allow custom rate function in crowdsales

contracts/crowdsale/Crowdsale.sol

@@ -24,9 +24,6 @@ contract Crowdsale {
   // 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;
 
@@ -40,26 +37,25 @@ contract Crowdsale {
   event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
 
 
-  function Crowdsale(uint256 _startBlock, uint256 _endBlock, uint256 _rate, address _wallet) {
+  function Crowdsale(uint256 _startBlock, uint256 _endBlock, address _wallet) {
     require(_startBlock >= block.number);
     require(_endBlock >= _startBlock);
-    require(_rate > 0);
     require(_wallet != 0x0);
 
     token = createTokenContract();
     startBlock = _startBlock;
     endBlock = _endBlock;
-    rate = _rate;
     wallet = _wallet;
   }
 
+  function getRate() returns (uint256);
+
   // creates the token to be sold. 
   // override this method to have crowdsale of a specific mintable token.
   function createTokenContract() internal returns (MintableToken) {
     return new MintableToken();
   }
 
-
   // fallback function can be used to buy tokens
   function () payable {
     buyTokens(msg.sender);
@@ -73,7 +69,7 @@ contract Crowdsale {
     uint256 weiAmount = msg.value;
 
     // calculate token amount to be created
-    uint256 tokens = weiAmount.mul(rate);
+    uint256 tokens = weiAmount.mul(getRate());
 
     // update state
     weiRaised = weiRaised.add(weiAmount);

contracts/crowdsale/FixedRate.sol

@@ -0,0 +1,15 @@
+pragma solidity ^0.4.11;
+
+import './Crowdsale.sol';
+
+contract FixedRate is Crowdsale {
+  uint256 rate;
+
+  function FixedRate(uint256 _rate) {
+    rate = _rate;
+  }
+
+  function getRate() returns (uint256) {
+    return rate;
+  }
+}

test/Crowdsale.js

@@ -9,7 +9,7 @@ const should = require('chai')
   .use(require('chai-bignumber')(BigNumber))
   .should()
 
-const Crowdsale = artifacts.require('Crowdsale')
+const Crowdsale = artifacts.require('./helpers/CrowdsaleImpl.sol')
 const MintableToken = artifacts.require('MintableToken')
 
 contract('Crowdsale', function ([_, investor, wallet, purchaser]) {

test/helpers/CappedCrowdsaleImpl.sol

@@ -2,9 +2,10 @@ pragma solidity ^0.4.11;
 
 
 import '../../contracts/crowdsale/CappedCrowdsale.sol';
+import '../../contracts/crowdsale/FixedRate.sol';
 
 
-contract CappedCrowdsaleImpl is CappedCrowdsale {
+contract CappedCrowdsaleImpl is CappedCrowdsale, FixedRate {
 
   function CappedCrowdsaleImpl (
     uint256 _startBlock,
@@ -13,8 +14,9 @@ contract CappedCrowdsaleImpl is CappedCrowdsale {
     address _wallet,
     uint256 _cap
   )
-    Crowdsale(_startBlock, _endBlock, _rate, _wallet)
+    Crowdsale(_startBlock, _endBlock, _wallet)
     CappedCrowdsale(_cap) 
+    FixedRate(_rate)
   {
   }
 

test/helpers/CrowdsaleImpl.sol

@@ -0,0 +1,19 @@
+pragma solidity ^0.4.11;
+
+import '../../contracts/crowdsale/Crowdsale.sol';
+import '../../contracts/crowdsale/FixedRate.sol';
+
+contract CrowdsaleImpl is Crowdsale, FixedRate {
+
+  function CrowdsaleImpl (
+    uint256 _startBlock,
+    uint256 _endBlock,
+    uint256 _rate,
+    address _wallet
+  )
+    Crowdsale(_startBlock, _endBlock, _wallet)
+    FixedRate(_rate)
+  {
+  }
+
+}

test/helpers/FinalizableCrowdsaleImpl.sol

@@ -2,18 +2,20 @@ pragma solidity ^0.4.11;
 
 
 import '../../contracts/crowdsale/FinalizableCrowdsale.sol';
+import '../../contracts/crowdsale/FixedRate.sol';
 
 
-contract FinalizableCrowdsaleImpl is FinalizableCrowdsale {
+contract FinalizableCrowdsaleImpl is FinalizableCrowdsale, FixedRate {
 
   function FinalizableCrowdsaleImpl (
     uint256 _startBlock,
     uint256 _endBlock,
     uint256 _rate,
     address _wallet
   )
-    Crowdsale(_startBlock, _endBlock, _rate, _wallet)
+    Crowdsale(_startBlock, _endBlock, _wallet)
     FinalizableCrowdsale() 
+    FixedRate(_rate)
   {
   }
 

test/helpers/RefundableCrowdsaleImpl.sol

@@ -2,9 +2,10 @@ pragma solidity ^0.4.11;
 
 
 import '../../contracts/crowdsale/RefundableCrowdsale.sol';
+import '../../contracts/crowdsale/FixedRate.sol';
 
 
-contract RefundableCrowdsaleImpl is RefundableCrowdsale {
+contract RefundableCrowdsaleImpl is RefundableCrowdsale, FixedRate {
 
   function RefundableCrowdsaleImpl (
     uint256 _startBlock,
@@ -13,8 +14,9 @@ contract RefundableCrowdsaleImpl is RefundableCrowdsale {
     address _wallet,
     uint256 _goal
   )
-    Crowdsale(_startBlock, _endBlock, _rate, _wallet)
+    Crowdsale(_startBlock, _endBlock, _wallet)
     RefundableCrowdsale(_goal) 
+    FixedRate(_rate)
   {
   }