Design and Architecture

1-Oct-07 6:26

Hello,
I'm learning and trying to improve my object design skills, so please excuse my ignorance.

I've got a very basic app I'm working on that involves house windows. Each Window is composed of various options (frames, glass, screens etc). Each option has a unit mulitplier used to calculate prices. The window itself has size parameters height & width.

I don't know how to post a diagram, so here is a URL to a diagram of how I would typically design it.

http://www.mxpreview.com/ClassDiagram.pdf[^]

In my example, I would create three classes (window, windows, windowoptions).
The window class represents a single window. The window class has an arraylist propery of windowoption objects. In the window object I have a function that rolls through the windowoptions to calculate the cost of the window. The New() constructor is overloaded to accept an ID, which will load up the individual properties.

The windowoption object represent the various options a window might have. There is really no action done by the windowoption object. It is just used to calculate price.

The windows object is what I'd use to generate the various window objects.

QUESTION:
Am I headed the right direction? Is this a typical way of doing things? Is there any reason to make this more complex?

Any guidance will be greatly appreciated!

Thanks,

Wauna

stavinski2-Oct-07 22:37

stavinski

2-Oct-07 22:37

The design seems to ok, if i can make 2 suggestions:

1. Have the Window object use a separate object for performing database interaction this could be based on an interface something like IWindowGateway that would have methods to Insert(), Update(), Delete(). A concrete implementation of this could be passed in by constructor or by setting a property (or could be set by using a DI framework). This provides benefits of being able to perform unit tests against Window without DB interaction and also makes a little easier if you need to use another type of storage type.

2. Windows would maybe be better called something like WindowFinder that provides methods that returns lists of Window objects based on Criteria such as FindWindowByQuote(int quoteID) or FindWindowByCost(decimal minCost, decimal maxCost) etc.. as and when needed.

Hope this helps Smile | :)

Wauna3-Oct-07 8:40

3-Oct-07 8:40

Hi stavinski,
Thanks for your input. I think I understood what you suggested. I reworked my class diagram. Here is the link. I'm not 100% certain that I've got the diagram relations correct, but I think I understand what you suggested.

http://www.mxpreview.com/WindowClassDiagram2.jpg[^]

So, to handle db operations I would create a concrete object, and pass it to the constructor as a parameter. Then I could call MyWindowDB.Insert() which would roll through the parameters and perform the update. The advantage to doing this is that a database change would not require me to modify the "Window" class.
Does this seem correct? You mentioned testing, and I think I understood your logic on that. I wouldn't need to modify the database while testing validation and such.

Are there any other reasons to use this type of structure?

The CalculateCost() function would need to be in the interface. How would I keep that logic in one spot? I'm not sure if an interface can contain code like that function. I'm kind of new to this, so I apologize for the ignorance.

stavinski4-Oct-07 2:58

stavinski

4-Oct-07 2:58

Hi Wauna,

I was thinking something like this Class Diagram[^]

Wauna4-Oct-07 3:36

4-Oct-07 3:36

Ahhh.. the Gateway is the interface, not the Window. That makes more sense. So SQLServerWindowGateway would contain the Stored Proc calls. An instance of iWindowGateway would reside in the Window object. Then I suppose some parameter would need to be set to determine which Gateway to use (SQL vs Memory). I think I'm seeing the idea....Clever! We will have abstracted the Data reading and writing away from the core objects. The extra layer provides the flexibility to modify the db without interfering with the core objects.

It makes sense.

Thanks Steve!

stavinski4-Oct-07 3:43

stavinski

4-Oct-07 3:43

You got it! Smile | :)

A doubt about 3 tire architecture.

Russell Jones5-Oct-07 3:05

Russell Jones

5-Oct-07 3:05

also the abstraction allows you to come up with new gateways. let's say you've got the window object on your machine in a SQL DB but you connect your laptop to head office. You can now pass the window SOAPServerWindowGatewayObject and the window is synchronized with Head Office. Equally that could be an IPartListPrintOutGateway etc I'm sure the potential list is almost limitless.

Russ

thomas_joyee30-Sep-07 19:37

thomas_joyee

30-Sep-07 19:37

My boss told me to design a 3 tire architecture application. I am using C# asp.NET 2005. Since I don't have much idea about the 3 tire architecture, I designed one based on articles found in net. I don't know how much perfect it is. So I like to hear your opinion. I designed it like this.

I created a class library project for data layer named 'DL'. It contains 2 classes. First one is 'DLCommon', which is to declare protected variables of SqlConnection, SqlCommand, SqlDataAdapter est. Its constructor will read and store the connection string in a variable from the config file. The second class is 'DL', which drived the 'DLCommon' class. This class contains the functions to open database, excute sql and stored procedure. Its constructor will open the connection and store in a SqlConnection variable until the object is destroyed.

