Parameterized Factories Using Ninject

Question

How to make Ninject to instantiate object based on variable on run time?.

I am trying to inject the correct Repository in The Controller action - MVC 3 - based on parameter come from user input. If user input "BMW" it would bind ICarRepository to BMWRepository , and if he input "KIA" KiaRepository will be injected.

[HttpPost]
public ActionResult SearchResult(FormCollection values)
{
    string carModel  = values["model"];

    ICarRepository myRepository = RepositoryFactory.getRepository(carModel);

    .....
}

This is known by switch/case noob instantiation or Parameterized Factories, and i know how to do it manually without Ninject , Check the 4 approaches explained here Exploring Factory Pattern

My question is how to do it with Ninject?

Answer 1

You could inject an Abstract Factory (probably just a Func<string,ICarRepository>) and then have it all implemented via adding the following to your RegisterServices:

Bind<ICarRepository>().To<KiaRepository>().Named("KIA")
Bind<ICarRepository>().To<BmwRepository>().Named("BMW")
Bind<Func<string,ICarRepository>>()
    .ToMethod( ctx=> name => ctx.Get<ICarRepository>( name));

In your ctor:

class MyController
{
    readonly Func<string,ICarRepository> _createRepository;

    public MyController(Func<string,ICarRepository> createRepository)
    {
        _createRepository = createRepository;
    }

Then, in your action:

[HttpPost]
public ActionResult SearchResult(FormCollection values)
{
    string carModel  = values["model"];

     using( ICarRepository myRepository = _createRepository( carModel)) 
     {
            ... 
     } 
}