Castle Windsor IOC: Passing constructor parameters to child components

Question

Hello,

The following code is for demo purposes only.

Lets say i have 2 components (businessService, and dataService), and a UI class.

UI class needs a business service, businessService needs a dataService, and dataService relies on a connectionString.

Form the UI class i need to resolve the business service, so i am writing the below code:

var service = container.Resolve<BusinessService>(new { dependancy = "con string 123" }));

notice that dependancy is the connectionString constructor parameter.

But the above code is not working, saying that dataService expecting dependancy which was not satisified.

Can't create component 'dataService' as it has dependencies to be satisfied. dataService is waiting for the following dependencies:

Keys (components with specific keys) - dependancy which was not registered.

So as a workaround i am doing this:

var service = container.Resolve<BusinessService>(new { dataService = container.Resolve<IDataService>(new { dependancy = "123" }) });

But from design, coding style and many perspectives this is not a good way of doing it.

So please if you can advise why its not working in the simple way or you have a better workaround please share.

Answer 1

The behavior you see is by design.

There are a couple of ways to approach the problem, depending on how dynamic the value you want to pass down is.

The documentation does a pretty good job detailing it, so I won't reiterate that here.

Update

To clarity - Windsor does not pass inline arguments down the resolution pipeline. The reason for that is simple - doing so would break an abstraction. Calling code would have to implicitly know that your BusinessService depends on DataService which depends on connection string.

If you absolutely have to do it, than do make this explicit. That is do pretty much what you're doing - resolve the DataService with its dependency on connection string explicitly, and explicitly resolve BusinessService passing the DataService as dependency.

To make things really explicit (and nicer to use as well) I'd suggest using Typed Factory for that instead of directly calling the container

public interface IFactory
{
   IDataService ResolveDataService(string connectionString);
   IBussinessService ResolveBussinessService(IDataService dataService);
   // possibly release method for IBussinessService as well
}