solidity智能合约如何实现跨合约调用函数

背景

比如现在有一个需求、我需要通过外部合约获取BRC20 token的总交易量。那么我需要在brc20的转账函数里面做一些调整，主要是两个函数内统计转移量。然后再提供外部获取函数。

  /*** @dev Sets `amount` as the allowance of `spender` over the caller's tokens.** Returns a boolean value indicating whether the operation succeeded.** IMPORTANT: Beware that changing an allowance with this method brings the risk* that someone may use both the old and the new allowance by unfortunate* transaction ordering. One possible solution to mitigate this race* condition is to first reduce the spender's allowance to 0 and set the* desired value afterwards:* https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729** Emits an {Approval} event.*/function approve(address spender, uint256 amount) external returns (bool);/*** @dev Moves `amount` tokens from `sender` to `recipient` using the* allowance mechanism. `amount` is then deducted from the caller's* allowance.** Returns a boolean value indicating whether the operation succeeded.** Emits a {Transfer} event.*/function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

实操

1、定义了一个函数接口

 // SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;interface Iquery{function getTotalTransferAmount() external  view returns (uint256);
}

2、BRC20 token实现目标函数

// SPDX-License-Identifier: MIT
pragma solidity >0.4.0 <= 0.9.0;interface IBEP20 {/*** @dev Returns the amount of tokens in existence.*/function totalSupply() external view returns (uint256);/*** @dev Returns the token decimals.*/function decimals() external view returns (uint8);/*** @dev Returns the token symbol.*/function symbol() external view returns (string memory);/*** @dev Returns the token name.*/function name() external view returns (string memory);/*** @dev Returns the bep token owner.*/function getOwner() external view returns (address);/*** @dev Returns the amount of tokens owned by `account`.*/function balanceOf(address account) external view returns (uint256);/*** @dev Moves `amount` tokens from the caller's account to `recipient`.** Returns a boolean value indicating whether the operation succeeded.** Emits a {Transfer} event.*/function transfer(address recipient, uint256 amount) external returns (bool);/*** @dev Returns the remaining number of tokens that `spender` will be* allowed to spend on behalf of `owner` through {transferFrom}. This is* zero by default.** This value changes when {approve} or {transferFrom} are called.*/function allowance(address _owner, address spender) external view returns (uint256);/*** @dev Sets `amount` as the allowance of `spender` over the caller's tokens.** Returns a boolean value indicating whether the operation succeeded.** IMPORTANT: Beware that changing an allowance with this method brings the risk* that someone may use both the old and the new allowance by unfortunate* transaction ordering. One possible solution to mitigate this race* condition is to first reduce the spender's allowance to 0 and set the* desired value afterwards:* https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729** Emits an {Approval} event.*/function approve(address spender, uint256 amount) external returns (bool);/*** @dev Moves `amount` tokens from `sender` to `recipient` using the* allowance mechanism. `amount` is then deducted from the caller's* allowance.** Returns a boolean value indicating whether the operation succeeded.** Emits a {Transfer} event.*/function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);/*** @dev Emitted when `value` tokens are moved from one account (`from`) to* another (`to`).** Note that `value` may be zero.*/event Transfer(address indexed from, address indexed to, uint256 value);/*** @dev Emitted when the allowance of a `spender` for an `owner` is set by* a call to {approve}. `value` is the new allowance.*/event Approval(address indexed owner, address indexed spender, uint256 value);
}/** @dev Provides information about the current execution context, including the* sender of the transaction and its data. While these are generally available* via msg.sender and msg.data, they should not be accessed in such a direct* manner, since when dealing with GSN meta-transactions the account sending and* paying for execution may not be the actual sender (as far as an application* is concerned).** This contract is only required for intermediate, library-like contracts.*/
contract Context {// Empty internal constructor, to prevent people from mistakenly deploying// an instance of this contract, which should be used via inheritance.constructor () { }function _msgSender() internal view returns (address) {return msg.sender;}function _msgData() internal view returns (bytes memory) {this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691return msg.data;}
}/*** @dev Wrappers over Solidity's arithmetic operations with added overflow* checks.** Arithmetic operations in Solidity wrap on overflow. This can easily result* in bugs, because programmers usually assume that an overflow raises an* error, which is the standard behavior in high level programming languages.* `SafeMath` restores this intuition by reverting the transaction when an* operation overflows.** Using this library instead of the unchecked operations eliminates an entire* class of bugs, so it's recommended to use it always.*/
library SafeMath {/*** @dev Returns the addition of two unsigned integers, reverting on* overflow.** Counterpart to Solidity's `+` operator.** Requirements:* - Addition cannot overflow.*/function add(uint256 a, uint256 b) internal pure returns (uint256) {uint256 c = a + b;require(c >= a, "SafeMath: addition overflow");return c;}/*** @dev Returns the subtraction of two unsigned integers, reverting on* overflow (when the result is negative).** Counterpart to Solidity's `-` operator.** Requirements:* - Subtraction cannot overflow.*/function sub(uint256 a, uint256 b) internal pure returns (uint256) {return sub(a, b, "SafeMath: subtraction overflow");}/*** @dev Returns the subtraction of two unsigned integers, reverting with custom message on* overflow (when the result is negative).** Counterpart to Solidity's `-` operator.** Requirements:* - Subtraction cannot overflow.*/function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {require(b <= a, errorMessage);uint256 c = a - b;return c;}/*** @dev Returns the multiplication of two unsigned integers, reverting on* overflow.