Tuesday, 13 March 2007

Fluent Specification Part 4: Prepacked Questions

I went to my client and demo'd the Bouncer application to him and he was happy so we rolled it out immediately but he did say that the direction of his business had changed recently and we needed to make a few changes.

A week later we met up and he excitedly told me all about how his entertainment service was doing really well but he was not getting the most potential out of his business as he was only open at weekends. What he wanted to do was be open 7 nights a week with different events each night. The problem is that on different events the rules around who to let in will change and my Bouncer isn't flexible enough to handle that at the moment. He really needs me to update the app as soon as to start ramping up his business.

So what we need to do is allow an event class to supply the questions which the bouncer will ask the clubbers. So we need some code like this:
Event tonightsEvent = new Event(new QuestionToAsk(IsClubber.YoungEnough(16), "under sixteens only mate")
.AndNot(IsClubber.WearingFancyDress(), "fancy dress only tonight");
foreach(Clubber clubber in queue.Clubbers)
Answer answer = clubber.Ask(tonightsEvent.EntryQuestions);
if(answer.IsFalse) ...

To achieve this we have to introduce a new class called a QuestionToAsk. This looks almost identical to the IQuestionSyntax except it has an Ask(T obj) method which returns a IQuestionSyntax instead of an Answer property (this is because the other question is being answered where as this one needs to be given to the clubber). This meant overriding the Ask() method of the clubber to look like this:

public IQuestionSyntax Ask(QuestionToAsk questionToAsk)
return questionToAsk.Ask(this);

So I implemented the new parts to my framework and checked that all my existing tests and new tests passed and rolled out the Bouncer to the client.

I'm sorry if I rushed the last couple of posts but there should be enough info to get the pattern off the ground. What I like is that I can use the fluent style to make sentances up which are easy to read and apply to objects.

No comments:

About Me

My photo
West Malling, Kent, United Kingdom
I am a ThoughtWorker and general Memeologist living in the UK. I have worked in IT since 2000 on many projects from public facing websites in media and e-commerce to rich-client banking applications and corporate intranets. I am passionate and committed to making IT a better world.