Using class attributes instead of const constructor arguments

Question

I've made an application that supports plugins. At the moment, the plugin's base class implements an abstract class and supplies it with the name of the plugin (stuff omitted):

public class AppExecutePlugin : APlugin
{
    public AppExecutePlugin() : base("Application Execute")
    {

    }
    ... (other stuff here)
}

Now, I am thinking of naming plugins using custom attributes as so (don't care about syntactical errors):

[PluginName("Application Execute")]
public class AppExecutePlugin : APlugin
{
    public AppExecutePlugin()
    {

    }
}

Since I rarely use attributes for my own apps, I would like to know whether the second approach will lead to more abstract implementation or in general if it has pros comparing to my first approach.

Zdeslav Vojkovic · Accepted Answer · 2012-09-30 11:51:42Z

1

It will not lead to more abstract implementation (as it is hard to evaluate how this affects 'abstractness'), but it has a few benefits:

you don't need to instantiate plugins in order to read metadata - you can just read the attribute info using reflection
plugin instances don't need to add state (i.e. members) just for the sake of having metadata
you can easily add additional attributes, or extend this one, without polluting the plugin interface

E.g. my plugins look like this:

[Plugin("FriendlyName", Description = "..", Version = "1.0")]
[RequiresLicense("LicKey.XYZ")]
class MyPlugin : PluginBase {...}

Without attributes, I would need to add all of this info to base class constructor. Of course, you could always avoid it by having a method in your plugin interface like this:

public static PluginInfo GetPluginInfo()
{
   return new PluginInfo() { Name = "FriendlyName",
                             Description = "..", 
                             Version = "1.0",
                             License = "lickey.XYZ" };
}

You could execute it using reflection without instantiating the plugins, thus achieving the same as with attributes. I prefer attributes to this approach, as it feels a bit more declarative, but that might easily be just personal taste.

edited Sep 30, 2012 at 11:51

answered Sep 30, 2012 at 11:41

Zdeslav Vojkovic

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2 Comments

Odys Over a year ago

Thank you Zdeslav. Only con at the moment is that I cannot force a plugin to have attributes, whilst using const argument is possible.

Zdeslav Vojkovic Over a year ago

You are right, constructor approach has that advantage. Well, programming is full of trade offs.

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