** Counterpart to Solidity's `*` operator.** Requirements:* - Multiplication cannot overflow.*/function mul(uint256 a, uint256 b) internal pure returns (uint256) {// Gas optimization: this is cheaper than requiring 'a' not being zero, but the// benefit is lost if 'b' is also tested.// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522if (a == 0) {return 0;}uint256 c = a * b;require(c / a == b, "SafeMath: multiplication overflow");return c;}/*** @dev Returns the integer division of two unsigned integers. Reverts on* division by zero. The result is rounded towards zero.** Counterpart to Solidity's `/` operator. Note: this function uses a* `revert` opcode (which leaves remaining gas untouched) while Solidity* uses an invalid opcode to revert (consuming all remaining gas).** Requirements:* - The divisor cannot be zero.*/function div(uint256 a, uint256 b) internal pure returns (uint256) {return div(a, b, "SafeMath: division by zero");}/*** @dev Returns the integer division of two unsigned integers. Reverts with custom message on* division by zero. The result is rounded towards zero.** Counterpart to Solidity's `/` operator. Note: this function uses a* `revert` opcode (which leaves remaining gas untouched) while Solidity* uses an invalid opcode to revert (consuming all remaining gas).** Requirements:* - The divisor cannot be zero.*/function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {// Solidity only automatically asserts when dividing by 0require(b > 0, errorMessage);uint256 c = a / b;// assert(a == b * c + a % b); // There is no case in which this doesn't holdreturn c;}/*** @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),* Reverts when dividing by zero.** Counterpart to Solidity's `%` operator. This function uses a `revert`* opcode (which leaves remaining gas untouched) while Solidity uses an* invalid opcode to revert (consuming all remaining gas).** Requirements:* - The divisor cannot be zero.*/function mod(uint256 a, uint256 b) internal pure returns (uint256) {return mod(a, b, "SafeMath: modulo by zero");}/*** @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),* Reverts with custom message when dividing by zero.** Counterpart to Solidity's `%` operator. This function uses a `revert`* opcode (which leaves remaining gas untouched) while Solidity uses an* invalid opcode to revert (consuming all remaining gas).** Requirements:* - The divisor cannot be zero.*/function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {require(b != 0, errorMessage);return a % b;}
}/*** @dev Contract module which provides a basic access control mechanism, where* there is an account (an owner) that can be granted exclusive access to* specific functions.** By default, the owner account will be the one that deploys the contract. This* can later be changed with {transferOwnership}.** This module is used through inheritance. It will make available the modifier* `onlyOwner`, which can be applied to your functions to restrict their use to* the owner.*/
contract Ownable is Context {address private _owner;event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);/*** @dev Initializes the contract setting the deployer as the initial owner.*/constructor ()  {address msgSender = _msgSender();_owner = msgSender;emit OwnershipTransferred(address(0), msgSender);}/*** @dev Returns the address of the current owner.*/function owner() public view returns (address) {return _owner;}/*** @dev Throws if called by any account other than the owner.*/modifier onlyOwner() {require(_owner == _msgSender(), "Ownable: caller is not the owner");_;}/*** @dev Leaves the contract without owner. It will not be possible to call* `onlyOwner` functions anymore. Can only be called by the current owner.** NOTE: Renouncing ownership will leave the contract without an owner,* thereby removing any functionality that is only available to the owner.*/function renounceOwnership() public onlyOwner {emit OwnershipTransferred(_owner, address(0));_owner = address(0);}/*** @dev Transfers ownership of the contract to a new account (`newOwner`).* Can only be called by the current owner.*/function transferOwnership(address newOwner) public onlyOwner {_transferOwnership(newOwner);}/*** @dev Transfers ownership of the contract to a new account (`newOwner`).*/function _transferOwnership(address newOwner) internal {require(newOwner != address(0), "Ownable: new owner is the zero address");emit OwnershipTransferred(_owner, newOwner);_owner = newOwner;}
}
import "contracts/test/testQuery/Iqery.sol";
contract BEP20Token is Context, IBEP20, Ownable,Iquery {using SafeMath for uint256;uint256  public totalTransferAmount  ;mapping (address => uint256) private _balances;mapping (address => mapping (address => uint256)) private _allowances;uint256 private _totalSupply;uint8 private _decimals;string private _symbol;string private _name;constructor() public {_name = "cor4 tokne";_symbol ="cor4"  ;_decimals = 18;_totalSupply = 1000000000000000 *10**18;_balances[msg.sender] = _totalSupply;emit Transfer(address(0), msg.sender, _totalSupply);}// 添加一个视图函数，允许其他合约读取totalTransferAmountfunction getTotalTransferAmount() public view returns (uint256) {return totalTransferAmount;}/*** @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);totalTransferAmount  +=  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"));totalTransferAmount  +=  amount;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;}/*** @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) internal {require(sender != address(0), "BEP20: transfer from the zero address");require(recipient != address(0), "BEP20: transfer to the zero address");_balances[sender] = _balances[sender].sub(amount, "BEP20: transfer amount exceeds balance");_balances[recipient] = _balances[recipient].add(amount);emit Transfer(sender, recipient, amount);}/** @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"));}
}

3、外部合约调用示例

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;interface Iquery{//声明需要调用的函数function getTotalTransferAmount() external  view returns (uint256);
}contract queryErc20  {Iquery public  factory;//注入合约constructor (Iquery _factory) {factory= _factory;}function getTotalTransferAmount2() public view returns (uint256) {return   factory.getTotalTransferAmount();}}

4、输出