CODEWITHSUNDEEP
design-patterns
El Duderino
El Duderino

Reputation:

Design pattern for this application?

You're writing an application that manages online courses. A course is completed in many different ways. A user must do one or more of the follow to complete the course:

When a course is completed, some event needs to happen. The event depends on the course. One or more of the following may need to happen:

Many of the courses are almost identical with respect to their requirements, but some are completely unique. There are a lot of courses, upwards of 50, and more are always being added.

How would you design an application like this? Is there a design pattern you can use to eliminate redundant code, and make it easy to add/edit courses?

Upvotes: 0

Views: 270

Answers (3)

AKS
AKS

Reputation: 1423

As there are fixed steps which are required for any course, then can we use Template pattern here? Like 

interface Course{
timeSpent();
testTaken();
lessonLearnt();
miscllenious();

}

All courses will implement this interface and implement the method accordingly. Please provide your views so that i can be clear whether I ahve understood it or not.

Upvotes: 0

bytebender
bytebender

Reputation: 7491

Here how I would start sketching it out...

You have a Course object which accepts a Requirements object and a OnCompleteActions object in its constructor... granted I would make the constructor internal and Create a CourseBuilder that will know how to build all of the different courses but...

When ever the Course is updated it checks if the Requirements are met by passing itself to the Requirements object. If it meets the requirements it then passes itself to the OnCompleteActions.

private void OnCourseUpdate()
{
        if (this._Requirements.AreMetBy(this))
        {
            this._OnCompleteActions.Execute(this);
        }
}

Requiremetns object is nothing but an aggregate list of IRequirement which you could fine tune based on the Course that you create... the AreMetBy method simple enumerates all of your IRequirements in the list and checks to see if your course satisfies them all...

interface IRequirement 
{
    public bool IsMetBy(Course course);
}

Then you could have all sorts of different Requirements that implement IRequirement...

class CourseHoursRequirement : IRequirement
{
    public CourseHoursRequirement(int minimumHours)
    {...}

    public bool IsMetBy(Course course)
    {
        return course.NumberHours >= this._MInimumHours 
    }
}

Same idea for the OnCompleteActions would have a list of one or More IOnCompleteAction that would execute each one. ex. CreateCertificateOnCompleteAction, SendEmailOnCompleteAction, etc.

By encapsulating each possible Requirement in its own class you can then Build a course that would have a MinimumHourRequirement, a PassedAllTestRequirement, etc. You could easily add new requirements as you go because they are all implementing the same interface. You probably have to add some limit properties as you go (like minimumHours) but the real work is done inside of the IsMetBy() method...

Good luck!

Upvotes: 1

fuzzy-waffle
fuzzy-waffle

Reputation: 830

A message bus for handling the final phase and a state machine to determine when they have passed. Actually all of this could be done with a message bus. A good book to read on it is Enterprise Integration Patterns which goes over situations like these. The tricky part is making sure that faults the software don't cause students to lose getting credit.

Maybe I just have jms/esb fever.

Upvotes: 1

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