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A Modern Alternative to Abstract Factory Filtered Dependencies

· Integration Zone

The Integration Zone is brought to you in partnership with Red Hat. Use these flashcards along with the popular open source integration framework Apache Camel as an easy reference during the design and development of integration projects.

I've mentioned before that I really don’t like the Abstract Factory pattern, and in particular, code like this:

static IGUIFactory CreateOsSpecificFactory()
 {
    string sysType = ConfigurationSettings.AppSettings["OS_TYPE"];
    if (sysType == "Win") 
    {
        return new WindowsFactory();
    } 
    else 
    {
        return new MacFactory();
  }
}

One of the comments mentioned that this might not be ideal, but it is still better than:

if(RunningOnWindows)
 {
    // code
 }
 else if(RunningOnMac)
 {
    // code
 }
 else if(RunningOnLinux)
 {
    // code
}

And I agree. But I think that, as the comment mentioned, a far better alternative would be using the container. You can do this using:

[OperationSystem("Windows")]
public class WindowsFactory : IGUIFactory
{
} 
[OperationSystem("Linux")]
public class LinuxFactory : IGUIFactory
{
}
[OperationSystem("Mac")]
public class MacFactory : IGUIFactory
{
}

Then you just need to wire things through the container. Among other things, this means that we respect the open / closed principle. If we need to support a new system, we can just add a new class, we don’t need to modify code.

Remember, the Go4 book was written in the age of C++. Reflection didn’t exists, and that means that a lot of patterns do by hands things that can happen automatically.

 

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Published at DZone with permission of Ayende Rahien , DZone MVB .

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