Ethereum Cookbook

How to do it…

1. Inherit the winnable DAL contract created in the previous recipe. Since the investments are usually handled using an ERC20 token, import the StandardToken contract from the openzeppelin library:

pragma solidity^0.4.23;import "./WinnableDAL.sol";import "./StandardToken.sol";contract InvestableDAL is WinnableDAL, StandardToken {    //...}

2. Create an invest function, which accepts investments from the user and allocates tokens accordingly:

function invest() public {    //...}

3. For simplicity, assume that each investor gets one token per Ether invested. Use the standard token functions to mint and allocate tokens:

address investor = msg.sender;uint tokens = msg.value;mint(investor, tokens);

4. Create a state variable to store the dividend ...