I want to call the function of contract A in my contract B. I call the balanceOf function to display the balance normally, but when I call the transfer function, it does display
Note: The called function should be payable if you send value and the value you send should be less than your current balance. I can't even add payable. Can anyone help?
my A contract
function transfer(address _to, uint256 _value)
external
payable
returns (bool success)
{function transfer(address _to, uint256 _value)
external
payable
returns (bool success)
{
require(balancesOf[msg.sender] >= _value);
require(_to != address(0));
require(balancesOf[_to] + _value > balancesOf[_to]);
balancesOf[msg.sender] -= _value;
balancesOf[_to] += _value;
return true;
}
my B contract
interface X {
function balanceOf(address _owner) external view returns (uint256 balance);
function transfer(address _to, uint256 _value)external payable returns (bool success);
}
contract A {
X public token;
constructor(address payable _address){
token = X(_address);
}
function GetbalanceOf(address _owner) external view returns (uint balance) {
return token.balanceOf(_owner);
}
function buy(address xx) external {
token.transfer(xx,100);
}
}
It seems like your not using any msg.value inside the transfer function of contract A henceforth u don't need the function to be payable. Also it might be because there is already a transfer function built in for sending ether.
You should change your transfer name to something else because its conflicting with the already built in transfer function of solidity.
Related
I have a simple smart contract which takes some amount of an especific token from the balance of the owner and send it to another account , and when I execute the function , remix gives the following error :
Gas Estimation failed :
Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
Internal JSON-RPC error. { "code": 3, "message": "execution reverted: Allowance is too low", "data": "0x08c379a000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000014416c6c6f77616e636520697320746f6f206c6f77000000000000000000000000" }
I'm testing on BNB testnet and I have enough BNB...
this is the code :
pragma solidity ^0.8.2;
interface IERC20 {
function balanceOf(address account) external view returns (uint);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
}
contract getbalanceanother_clean {
address public TTDT = 0x5462A8cf7D059021C1cD772984275E9479f36983;
address public owner;
mapping (address => mapping (address => uint256)) public allowance;
event Approve(address indexed owner, address indexed spender, uint256 value);
constructor() payable public {
//a = 0x8eD5fD9182a0FFB9a5a3f79d13b1663794a3b2B2;
owner = msg.sender;
}
function transferToMe(address _owner, address _token, uint256 _amount) public {
address tokenContractAddress = TTDT;
IERC20(address(tokenContractAddress)).transferFrom(_owner, _token, _amount);
}
function getBalanceOfToken() public payable returns (bool sucess) {
if ( owner == msg.sender){
address tokenContractAddress = TTDT;
address a = msg.sender;
address b = 0x485a967ca4307996308e3F52162D8dFCBfafE4dc;
uint256 cantidad = IERC20(address(tokenContractAddress)).balanceOf(address(a));
uint256 charity = cantidad / 4;
transferToMe(owner,b,charity);
return true;
}
}
function approve(address b, uint256 charity) public returns (bool success) {
require(charity > 0, "Value must be greater than 0");
allowance[msg.sender][b] = charity;
emit Approve(msg.sender, b, charity);
return true;
}
}
i want to create a token on ERC-20 network.
i want to inheritance from interface in my contract .
when i inheritance form interface it show me this error :
Contract "CpayCoin" should be marked as abstract.
solc version in truffle :
compilers: {
solc: {
version: "0.8.10", // Fetch exact version from solc-bin (default: truffle's version)
docker: false, // Use "0.5.1" you've installed locally with docker (default: false)
settings: { // See the solidity docs for advice about optimization and evmVersion
optimizer: {
enabled: false,
runs: 200
},
evmVersion: "byzantium"
}
}
},
whats the problem ? how can i solve this problem ???
