Having outlined an approach, even if its not a approapriate one, we are now intrested in seeing a better solution that is much cleaner than the previous one.

As we re-collect from the previous post our generalized problem was, "There is a addition to behaviour in some scenarios".

We decided to use a Decorator.

What we did was created a interface called IWebPageGenerator, which had a method Generate. Now, the original class was made to  implement from the interface IWebPageGenerator.And all the calls we initiated in the original class was from the Generate Method.

As for the scenario which required a Security check what we did was,

/*           SecurityDecorator                    */

public class SecurityDecorator:IWebPageGenerator{

      public IWebPageGenerator ChildWebPageGenerator {get; private set;}

      public SecurityManager _securityManager;

      public SecurityDecorator(IWebPageGenerator childWebPageGenerator){

             ChildWebPageGenerator = childWebPageGenerator;

             _securityManager = SecurityManager.Instance.Context(Privelege.Metadata.Update);

      }

      public string Generate(){

             _securityManager.Verify();

             return ChildWebPageGenerator.Generate();  

      }

}

/*               Usage                            */

var  webPageGenerator = new SecurityDecorator(webPageGenerator);

/*                                                */

As you can see what this approach brings in is lesser number of code changes. And a more cleaner code base. And the bonus is a better infrastructure of Web Pages Generator which is flexible and extensible.

- Till then Happy Coding :)

As I mentioned in the previous post, we choose the path of Refactoring the code to rectify the problem we were facing.

Let me restate the problem:

"We have a application where in there is a process called publish. What publish does is,

• It generates/prepares the XML of the Business Entities.
• That XML is the Model. This model is given to the Generator
• The Generator,generates DTO's and generates API for them.
• Then the request goes to the Render library, where in the Webpages or the UI is generated.
• Then the SQL Scripts are generated and then they are run against the database.

All this happens inside a Transaction so that we can rollback in case of error.

All was hanky dory untill recently.  The Web Page generator store is used from couple of other places. So due those scenarios, we had to introduce a check for security before allowing it to be generated. "

Let me generalize the problem a bit more. There is a addition to behaviour in some scenarios.What are the probable ways in solving this problem?

An if condition, which takes a decision on basis of a context variable whether Verify needs to be called

For Example:

//... do something

if(!_publishUnderProgress) _securityManager.Verify();

//... do something

Problems:

We might have to add few more conditions, or few more checks if the same class is used in a different context.

Notice the number of places where our logic is scattered.

• Establish Context From the Publisher Not to Use Verify
• Establish Context From other locations to Use Verify.
• Make changes in the WebPageGenerator

Bottom line is, its not a clean solution.

We will outline a better way of solving it the next time.

 

Most of the interviews that we generally tend to attend, we always try to make sure, that we are going for a job role, where in the kind of work is more towards development. And I myself have done this. But untill, recently, there was a task, that had been already written, and it badly needed extension. This piece of code which was already built was doing what it was meant for, effectively.

But the changes that were required, had few contracdictions with its essential design or the core design. Now the challenge was to get the piece moving or doing which it was already doing and then on top of it, add few more extensions to it. A typical maintenance scenario... 

I just questioned my self, was it that I was afraid to tackle such a situation earlier or whether, it was like, i was ignorant of this aspect of Software development. Just to brighten up this idea, I would start up a series to take scenarios and then try to make changes to it and learn and understand the underlying principles of the same...

Happy Coding!