transfer->transferFrom() with explanation

refund.sol

@@ -109,7 +109,14 @@ contract Refund {
     function withdraw(DAO _dao) internal {
         uint balance = _dao.balanceOf(msg.sender);
 
-        if (!_dao.transfer(this, balance) || !msg.sender.send(balance * totalWeiSupply / totalSupply))
+        // The msg.sender must call approve(this, balance) beforehand so that
+        // transferFrom() will work and not throw. We need transferFrom()
+        // instead of transfer() due to the msg.sender in the latter ending
+        // up to be the contract
+        if (!_dao.transferFrom(msg.sender, this, balance)
+            || !msg.sender.send(balance * totalWeiSupply / totalSupply)) {
+
             throw;
+        }
     }
 }

refundBlack.sol

@@ -62,7 +62,14 @@ contract Refund {
     function withdraw(DAO dao) internal {
         uint balance = dao.balanceOf(msg.sender);
 
-        if (!dao.transfer(this, balance) || !msg.sender.send(balance * totalWeiSupply / totalSupply))
+        // The msg.sender must call approve(this, balance) beforehand so that
+        // transferFrom() will work and not throw. We need transferFrom()
+        // instead of transfer() due to the msg.sender in the latter ending
+        // up to be the contract
+        if (!dao.transferFrom(msg.sender, this, balance)
+            || !msg.sender.send(balance * totalWeiSupply / totalSupply)) {
+
             throw;
+        }
     }
 }

simpleRefund.sol

@@ -26,9 +26,15 @@ contract Refund {
 function withdraw(address donateExtraBalanceTo){
         uint balance = mainDAO.balanceOf(msg.sender);
 
-        if (!mainDAO.transfer(this, balance)
+        // The msg.sender must call approve(this, balance) beforehand so that
+        // transferFrom() will work and not throw. We need transferFrom()
+        // instead of transfer() due to the msg.sender in the latter ending
+        // up to be the contract
+        if (!mainDAO.transferFrom(msg.sender, this, balance)
             || !msg.sender.send(balance)
-            || !donateExtraBalanceTo.send(balance * totalWeiSupply / totalSupply - balance)
-           ) throw;
+            || !donateExtraBalanceTo.send(balance * totalWeiSupply / totalSupply - balance)) {
+
+            throw;
+        }
     }
 }