount.mul(_devFee).div(
10**2
);
}
function removeAllFee() private {
if(_liquidityFee == 0 && _reflectionFee == 0 && _devFee == 0) return;
_previousLiquidityFee = _liquidityFee;
_previousReflectionFee = _reflectionFee;
_previousDevFee = _devFee;
_liquidityFee = 0;
_reflectionFee = 0;
_devFee = 0;
}
function restoreAllFee() private {
_liquidityFee = _previousLiquidityFee;
_reflectionFee = _previousReflectionFee;
_devFee = _previousDevFee;
}
function isExcludedFromFee(address account) public view returns(bool) {
return _isExcludedFromFee[account];
}
//this method is responsible for taking all fee, if takeFee is true
function _tokenTransfer(address sender, address recipient, uint256 amount,bool takeFee) private {
if(!takeFee)
removeAllFee();
if (_isExcluded[sender] && !_isExcluded[recipient]) {
_transferFromExcluded(sender, recipient, amount);
} else if (!_isExcluded[sender] && _isExcluded[recipient]) {
_transferToExcluded(sender, recipient, amount);
} else if (!_isExcluded[sender] && !_isExcluded[recipient]) {
_transferStandard(sender, recipient, amount);
} else if (_isExcluded[sender] && _isExcluded[recipient]) {
_transferBothExcluded(sender, recipient, amount);
} else {
_transferStandard(sender, recipient, amount);
}
if(!takeFee)
restoreAllFee();
}
function _transferBothExcluded(address sender, address recipient, uint256 tAmount) private {
(uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getValues(tAmount);
_tOwned[sender] = _tOwned[sender].sub(tAmount);
_rOwned[sender] = _rOwned[sender].sub(rAmount);
_tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
_rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
_takeLiquidity(tLiquidity);
_reflectFee(rFee, tFee);
emit Transfer(sender, recipient, tTransferAmount);
}
function _transferStandard(address sender, address recipient, uint256 tAmount) private {
(uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getValues(tAmount);
_rOwned[sender] = _rOwned[sender].sub(rAmount);
_rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
_takeLiquidity(tLiquidity);
_reflectFee(rFee, tFee);
emit Transfer(sender, recipient, tTransferAmount);
}
function _transferToExcluded(address sender, address recipient, uint256 tAmount) private {
(uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getValues(tAmount);
_rOwned[sender] = _rOwned[sender].sub(rAmount);
_tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
_rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
_takeLiquidity(tLiquidity);
_reflectFee(rFee, tFee);
emit Transfer(sender, recipient, tTransferAmount);
}
function _transferFromExcluded(address sender, address recipient, uint256 tAmount) private {
(uint256 rAmount, uint256 rTransferAmount, uint256 rFee, uint256 tTransferAmount, uint256 tFee, uint256 tLiquidity) = _getValues(tAmount);
_tOwned[sender] = _tOwned[sender].sub(tAmount);
_rOwned[sender] = _rOwned[sender].sub(rAmount);
_rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
_takeLiquidity(tLiquidity);
_reflectFee(rFee, tFee);
emit Transfer(sender, recipient, tTransferAmount);
}
}
May I know what caused the error?
I'm still trial and error on this smart contact.
Thank you in advance and hope for an answer!
