473,326 Members | 2,104 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 473,326 software developers and data experts.

Circular Dependencies.

I have the following code (much simplified for this post). Note that
SessionKey uses DataAccess, and DataAccess requires SessionKey in it's
constructor.

Public Class SessionKey
Public IsValidSession as Boolean

Sub New(UserName, Password)
' Create session, including calls on DataAccess
' to validate username/password

IsValidSession = True
Dim DataAccess as New DataAccess(Me)

' Set IsValidSesion = False if usercode/password is invalid.

End Sub
End Class

Public Class DataAccess
Sub New(SessionKey)
If Not SessionKey.IsValidSession then
Throw New Exception ("Not a valid session!")
End If
End Sub

Function ExecuteSQL(SQL) As DataSet
'execute some SQL

End Function

End Class

It works great, but does this qualify as a circular dependency?
What's wrong with having a circular dependency in the first place?
Memory leaks? Performance problems? I understand that circular
dependencies can be a symptom of poorly designed class libraries, but
in this case, the class design seems fine. Should I take the time to
create a 3rd class that SessionKey and DataAccess inherit from?

Thanks,

Henry
Jul 21 '05 #1
1 2073
If you don't mind your class design, then it won't have a problem. Circular
dependencies can be a problem when the classes are in different assemblies.
Circular references used to be more a problem, but the GC handled them just
fine now. A recursive call might result in your classes if someone isn't
careful (suppose in one constructor, you call the other, and vice versa) --
however those will result in a stack overflow after taking full CPU for a
bit, so they'll be noticed when they happen.

-mike
MVP

"Henry Miller" <uw**@yahoo.com> wrote in message
news:49**************************@posting.google.c om...
I have the following code (much simplified for this post). Note that
SessionKey uses DataAccess, and DataAccess requires SessionKey in it's
constructor.

Public Class SessionKey
Public IsValidSession as Boolean

Sub New(UserName, Password)
' Create session, including calls on DataAccess
' to validate username/password

IsValidSession = True
Dim DataAccess as New DataAccess(Me)

' Set IsValidSesion = False if usercode/password is invalid.

End Sub
End Class

Public Class DataAccess
Sub New(SessionKey)
If Not SessionKey.IsValidSession then
Throw New Exception ("Not a valid session!")
End If
End Sub

Function ExecuteSQL(SQL) As DataSet
'execute some SQL

End Function

End Class

It works great, but does this qualify as a circular dependency?
What's wrong with having a circular dependency in the first place?
Memory leaks? Performance problems? I understand that circular
dependencies can be a symptom of poorly designed class libraries, but
in this case, the class design seems fine. Should I take the time to
create a 3rd class that SessionKey and DataAccess inherit from?

Thanks,

Henry

Jul 21 '05 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

12
by: jinal jhaveri | last post by:
Hi All, I have one question regarding circular inheritance I have 3 files 1) A.py , having module A and some other modules 2) B.py having module B and some other modules 3) C.py having...
8
by: Tim Tyler | last post by:
Like C, Python seems to insist I declare functions before calling them - rather than, say, scanning to the end of the current script when it can't immediately find what function I'm referring to. ...
2
by: ernesto basc?n pantoja | last post by:
Hi everybody: I'm implementing a general C++ framework and I have a basic question about circular dependencies: I am creating a base class Object, my Object class has a method defined as:...
3
by: Keith F. | last post by:
Visual Studio doesn't allow circular references between projects. I have a situation where I need to allow 2 projects to reference each other. Is there any way to make Visual Studio allow this? ...
1
by: Henry Miller | last post by:
I have the following code (much simplified for this post). Note that SessionKey uses DataAccess, and DataAccess requires SessionKey in it's constructor. Public Class SessionKey Public...
7
by: barias | last post by:
Although circular dependencies are something developers should normally avoid, unfortunately they are very easy to create accidentally between classes in a VS project (i.e. circular compile-time...
8
by: nyhetsgrupper | last post by:
I have written a windows service and want to expose a web based user interface for this service. I then wrote a class library containing a ..net remoting server. The class library have a method...
5
by: =?Utf-8?B?Qm9i?= | last post by:
I have a table of dependencies and want to check to see if the dependencies cause a circular reference. Any sugesstions on how to do this using c#. Example, ID DependsOnID 1 2 1 ...
6
by: Mosfet | last post by:
Hi, I have two classes, let's call them class A and class B with mutual dependencies as shown below and where implementation is inside .h (no cpp) #include "classB.h" class A {
0
by: DolphinDB | last post by:
Tired of spending countless mintues downsampling your data? Look no further! In this article, you’ll learn how to efficiently downsample 6.48 billion high-frequency records to 61 million...
0
by: ryjfgjl | last post by:
ExcelToDatabase: batch import excel into database automatically...
1
isladogs
by: isladogs | last post by:
The next Access Europe meeting will be on Wednesday 6 Mar 2024 starting at 18:00 UK time (6PM UTC) and finishing at about 19:15 (7.15PM). In this month's session, we are pleased to welcome back...
0
by: Vimpel783 | last post by:
Hello! Guys, I found this code on the Internet, but I need to modify it a little. It works well, the problem is this: Data is sent from only one cell, in this case B5, but it is necessary that data...
0
by: jfyes | last post by:
As a hardware engineer, after seeing that CEIWEI recently released a new tool for Modbus RTU Over TCP/UDP filtering and monitoring, I actively went to its official website to take a look. It turned...
0
by: ArrayDB | last post by:
The error message I've encountered is; ERROR:root:Error generating model response: exception: access violation writing 0x0000000000005140, which seems to be indicative of an access violation...
1
by: Defcon1945 | last post by:
I'm trying to learn Python using Pycharm but import shutil doesn't work
0
by: af34tf | last post by:
Hi Guys, I have a domain whose name is BytesLimited.com, and I want to sell it. Does anyone know about platforms that allow me to list my domain in auction for free. Thank you
0
by: Faith0G | last post by:
I am starting a new it consulting business and it's been a while since I setup a new website. Is wordpress still the best web based software for hosting a 5 page website? The webpages will be...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.