Final Project Apex

requirement1

//*REQUIREMENT 1* Before a Stock Item can be created, check that there is not already
    // a stock item record with a matching name.
    
    //the below creates the new stockitems in a set that 
    //doesn't allow for duplicates. Trigger.new to ensure all new records created
    //for this object get added to this Set
    
    set <string> stockitems = new set <string> ();
    for (stock_item__c stock : trigger.new) {
        stockitems.add(stock.Item_Name__c);      
    }
    
    
//here we are checking for duplicates in the existing records to ensure
//we don't enter new stock items with the same name

    //SOQL query to get a list of existing stock items from the org calling for the stock name
    list <stock_item__c> stocklist = new list <stock_item__c> (
    [select id, Item_Name__c from stock_item__c where Item_Name__c in : stockitems]);
    
    
    for(stock_item__c newstock : trigger.new) {
        
        //checking if the list has a duplicate item then add the below words to the new stock item name
        if(stocklist.size() > 0)
            newstock.adderror('duplicate item' + newstock.Item_Name__c);
    }