IoC container will upgrade your rank!

This post took some time to write. And I have to start with a confession. I didn’t use an IoC container (IoC stands for Inversion of Control) in my last example and I got scolded for it.

It’s not that I never worked with IoC containers before. But little experience as I had I always had everything configured long before I joined the projects. After receiving this critique I decided that it is the best chance to finally make up the shortcomings and make this legacy code better :-)

I won’t change the code from the last example much. As a matter of fact, only one section - Using the validators - will be changed.

I decided to use StructureMap to modify the examples.

• Declaring variables

Required NuGet package: StructureMap

First, we have to declare the IoC container:

private DI.Container _container;

I run into a reference problem and had to ensure that I point to StructureMap’s Container, which led me to this using:

using DI = StructureMap;

And then we need to initialize it:

Constructor() {
   _container = new DI.Container(c => { c.AddRegistry<OurRegistry>(); });  
}

Next, we create the registry…

Creating a registry

The registry is a class that inherits from the StructureMap.Registry.

It looks kind of like this:

using StructureMap;

namespace OurProject
{
  public class OurRegistry : Registry
  {
    public OurRegistry()
    {
      For<IValidateData>().Use<BirthDateValidator>();
      For<IValidateData>().Use<AddressValidator>();
      For<IValidateData>().Use<MinimumIncomeThisYearValidator>();

      For<IDataValidator>().Use<DataValidator>();
    }
  }
}

The IDataValidator is a new class responsible for launching all the validating rules. How is it different from the previous code?

namespace OurProject
{
  public class DataValidator : IDataValidator
  {
    private readonly IEnumerable<IValidateData> _validators;

    public DataValidator(IEnumerable<IValidateData> validators)
    {
      _validators = validators;
    }

    ...
  }
}

Previously, I used System.Reflection to get all the validation rules objects by their interfaces. Now, we just pass all of them as dependencies to the DataValidator. No additional logic is needed.

Using the IoC container

With the container declared, every time, we need an object we can use this line:

var fileParser = _container.GetInstance<IToBeInsuredParser>();

You do not have to pass anything to the constructor. The Registry takes care of that.

Summary?

Sorry if this post is too brief. It sure took a while to write it. Not to mention, that I have been playing a little with ASP.NET Core recently and learned that dependency injection is used there by default. It’s part of the architecture.

I suppose I’ll try to cover that next ;-)