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I have generated a crowdsale contract and i want to add mincap to the crowdsale so that after reaching the mincap and not achieving the goal, the crowdsale will return all the funds to the investors.

Given Below is my Crowdsale code :

pragma solidity ^0.4.18;



contract ERC20Basic {
  uint256 public totalSupply;
  function balanceOf(address who) public view returns (uint256);
  function transfer(address to, uint256 value) public returns (bool);
  event Transfer(address indexed from, address indexed to, uint256 value);
}


library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    if (a == 0) {
      return 0;
    }
    uint256 c = a * b;
    assert(c / a == b);
    return c;
  }

  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    // assert(b > 0); // Solidity automatically throws when dividing by 0
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return c;
  }

  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    assert(b <= a);
    return a - b;
  }

  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}


contract Ownable {
  address public owner;


  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() public {
    owner = msg.sender;
  }


  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }


  /**
   * @dev Allows the current owner to transfer control of the contract to a newOwner.
   * @param newOwner The address to transfer ownership to.
   */
  function transferOwnership(address newOwner) public onlyOwner {
    require(newOwner != address(0));
    OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

}


contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  /**
  * @dev transfer token for a specified address
  * @param _to The address to transfer to.
  * @param _value The amount to be transferred.
  */
  function transfer(address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[msg.sender]);

    // SafeMath.sub will throw if there is not enough balance.
    balances[msg.sender] = balances[msg.sender].sub(_value);
    balances[_to] = balances[_to].add(_value);
    Transfer(msg.sender, _to, _value);
    return true;
  }

  /**
  * @dev Gets the balance of the specified address.
  * @param _owner The address to query the the balance of.
  * @return An uint256 representing the amount owned by the passed address.
  */
  function balanceOf(address _owner) public view returns (uint256 balance) {
    return balances[_owner];
  }

}


contract ERC20 is ERC20Basic {
  function allowance(address owner, address spender) public view returns (uint256);
  function transferFrom(address from, address to, uint256 value) public returns (bool);
  function approve(address spender, uint256 value) public returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) internal allowed;


  /**
   * @dev Transfer tokens from one address to another
   * @param _from address The address which you want to send tokens from
   * @param _to address The address which you want to transfer to
   * @param _value uint256 the amount of tokens to be transferred
   */
  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
    require(_to != address(0));
    require(_value <= balances[_from]);
    require(_value <= allowed[_from][msg.sender]);

    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
    Transfer(_from, _to, _value);
    return true;
  }

  /**
   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
   *
   * 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
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    Approval(msg.sender, _spender, _value);
    return true;
  }

  /**
   * @dev Function to check the amount of tokens that an owner allowed to a spender.
   * @param _owner address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint256 specifying the amount of tokens still available for the spender.
   */
  function allowance(address _owner, address _spender) public view returns (uint256) {
    return allowed[_owner][_spender];
  }

  /**
   * approve should be called when allowed[_spender] == 0. To increment
   * allowed value is better to use this function to avoid 2 calls (and wait until
   * the first transaction is mined)
   * From MonolithDAO Token.sol
   */
  function increaseApproval(address _spender, uint _addedValue) public returns (bool) {
    allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

  function decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
    uint oldValue = allowed[msg.sender][_spender];
    if (_subtractedValue > oldValue) {
      allowed[msg.sender][_spender] = 0;
    } else {
      allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
    }
    Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
    return true;
  }

}

contract TOKKA is StandardToken {
    string public name = "New Commercial Token";
    string public symbol = "NCT";
    uint256 public decimals = 18;

    uint256 constant INITIAL_SUPPLY = 6000000 * 10**18;
    function TOKKA () public {
       balances[msg.sender] = INITIAL_SUPPLY;
    }
}


contract Crowdsale is Ownable {
  using SafeMath for uint256;

   // The token being sold
  TOKKA public token;

  // start and end timestamps where investments are allowed (both inclusive)
  uint256 public startTime;
  uint256 public endTime;

  // address where funds are collected
  address public wallet;

  // how many token units a buyer gets per wei
  uint256 public rate;

  // amount of raised money in wei
  uint256 public weiRaised;

  uint256 public CAP = 3000000000000000000;

  bool crowdsaleClosed = false;

  event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);


  function Crowdsale(uint256 _startTime, uint256 _endTime, uint256 _rate, address _wallet) public {
    require(_startTime >= now);
    require(_endTime >= _startTime);
    require(_rate > 0);
    require(_wallet != address(0));

    startTime = _startTime;
    endTime = _endTime;
    rate = _rate;
    wallet = _wallet;
    token = createTokenContract();
  }

// creates the token to be sold.
// override this method to have crowdsale of a specific mintable token.
function createTokenContract() internal returns (TOKKA) {
    return new TOKKA();
  }


  // fallback function can be used to buy tokens
  function () external payable {
    buyTokens(msg.sender);
  }

  // low level token purchase function
function buyTokens(address beneficiary) public payable {
    require(beneficiary != address(0));
    require(validPurchase());
    require(!crowdsaleClosed);


    uint256 weiAmount = msg.value;

    // calculate token amount to be created
    uint256 tokens = weiAmount.mul(rate);

    // update state
    weiRaised = weiRaised.add(weiAmount);

    // transfer tokens purchased 
    //ERC20(token).transfer(this, tokens);
    //StandardToken(token).transfer(this, tokens);
    StandardToken(token).transfer(beneficiary, tokens);

    TokenPurchase(msg.sender, beneficiary, weiAmount, tokens);

    forwardFunds();
}


  function forwardFunds() internal {
    wallet.transfer(msg.value);
  }


  function validPurchase() internal view returns (bool) {
    bool withinPeriod = now >= startTime && now <= endTime;
    bool nonZeroPurchase = msg.value != 0;
    return withinPeriod && nonZeroPurchase;
  }


  function hasEnded() public view returns (bool) {
    return now > endTime;
  }

  function GoalReached() public view returns (bool) {

    return (weiRaised >= CAP);
  }

  function Pause() public onlyOwner
  {
       //if (weiRaised >= CAP){

        //}
        require(weiRaised >= CAP);

        crowdsaleClosed = true;
  }

  function Play() public onlyOwner
  {
       //if (weiRaised >= CAP){

        //}
        require(crowdsaleClosed == true);

        crowdsaleClosed = false;
  }

}

Any one can help me with this ?

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Create a mapping of the investor address and their investment, so mapping(msg.sender => msg.value) investors. Then create a mincap variable and once the crowdsale is over check if it has been reached. If not open a function which has been locked by a modifier which would allow users to withdraw their balance again.

  • can you please edit my given code and make changes to it ? Please share that code with me as I am new to blockchain. Thanks for your kind help – usman mehmood Mar 16 '18 at 14:39
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It looks like you're using quite a lot of OpenZeppelin's Smart Contract library - which is great - but why stop at just using the Crowdsale contract?

I would recommend looking at their RefundableCrowdsale contract:

@title RefundableCrowdsale
@dev Extension of Crowdsale contract that adds a funding goal, and
 * the possibility of users getting a refund if goal is not met.

after reaching the mincap and not achieving the goal

Although, I have to admit that this doesn't seem to make a lot of sense to me - I don't see the point in a "minicap"; just have the goal at the cutoff point for refunding (it's the same outcome).

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