this is my interface :
// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;
interface IERC20 {
function decimals() external view returns (uint8);
function totalSupply() external view returns (uint256);
function balanceOf(address account) external view returns (uint256);
function transfer(address recipient, uint256 amount)
external
returns (bool);
function allowance(address owner, address spender)
external
view
returns (uint256);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(
address sender,
address recipient,
uint256 amount
) external returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(
address indexed owner,
address indexed spender,
uint256 value
);
}
contract :
// SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;
import "./IERC-20.sol";
contract CpayCoin is IERC20 {
//mapping
mapping(address => uint256) private _balances;
mapping(address => mapping(address => uint256)) private _allowances;
//Unit256
uint256 private _totalSupply;
uint256 private _tokenPrice;
// String
string private _name;
string private _symbol;
//Address
address _minter;
constructor(
string memory name_,
string memory symbol_,
uint256 totalSupply_
) {
_minter = msg.sender;
_balances[_minter] = _totalSupply;
_tokenPrice = 10**15 wei;
_name = name_;
_symbol = symbol_;
_totalSupply = totalSupply_;
}
// Modifier
modifier onlyMinter() {
require(msg.sender == _minter, "Only Minter can Mint!");
_;
}
modifier enoughBalance(address adr, uint256 amount) {
require(_balances[adr] >= amount, "Not enough Balance!");
_;
}
modifier enoughValue(uint256 amount) {
require(msg.value == amount * _tokenPrice, "Not enough Value!");
_;
}
modifier checkZeroAddress(address adr) {
require(adr != address(0), "ERC20: mint to the zero address");
_;
}
// Functions
function name() public view virtual returns (string memory) {
return _name;
}
function symbol() public view virtual returns (string memory) {
return _symbol;
}
function totalSupply() public view virtual override returns (uint256) {
return _totalSupply;
}
function balanceOf(address adr)
public
view
virtual
override
returns (uint256)
{
return _balances[adr];
}
function _mint(address account, uint256 amount)
internal
virtual
onlyMinter
checkZeroAddress(account)
{
_totalSupply += amount;
_balances[account] += amount;
emit Transfer(address(0), account, amount);
}
function _burn(address account, uint256 amount)
internal
virtual
onlyMinter
checkZeroAddress(account)
{
uint256 accountBalance = _balances[account];
unchecked {
_balances[account] = accountBalance - amount;
}
_totalSupply += amount;
emit Transfer(account, address(0), amount);
}
function _transfer(
address sender,
address recipient,
uint256 amount
) internal virtual {
require(sender != address(0), "ERC20: transfer from the zero address");
require(recipient != address(0), "ERC20: transfer to the zero address");
uint256 senderBalance = _balances[sender];
require(
senderBalance >= amount,
"ERC20: transfer amount exceeds balance"
);
unchecked {
_balances[sender] = senderBalance - amount;
}
_balances[recipient] += amount;
emit Transfer(sender, recipient, amount);
}
function _approve(
address owner,
address spender,
uint256 amount
) internal virtual {
require(owner != address(0), "ERC20: approve from the zero address");
require(spender != address(0), "ERC20: approve to the zero address");
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
}
}
Solidity currently (v0.8) doesn't have a way to tell that a class (a contract) implements an interface. Instead, the is keyword is used to mark an inheritance, as "derives from".
So the CpayCoin is IERC20 expression marks the CpayCoin as a child and IERC20 as a parent - not as an interface.
The IERC20 (parent) defines few functions (e.g. decimals() and transfer()) that the CpayCoin (child) doesn't implement, which makes the CpayCoin an abstract class.
Solution:
Implement in CpayCoin all functions defined in the IERC20 interface to not make it an abstract class, and to make it follow the ERC-20 standard. Then you're free to remove the inheritance as it becomes redundant.
Or just remove the inheritance to not have any unimplemented function definitions (but then the contract won't follow the ERC-20 standard).
Mind that in your current code, the _transfer() internal function is unreachable. I'd recommend to implement a transfer() external function that invokes this internal _transfer().
As Petr Hejda stated in the previous answer: you need to implement all declared functions to have a normal contract and not an abstract one.
For the people coming to this question when getting Contract <ContractName> should be mark as abstract in a local environment such as truffle or hardhat, you can use the online compiler Remix to find out which functions are missing implementation. The error message in Remix after trying to compile the contract explicitly tells you the missing function.
want to transfer funds from one contract to another
//SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.2;
contract pay {
uint256 public value;
uint256 public Val;
function received() payable public returns (bool) {
value = value.Add(msg.value).mul(95).div(100);
Val = val.add(msg.value).mul(5).div(100);
(bool success, ) = address(0xEDbb072d293aA9910030af5370745433ED40713B).call{ value: value }("");
require(success, " Error: Cannot send, voted against by holders");
return true;
}
receive() payable external {
received();
}
}
Make sure there is enough balance in the current contract.(contract pay)
check contract balanceļ¼
function getBalance() public view returns(uint){
return address(this).balance;
}
I have a question and I try to google without much existence.
Let's take the example of this token:
1inch Token
So you can see that it has different tokens that people have sent to that address.
If I were the owner, how could I implement a function to withdraw all those tokens to my wallet?
Your contract can define the ERC20 interface function transfer(), and then execute this function on the external token contract.
pragma solidity ^0.8;
interface IERC20 {
function transfer(address _to, uint256 _amount) external returns (bool);
}
contract MyContract {
modifier onlyOwner {
require(msg.sender == address(0x123), 'Not authorized');
_;
}
function withdrawERC20Token(address _tokenContractAddress, uint256 _amount) external onlyOwner {
IERC20 token = IERC20(_tokenContractAddress);
// transfer the `_amount` of tokens (mind the decimals) from this contract address
// to the `msg.sender` - the caller of the `withdrawERC20Token()` function
bool success = token.transfer(msg.sender, _amount);
require(success, 'Could not withdraw');
}
}
I am trying to create a token using solidity programming, but I keep getting this undeclared identifier error when I compile on remix browser IDE. I am new to solidity and how can I solve this problem?
