Understanding Abstract Factory Pattern

[RSH]

Hi,

I am a fairly seasoned developer and have recently started looking at
software design patterns. I am starting with the Abstract Factory Pattern
and was wondering if someone could help me understand where I might use this
Pattern. I get the general concept but I am having a hard time converting
that concept into where I might use that in a real world scenerio for a
business application or web development project.

I appreciate the fact that this is a conceptual question, and I appreciate
your time.

Thank you!
Ron

[Jon Skeet [C# MVP]]

On May 15, 1:21 pm, "RSH" <way_beyond_o.. [e-mail] e:

I am a fairly seasoned developer and have recently started looking at
software design patterns. I am starting with the Abstract Factory Pattern
and was wondering if someone could help me understand where I might use this
Pattern. I get the general concept but I am having a hard time converting
that concept into where I might use that in a real world scenerio for a
business application or web development project.

Suppose you had encapsulated your data access into an interface, and
had implemented that interface for Oracle, SQL Server etc.

The abstract factory pattern would give you a central factory to call
which would in turn call the appropriate concrete factory depending on
configuration.

At least, that's the way I understand it.

Jon

[Mark Rae]

"Jon Skeet [C# MVP]" <sk***@pobox.co mwrote in message
news:11******** *************@q 75g2000hsh.goog legroups.com...

Suppose you had encapsulated your data access into an interface, and
had implemented that interface for Oracle, SQL Server etc.

The abstract factory pattern would give you a central factory to call
which would in turn call the appropriate concrete factory depending on
configuration.

At least, that's the way I understand it.

Yes indeed.

What happens when you add a provider that's not part of the "standard" .NET
Framework, e.g. MySQL or SqlCe...?

If your DAL factory includes SqlClient, Oracle *and* MySQL and you try to
run it on a machine which doesn't have the MySQL .NET native data provider,
won't your app fall over due to missing references etc...?
--
http://www.markrae.net

[Jon Skeet [C# MVP]]

On May 15, 1:49 pm, "Mark Rae" <m...@markNOSPA Mrae.netwrote:

At least, that's the way I understand it.

Yes indeed.

What happens when you add a provider that's not part of the "standard" .NET
Framework, e.g. MySQL or SqlCe...?

If your DAL factory includes SqlClient, Oracle *and* MySQL and you try to
run it on a machine which doesn't have the MySQL .NET native data provider,
won't your app fall over due to missing references etc...?

I believe the references will only be fetched when they're first
actively used. That's what I'd hope, anyway - I haven't actually tried
it :)

I'm sure with suitable levels of indirection it should be okay.

Jon

[RSH]

I almost understand that.

Are there any tutorials you know of that illustrate this concept?

Thanks,
Ron
"Jon Skeet [C# MVP]" <sk***@pobox.co mwrote in message
news:11******** *************@q 75g2000hsh.goog legroups.com...

On May 15, 1:21 pm, "RSH" <way_beyond_o.. [e-mail] e:

>I am a fairly seasoned developer and have recently started looking at
software design patterns. I am starting with the Abstract Factory
Pattern
and was wondering if someone could help me understand where I might use
this
Pattern. I get the general concept but I am having a hard time
converting
that concept into where I might use that in a real world scenerio for a
business application or web development project.

Suppose you had encapsulated your data access into an interface, and
had implemented that interface for Oracle, SQL Server etc.

The abstract factory pattern would give you a central factory to call
which would in turn call the appropriate concrete factory depending on
configuration.

At least, that's the way I understand it.

Jon

[Mark Rae]

"Jon Skeet [C# MVP]" <sk***@pobox.co mwrote in message
news:11******** *************@h 2g2000hsg.googl egroups.com...

I believe the references will only be fetched when they're first
actively used. That's what I'd hope, anyway - I haven't actually tried
it :)

Hmm - I'm sure that's correct, although I've never tried it either!

I'm sure with suitable levels of indirection it should be okay.

All my work tends to be targeted at one specific RDBMS - I've never been
asked to write anything which supported multiple providers...

Therefore, I have four quite separate DALs - SqlClient, OleDb, MySql and
most recently SqlCe...

I guess an abstract factory pattern might be more efficient as far as
development goes, but I'm not sure there's much point in a client receiving
a bespoke app with redundant code...
--
http://www.markrae.net

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

Buy the Design Pattern book :
http://www.amazon.com/Design-Pattern...9238351&sr=8-1

There you will find a good example of how to use each pattern based on a
Text Editor.

IIRC the example there is to how to handle different UI libraries without
modifying the code, let's say you want a program to run on MacOS, Win,
Linux, etc. You know that each of these system implement the same set of
controls (TextBox, CheckBox, ListBox,etc)
in such a way that you can declare an anbstract class (or inteface).

Your code does not need to know which one especifically is being used. It
just request an instance of ITextbox and the factory returns an instance of
it. Depending of what library is in used you get a instance of a Textbox of
the running system(MacOS, Win, Linux).

Take also a look at wikipedia, they have good articles explaining the
differents patterns.
"RSH" <wa************ *@yahoo.comwrot e in message
news:eB******** ******@TK2MSFTN GP03.phx.gbl...

Hi,

I am a fairly seasoned developer and have recently started looking at
software design patterns. I am starting with the Abstract Factory Pattern
and was wondering if someone could help me understand where I might use
this Pattern. I get the general concept but I am having a hard time
converting that concept into where I might use that in a real world
scenerio for a business application or web development project.

I appreciate the fact that this is a conceptual question, and I appreciate
your time.

Thank you!
Ron

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

"RSH" <wa************ *@yahoo.comwrot e in message
news:eS******** ******@TK2MSFTN GP03.phx.gbl...

>I almost understand that.

Are there any tutorials you know of that illustrate this concept?

The original book (see my other email) about Design pattern has a very
extense example using a Text Editor.

Also google for the desired pattern and you will get several examples

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

"Mark Rae" <ma**@markNOSPA Mrae.netwrote in message
news:%2******** ********@TK2MSF TNGP03.phx.gbl. ..

"Jon Skeet [C# MVP]" <sk***@pobox.co mwrote in message
news:11******** *************@q 75g2000hsh.goog legroups.com...

>Suppose you had encapsulated your data access into an interface, and
had implemented that interface for Oracle, SQL Server etc.

The abstract factory pattern would give you a central factory to call
which would in turn call the appropriate concrete factory depending on
configuratio n.

At least, that's the way I understand it.

Yes indeed.

What happens when you add a provider that's not part of the "standard"
.NET Framework, e.g. MySQL or SqlCe...?

If your DAL factory includes SqlClient, Oracle *and* MySQL and you try to
run it on a machine which doesn't have the MySQL .NET native data
provider, won't your app fall over due to missing references etc...?

Yes, it will fail at runtime. It will fail when you first try to use it

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

"Jon Skeet [C# MVP]" <sk***@pobox.co mwrote in message
news:11******** *************@h 2g2000hsg.googl egroups.com...

On May 15, 1:49 pm, "Mark Rae" <m...@markNOSPA Mrae.netwrote:

At least, that's the way I understand it.

Yes indeed.

What happens when you add a provider that's not part of the "standard"
.NET
Framework, e.g. MySQL or SqlCe...?

If your DAL factory includes SqlClient, Oracle *and* MySQL and you try to
run it on a machine which doesn't have the MySQL .NET native data
provider,
won't your app fall over due to missing references etc...?

I believe the references will only be fetched when they're first
actively used. That's what I'd hope, anyway - I haven't actually tried
it :)

You are correct, I have one app that use VFP and when I install it on a
machine without the OLEDB provider I get the error when I first try to use
the provider.