在合约中调用一个已经存在的合约。

		
pragma solidity ^0.4.24;

/******************************************/
/*      Netkiller Crowdsale Contract      */
/******************************************/
/* Author netkiller <netkiller@msn.com>   */
/* Home http://www.netkiller.cn           */
/* Version 2018-06-07 - Solc ver: 0.4.24  */
/******************************************/

interface token {
	function balanceOf(address _address) constant external returns (uint256);
    function transfer(address receiver, uint amount) external;
}

contract Netkiller {
    
    token public tokenContract;

    constructor(address addressOfToken) public {
        tokenContract = token(addressOfToken);
    }
	function getBalance(address _address) view public returns (uint256){
        return tokenContract.balanceOf(_address);
    }
    function transfer(address _to, uint256 _value) payable public{
        tokenContract.transfer(_to, _value);
    }

    
}