c# - Implementing plugin Instance property for internal scoped code

Question

i've created my own plugin architecture for one of my programs.

Basicly Plugin is the base class for all of my plugins and say that i've plugins like PluginA : Plugin, PluginB : Plugin.

public class Plugin 
{
    private static Plugin _instance;
    public static Plugin Instance { get { return Plugin._instance; } }
}

Now as usual each of my plugins have other stuff like forms and other classes. From that classes i want to access the current plugin instance like;

Plugin.Instance.Settings()

If i do assign _instance field in plugin ctor like;

public Plugin(GlobalSettings gs, PluginSettings ps)
{
    Plugin._instance=this;
}

Then for each loaded plugin the Instance is overwritten and i get strange results like PluginB.Instance returning an instance of PluginA.

I know singleton does not seem the quite right way to do this, but i wasn't be able to come with another solution. Maybe a multiton can solve this, but i don't want my plugin writers to go for

Plugin.Instance["PluginB"]

all time which seems irrelevant.

Thanks for any help.

Gerrie Schenck · Answer 1 · 2010-11-12T15:03:57.140

0

Remove the static keyword and keep a List<Plugin> to loop over them.

edited Nov 12 '10 at 15:03

answered Nov 12 '10 at 14:58

Gerrie Schenck

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I don't want plugins to see each other's instances. – HuseyinUslu Nov 12 '10 at 15:05
and i remove the static keyword, the plugin helper classes will not be able to access it. – HuseyinUslu Nov 12 '10 at 15:14

Richard Friend · Accepted Answer · 2010-11-12T15:45:54.170

As suggested, you should store these in a List of some sort, possibly in the hosting application or possibly in the library.

You already have a reference to the current plugin, with the 'this' keyword, simply pass this into your other classes via constructor or methods :

like

public class MyPlugin :Plugin
{
    private MyClass myClass;

    public MyPlugin()
    {
         this.myClass = new MyClass(this);  
         this.myClass.DoSomething();
    }
    public void Something()
    {
         //Called back into from MyClass

    }
}
public class Myclass
{
     public Plugin OwnerPlugin {get;internal set;}
     public MyClass(Plugin ownerPlugin)
     {
           this.OwnerPlugin = ownerPlugin;
     }
     public void DoSomething()
     {
          //do something with ownerplugin
          this.OwnerPlugin.Something();
     } 
}

yea that's a solutin but the problem with that method is -- let me explain; I've a plugin called LibEvents which reads some events from an xml source and it contains lots of entries. I thought passing all the plugin instances tho that events was nonsense and from a plugin-developers of view may be somewhat making things complex. — HuseyinUslu, Nov 12 '10 at 15:46

c# - Implementing plugin Instance property for internal scoped code

2 Answers2