MobileInventoryExtension.cls

public class MobileInventoryExtension {
 
  public MobileInventoryExtension(ApexPages.StandardController c) {}
  public MobileInventoryExtension(ApexPages.StandardSetController c) {}
 
  @RemoteAction
  public static String updateMerchandiseItem(String productId, Integer newInventory) {
    List<Merchandise__c> m = [SELECT Id, Name, Price__c, Quantity__c from Merchandise__c WHERE Id =: productId LIMIT 1];
    if(m.size() > 0) {
      m[0].Quantity__c = newInventory;
      try {
        update m[0];
        return '更新されました';
      }
      catch (Exception e) {
        return e.getMessage();
      }   
    }
    else {
      return '指定されたIDに該当する商品がありません';
    }    
  }    
}