Database Wrapper Objects

It’s common to use small wrapper objects around database tables. One object represents one row in the database table. For the sake of clarity the following is a simple example:

Database: Documents table, with columns (Id, FileName, Data). Where Id is an identifier for the object, I use a <a href=””>Guid</a&gt;.

A simple wrapper object for the Documents table would have the following pseudo code

class Document {
property Id
prpoerty FileName
property Data

The only issues are how to create new Document objects, how to save Document objects, and how to retrieve Document objects.

Since I’m young and stupid I had the wrong solution for all three problems.
First I created a separate Database class with static methods for Retrieving, Adding, & Updating Document objects. This becomes unmanageable when the number of wrapper objects for the database gets above 10.

The correct solution is to
1. Create a Save() method for the Document class that intelligently either adds the document to the database or updates the existing document in the database. Thus the user of the document class doesn’t need to remember if they’re updating an existing document or creating a new document.

2. Have a single constructor for the Document class that accepts an Id. This constructor then creates a new Document object if that Id does not exist in the database or retrieves the existing Document object from the database if that Id is in the database.

By doing the above the creation and saving of Document objects is entirely consistent. This reduces the cognitively load on users of the Document class so they don’t have to think about the details of how Document objects are created and stored, instead they can concentrate their effort on other things.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s