Is there a way to move trigger logic into an apex class?  I want to add a few lines into a current trigger that references an apex class that does the logic.  I'm running into trouble when trying to replicate the trigger in a class, mainly when I get to the Trigger.new method, can this be called into an apex class, as well as the Trigger.oldmap?

Here is the logic in the trigger, which works fine, it creates a record into a related list if a field changes.

Any advise?  Will the logic be possible to put into a class and how would I use the trigger.oldmap and Trigger.New methods?

Below is the trigger and then below this is the class I am trying to move it too:

trigger FieldChangeTrigger on QuoteLineItem (after update) {

List <QLI_History_Tracking__c> history = new List <QLI_History_Tracking__c>();

for (QuoteLineItem qli : Trigger.new) {

if(qli.UnitPrice != Null && qli.UnitPrice != trigger.oldMap.get(qli.Id).UnitPrice)
{
history.add(new QLI_History_Tracking__c (
Quote_Line_Item__c = qli.Id,
Sales_Price_From__c = trigger.oldMap.get(qli.Id).UnitPrice,
Sales_Price_To__c = qli.UnitPrice
));
}

if(history.size() >0)
{
insert history;
}

}

Here is what I will be changing the trigger into:

trigger FieldChangeTrigger on QuoteLineItem (after update) {

//need to copy all relevant fields so they will always pick up previous values when one is changed
//object wil be called pricing history

if(Trigger.isUpdate && Trigger.isAfter){

managePricingHistory.afterupdate(Trigger.New);

}

An then the above trigger will reference this class

public with sharing class managePricingHistory {


public static list<QuoteLineItem> afterUpdate(list<QuoteLineItem> qli) {

List <QLI_History_Tracking__c> history = new List <QLI_History_Tracking__c>();

for (QuoteLineItem qlit : Trigger.new) {  

// I'm getting an error message here that says "Loop variable must be of type SObject

}

if(history.size() >0)
{
insert history;
}

return qli;
}

}