re: Episode 005 - Dependency Injection - ASP.NET Core: From 0 to overkill VIEW POST

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re: I had ever done java and c# projects and know a little DI like spring. Later I select Ruby, when I do rails project I find I need DI to mock test, ...

Yeah, didn't do anything with Ruby myself, so can't make a good comparison.

Maybe we're lucky and there's another DEV member reading this that has experience in both and wants to chime in 🙂.

Welcome, happy to talk DI with you. I have the short ruby code to demo:

    class Factory  
      attr_accessor :product  
      def produce  
        @product.new  
      end  
    end  
    class Product  
      #..  
    end  
    fac = Factory.new  
    fac.product = Product  
    fac.produce  

Ah, I see, you create a factory and then use it instead of creating the Product directly.

In C# we normally use the dependency injection container as the factory (we still use factories on occasion, but for different reasons).

Using the container as the factory, and it being tightly integrated into the web framework, in the controllers, like you can see above, we just add the dependencies we want in the constructor, and the framework passes them in automatically.

public class GroupsController : Controller
{
    private readonly IGroupsService _groupsService;

    public GroupsController(IGroupsService groupsService)
    {
        _groupsService = groupsService;
    }

    //...
}
class PlayController < Controller

  def create(params)
     store = Invoice
     Invoice.generate_invoice(params, store)
     ... 
  end
end


In Ruby code is like this. Don't need a DI container.

Yupe. Different ways to get to the same end result of decoupling components 🙂

I like the C# approach, probably because I'm used to it, but I can understand that coming from other languages it seems overly complex.

Being able to just declare the dependencies in the constructor and they'll be there when running is nice (even if a bit magic) and gives quick visibility on the dependencies of a given class just by looking at the constructor. It does come with the hidden complexity you talked about, so as always, there are trade offs.

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