Choosing the correct constructor using an external configuration file in Windsor?

Question

Hi,

I'm new to Windsor, but I'm certain there must be a way to do this...

I have a class with three different constructors:

public MyClass(string SomeParam)
{
...
}

public MyClass(string AnotherParam, string YetAnother)
{
...
}

public MyClass(string AnotherOne, string YeahIKnow, string AnnoyingExampleParam)
{
...
}

In my external configuration file, I have my service defined as:

<component
  id="IMyClass"
  service="IMyInterface, MyAssembly"
  type="MyClass, MyOtherAssembly">

  <parameters>
    <AnotherOne>string value #1</AnotherOne>
    <YeahIKnow>string value #2</YeahIKnow>
    <AnnoyingExampleParam>string value #3</AnnoyingExampleParam>
  </parameters>

</component>

When Windsor initializes an instance of my class, it only wants to initialize using the first (single string parameter) constuctor of my class, when I really want Windsor to use the third constructor.

I don't see anything in the docs about forcing the kernel to us a particular constructor using an external configuration, even though I can find references to doing it in code, but that sort of defeats the purpose of an external configuration!

Any advice would be appreciated.

Best,

David Montgomery

Answer 1

What version of Castle? I recall, from the depths of what goes for my memory at 4am in the morning, that there was a resolution for constructor work in Castle 2.0.

Humm, memory coming back a little now... Something tells me that Castle will construct the object with the first public ctor. May be as simple as moving what you want for Castle to load, to the top.

If that doesn't work for you, perhaps refactor your code a little?

Option 1) Make the first two constructors internal.

Option 2) Use a Factory pattern for your complex objects, which will utilize castle on the backend to new up the more simple or complex version.

Option 3) Create 3 classes from your base superclass, each having a more complicated constructor. This way, you can specific in the Castle config file exactly which service to load. For example:

public abstract class BaseClass
{
  public BaseClass(String requiredParam)
  {
    ...
  }
}

public class SimpleClass : BaseClass
{
  public SimpleClass(String requiredParam, String anotherParam)
    : base(requiredParam)
  {
    ...
  }
}


public class MoreComplexClass : SimpleClass 
{
  public MoreComplexClass (String requiredParam, String anotherParam, String yetAnother)
    : base(requiredParam, anotherParam)
  {
    ...
  }
}

But, I myself have not run into this yet. Mainly because I stick to only public 1 ctor on my classes, with a few private/internal ctors for things such as Linq to new up my objects with an empty ctor (since Linq doesn't support Dependency Injection, boo).

Note that in that last statement, internal ctors, that my SRP (Single Responsiblity Pattern) for resolving my IoC components is external, in a seperate higharchy assembly (i.e. an application or UI layer). Since it not internal to my domain objects, the internal ctors are not seen by Castle.

Answer 2

You must be doing something wrong.

Windsor uses the greediest constructor it can satisfy. If it uses the smaller one, you perhaps have some typo?

when your type is the service, you don't have to specify both

  service="MyClass, MyAssembly"
  type="MyClass">

remove the type.