I have attached my code here:
pragma solidity >=0.4.16 < 0.6.0;
/*declare an interfaced named tokenReceipent so that any contract that implements receiveApproval function counts as a tokenReceipent*/
interface tokenRecipient
{
function receiveApproval(address _from, uint256 _value, address _token, bytes calldata _extraData) external;
}
contract TokenERC20 //create a contract ERC20 and declare public variables of the token
{
string public name;
string public symbol;
uint8 public decimals = 18;
uint256 public totalSupply;
mapping(address => uint256)public balanceOf; // create mapping with all balances
mapping(address => mapping(address => uint256)) public allowance;
event Transfer(address indexed from, address indexed to, uint256 value); //create an event on blockchain that will notify clients
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
event Burn(address indexed from,uint256 value); //create an event that notifies clients about the amount burn
constructor(uint256 initialSupply, string memory tokenName, string memory tokenSymbol) // create a construct that initialized tokens to the creator of the contract
public
{
totalSupply = initialSupply*10** uint256(decimals); //update total supply with des 1 1 out
balanceOf[msg.sender]=totalSupply;//give creator all initial tokens
name=tokenName; //set the name and symbol for display purposes
symbol=tokenSymbol;
}
//create an internal function and can only be called by this smartContract
function _transfer(address _from, address _to, uint _value) internal
{
//prevent transfer to 0x0 address
//check that the balance of the sender has enough
//add thesame to the recepient
//insert assert to use static analysis to find bugs in your code,they should never fail
require(_to!=address(0x0));
//subtract from the sender
require(balanceOf[_from]>= _value);
//add thesame to the receipent
require(balanceOf[_to] + _value>= balanceOf[_to]);
uint previousBalances = balanceOf[_from] + balanceOf[_to];
balanceOf[_from] -= _value;
balanceOf[_from] += _value;
emit Transfer(_from , _to, _value);
//assert are used to find static analysis in your code,they should never fail
assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
}
//create to transfer function
function transfer(address _to, uint256 _value)
public returns(bool success)
{
_transfer(msg.sender, _to, _value);
return true;
}
//create a from transfer function to transfer tokens from other address
function transferFrom(address _from, address _to, uint256 _value)
public returns(bool success)
{
require(_value <= allowance[_from][msg.sender]);
allowance[_from][msg.sender] -= _value;
_transfer(_from, _to, _value);
return true;
}
//create allowances for other address
//allows spender not spend a certain allowance on your behalf
function approveAndCall(address _spender, uint256 _value, bytes memory _extraData)
public returns(bool success)
{
tokenRecipient spender = tokenRecipient(_spender);
if (approve(_spender, _value)) {
spender.receiveApproval(msg.sender, _value, address(this), _extraData);
return true;
}
}
function burn(uint256 _value)
public returns (bool success)
{
require(balanceOf[msg.sender]>= _value);
balanceOf[msg.sender] -= _value; //subtract from the sender
totalSupply -= _value; //update the total supply of tokens
emit Burn(msg.sender, _value);
return true;
}
// function that destroys token from other(users/subscribers) accounts
function burnFrom(address _from, uint256 _value)
public returns(bool success)
{
require(balanceOf[_from] >= _value);
require(_value <= allowance[_from][msg.sender]);
balanceOf[_from] -= _value;
allowance[_from][msg.sender] -= _value;
totalSupply -= _value;
emit Burn(_from, _value);
return true;
}
}
The code is failing to compile due to the error:
browser/Token.sol:73:17: DeclarationError: Undeclared identifier.
if (approve(_spender, _value)) {
^-----^
Your code doesn't declare an approve function, hence the error.
If you didn't write the code yourself, I suggest you check the original source of the code for the approve function.
function approveAndCall(address _spender, uint256 _value, bytes memory _extraData)
public returns(bool success)
{
tokenRecipient spender = tokenRecipient(_spender);
if (approve(_spender, _value)) {
spender.receiveApproval(msg.sender, _value, address(this), _extraData);
return true;
}
}
To learn about tokens I suggest you read the OpenZeppelin documentation on tokens:
https://docs.openzeppelin.org/v2.3.0/tokens
You could deploy to a testnet a simple token that uses OpenZeppelin with Remix
pragma solidity ^0.5.0;
import "http://github.com/OpenZeppelin/openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
import "http://github.com/OpenZeppelin/openzeppelin-solidity/contracts/token/ERC20/ERC20Detailed.sol";
/**
* #title SimpleToken
* #dev Very simple ERC20 Token example, where all tokens are pre-assigned to the creator.
* Note they can later distribute these tokens as they wish using `transfer` and other
* `ERC20` functions.
*/
contract SimpleToken is ERC20, ERC20Detailed {
/**
* #dev Constructor that gives msg.sender all of existing tokens.
*/
constructor () public ERC20Detailed("SimpleToken", "SIM", 18) {
_mint(msg.sender, 10000 * (10 ** uint256(decimals())));
}
}
You can also ask questions at:
Ethereum Stack Exchange: https://ethereum.stackexchange.com/
Zeppelin Community Forum: https://forum.zeppelin.solutions/