openzeppelin-contracts VS openzeppelin-solidity

Lets look the events of Open Zeppelin’s ERC20 token contract:

ERC-777 is difficult to implement properly, due to its susceptibility to different forms of attack(opens in a new tab). It is recommended to use ERC-20 instead. This page remains as a historical archive.

This depends if you're writing a contract from scratch or using existing code. If you're making something new, then yes (recommend not to use THE most recent available, always better to go with tried and tested). For existing projects, never try to override the solidity version. This may be a pain with "@" imports - ideally everyone should specify the library version (e.g. https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.5.1/contracts/token/ERC20/ERC20.sol).

pragma solidity ^0.5.0; import "https://github.com/OpenZeppelin/openzeppelin-solidity/contracts/math/SafeMath.sol"; contract MyContract { using SafeMath for uint256; function deposit() public payable { // code to deposit ether } function withdraw(uint256 _amount) public { require(this.balance.sub(_amount) >= 0, "Insufficient funds"); // code to withdraw ether } }

The basic structure could be done as follows using OZ ERC20 interface https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/token/ERC20/IERC20.sol

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) { require(b <= a, "SafeMath: subtraction overflow"); 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-solidity/pull/522 if (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) { // Solidity only automatically asserts when dividing by 0 require(b > 0, "SafeMath: division by zero"); uint256 c = a / b; // assert(a == b * c + a % b); // There is no case in which this doesn't hold return 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) { require(b != 0, "SafeMath: modulo by zero"); return a % b; }

// See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522