Simple CrowdsaleWithPresale contract

CrowdsaleWithPresale.sol

pragma solidity ^0.4.18;

import "zeppelin-solidity/contracts/crowdsale/price/IncreasingPriceCrowdsale.sol";

/**
 * @title CrowdsaleWithPresale
 * @dev Extension of IncreasingPriceCrowdsale contract that increases the price of tokens
 * once the specified period has elapsed (presale time).
 */
contract CrowdsaleWithPresale is IncreasingPriceCrowdsale {

  uint256 public presaleClosingTime;

  function CrowdsaleWithPresale(uint256 _presaleClosingTime) public {
    presaleClosingTime = _presaleClosingTime;
  }

  /**
   * @dev Checks whether the period in which the presale is open has already elapsed.
   * @return Whether presale period has elapsed
   */
  function presaleClosed() public view returns (bool) {
    return now > presaleClosingTime;
  }

  /**
   * @dev Returns the rate of tokens per wei at the present time.
   * Note that, as price _increases_ with time, the rate _decreases_.
   * @return The number of tokens a buyer gets per wei at a given time
   */
  function getCurrentRate() public view returns (uint256) {
    return presaleClosed() ? finalRate : initialRate;
  }

}