I created another class library for business layer named 'BL'. This project has several classes. Each class is used to write functions for a particular set of operations. For example I created a class in 'BL' named 'clsUser', which is to write functions for add, edit, and delete the users. These class using a variable of 'DL' class for database operations.

The presentation layer is a web project which using the variables of the classes in the business layer project.

Thomas

Re: A doubt about 3 tire architecture.

Magnus Salgo1-Oct-07 20:18

Magnus Salgo

1-Oct-07 20:18

Sounds ok

Normally you have a 3 tire Architecture to isolate things from each other

UI - User Interface
BL - Business lauer where you have all your business logic
DAL - Data access layer where the database acces is in

IO recommend you to also have a look on O/R mappers and specially Castle where you in your BL add some properties to your code and the O/R mapper is taking care of the mapping to the database

Getting started article http://www.castleproject.org/activerecord/gettingstarted/index.html

Magnus Sälgö
Sälgö Consulting AB, Sweden

Re: A doubt about 3 tire architecture.

Brady Kelly3-Oct-07 2:43

Brady Kelly

3-Oct-07 2:43

Your concept looks OK, but if your are really going to name classes DL and BL you are looking for trouble.

I do not believe they are right who say that the defects of famous men should be ignored. I think it is better that we should know them. Then, though we are conscious of having faults as glaring as theirs, we can believe that that is no hindrance to our achieving also something of their virtues. - W. Somerset Maugham

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Advance My Design Skills to the next level

Wauna30-Sep-07 4:27

30-Sep-07 4:27

Hi Everyone,
This is my first post on this board. I've been reading it for over a year now trying to soak up any information I can get.

MY QUESTION:
I need to learn better design skills, but I am a lone coder. Unfortunately, I work by myself so I don't have anyone to bounce ideas off or learn from. How can I take my design skills to the next level? What are your suggestions?

MY BACKGROUND:
Unfortunately, I have been programing for a career for over 10 years. I started with Basic on the Apple when I was a kid. I then began my career with VB, and have since moved onto VB.NET. I became MCSD certified in with Visual Studio 6. I have taken the MS classes on .NET, and have read a few books, but I don't feel like I've got the necessary knowledge to design good systems. I mean, my systems work, but I'm afraid if someone looked at them they'd say, "What the heck were you thinking?!?".
I started to read a book on OO Design, that was based on the Martin Fowler book, but it used Bears, Zoo animals, and flowers as the examples. I didn't find the application of these to be to clear. Most of the time, it doesn't seem like my systems call for complex patterns, but without outside eyes how do I know?

So is the answer reading the right book? Or is it seeking out skilled people to teach me?

Any advice would be greatly appreciated!

Regards,

Wauna

Pete O'Hanlon30-Sep-07 23:42

Pete O'Hanlon

30-Sep-07 23:42

As you are on your own, I would advise you to pick a reasonably complex problem that has a database, business logic and possibly multiple front-end options. Then, break down your code into the various areas, e.g. data access at the database end. At this point, you should have a reasonable idea about what you expect your system to be composed of, so you could use TDD (Test Driven Development) to take a crack at developing your system.

Normally, I would expect you to do a lot more design up front, but as this is for your benefit only and as a way to experiment with what works for you, you can get to the coding a bit earlier than you would in a real project. Think about what patterns are present in your project, and how you can layer your code for best effect. Then - ask questions here on CP.

Deja View - the feeling that you've seen this post before.

Spithas30-Sep-07 23:42

Spithas

30-Sep-07 23:42

A good start is to read the HeadFirst Design Pattern & Head First Object-Oriented Analysis & Design.Check those out at http://www.headfirstlabs.com/books.php.Contact me any time at stzo_2@msn.com

User 17164921-Oct-07 4:37

User 1716492

1-Oct-07 4:37

These people have a number of resources you will find helpful. To access some of them, you will need to register with them.

http://www.netobjectives.com/[^]

modified 1-Aug-19 21:02pm.

Magnus Salgo1-Oct-07 20:26

Magnus Salgo

1-Oct-07 20:26

Another good book about patterns is http://www.oreilly.com/catalog/hfdesignpat/

and also Jimmy Nilsson book where he is beeing like a pair programmer to you
http://weblogs.asp.net/fbouma/archive/2006/06/26/Applying-Domain_2D00_Driven-Design-and-Patterns-by-Jimmy-Nilsson.aspx

Magnus Sälgö
Sälgö Consulting AB, Sweden

Wauna4-Oct-07 3:39

4-Oct-07 3:39

Hi Everyone,
Thank you for all of your responses. It looks like there are lots of books and resources that would be good to review. I'm also going to try posting some of the basics here.

Thanks again!

Wauna