OpenZeppelin Pausable Contract – Pausable Contract in OpenZeppelin

icoopenzeppelintokens

I'm trying to create a crowdsale contract with open-zeppelin.

I want to pause the sale of tokens during the ICO period. I see there is this Pausable.sol which is to pause the contract (as per my understanding). I've called this pausable function in my crowdsale contract like the following:

contract SampleCrowdsale is CappedCrowdsale, Pausable {


  function SampleCrowdsale(uint256 _startTime, uint256 _endTime, uint256 _rate, uint256 _cap, address _wallet) public
    CappedCrowdsale(_cap)
    Crowdsale(_startTime, _endTime, _rate, _wallet)
  {

  }

  function createTokenContract() internal returns (MintableToken) {
    return new SampleCrowdsaleToken();
  }

}

After deploying the contract, , in the contract management page in Mist I can see the pause and unpause option. However, triggering them doesn't make any difference and the sale goes on. Am I doing something wrong here or this is not the way the pausable function works in opnezeppelin?

Best Answer

The Pausable contract you're inheriting from just adds pause and unpause, which updates a state variable paused. But that's all it does by itself.

You'll need to use the modifiers whenPaused and whenNotPaused in your contract. If you put whenNotPaused on a function, then that function won't be callable when the contract is in the paused state. (For example, you might want to put that on whatever function is selling people coins during your ICO.)

Related Solutions

Crowdsale Contract – How to Mint Tokens in Another Token Contract

Yes what you need to do is first create your token in a separate contract. Then when you create your crowdsale you pass in the constructor the address of your token.

This is a sample taken from the Ethereum Crowdfund your idea

pragma solidity ^0.4.16;

interface token {
    function mintToken(address receiver, uint amount);
}

contract Crowdsale {
    token public tokenReward;

    /**
     * Constrctor function
     */
    function Crowdsale(
        address addressOfTokenUsedAsReward
    ) {
        tokenReward = token(addressOfTokenUsedAsReward);
    }
}

ERC-20 – What is Pausable Token in ERC-20 OpenZeppelin

I assume you are referring to https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/token/ERC20/ERC20Pausable.sol .

It's a regular token which with an addition of pausing functionality. If the token contract is 'paused', nothing can be done with it (it can't be transferred). Only the one with 'pauser' access (whoever deployed the contract) can pause/unpause the contract - although it looks like multiple 'pauser' accounts can be added (https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/access/roles/PauserRole.sol).

Pausing is often used in for example emergencies - if there's a critical vulnerability in the code you can just pause its functionality and the vulnerability can't be abused until you figure out what to do about the problem.

On the other hand, if someone has such power over a token contract, it's very centralized and it's probably not going to be accepted in exchanges.

Best Answer

Related Solutions

Crowdsale Contract – How to Mint Tokens in Another Token Contract

ERC-20 – What is Pausable Token in ERC-20 OpenZeppelin

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