Workshop 202, Tutorial 3, Step 3, Apex

MobileInventoryExtension.cls

public class MobileInventoryExtension {

  // Constructors. Needed to use as an extension.
  public MobileInventoryExtension(ApexPages.StandardController c) {}
  public MobileInventoryExtension(ApexPages.StandardSetController c) {}

  // Remote Action function lets JavaScript call Apex directly 
  // method to update a given Merchandise record passed in from a Visualforce page JavaScript function
  @RemoteAction
  public static String updateMerchandiseItem(String productId, Integer newInventory) {
    // get the target Merchandise sObject
    List<Merchandise__c> m = [SELECT Id, Name, Price__c, Quantity__c from Merchandise__c WHERE Id =: productId LIMIT 1];
    // if found, try to update it with the new Quantity
    if(m.size() > 0) {
      m[0].Quantity__c = newInventory;
      try {
        update m[0];
        return 'Item Updated';
      }
      catch (Exception e) {
        return e.getMessage();
      }   
    }
    else {
      return 'No item found with that ID';
    }    
  }    
}