SXA custom component looking for parameterless constructor

Question

I am trying to create my first SXA compatible component, and I can't seem to get everything setup quite right. I decompiled the Maps component, and am using it as my guide. I understand that I need to use an MVC pattern, and so here's what I've got. Here's my controller:

public class OoyalaController : StandardController
{
    private readonly IOoyalaRepository _repository;
    public OoyalaController(IOoyalaRepository repository)
    {
        _repository = repository;
    }

    protected override object GetModel()
    {
        return _repository.GetModel();
    }
}

Here's my Interface:

public interface IOoyalaRepository : IModelRepository
{
}

And here's my repository class:

public class OoyalaComponentRepository: ModelRepository, IOoyalaRepository
{
    public override IRenderingModelBase GetModel()
    {
        OoyalaComponentModel model = new OoyalaComponentModel();
        FillBaseProperties(model);
        return model;
    }
}

Finally, here's my model class:

public class OoyalaComponentModel : RenderingModelBase
{
    public string MediaID { get; set; }
}

I've got my .cshtml looking like this:

@using Sitecore.XA.Foundation.SitecoreExtensions.Extensions
@model Components.Models.OoyalaComponentModel

<div class="component simple-component @Model.CssClasses.Aggregate()">
    <div class="component-content">
        <h1>You are on @Model.MediaID page</h1>
    </div>
</div>

In my content editor view, I believe I have the new rendering added to the right category and setup in the same way that the Map component is setup, as you can see in this screenshot:

I also setup the Parameters template to include the IComponentVariant and Styling base templates:

I seem to be missing something, however, as whenever I try to add my component to the page, I get the following error:

Exception: System.InvalidOperationException
Message: An error occurred when trying to create a controller of type 'Components.Controllers.OoyalaController'. Make sure that the controller has a parameterless public constructor.
Source: System.Web.Mvc
   at System.Web.Mvc.DefaultControllerFactory.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType)
   at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName)
   at Sitecore.Mvc.Controllers.SitecoreControllerFactory.CreateController(RequestContext requestContext, String controllerName)

Nested Exception

Exception: System.MissingMethodException
Message: No parameterless constructor defined for this object.
Source: mscorlib
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at System.Web.Mvc.DefaultControllerFactory.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType)

I understand that the system is looking for a parameterless constructor, however, the map component doesn't have a parameterless constructor.

What do I have configured/coded incorrectly?

Answer 1

To inject something via constructor or get types with Service Locator you need to register your services first.

public class RegisterOoyalaServices : IocProcessor
{
    public override void Process(IocArgs args)
    {
        args.ServiceCollection.AddTransient<IOoyalaRepository, OoyalaComponentRepository>();
    }
}

<pipelines>
  <ioc>
    <processor type="NAMESPACE.RegisterOoyalaServices, NAMESPACE" />
  </ioc>
</pipelines>

You will have to reference following DLLs:

• Sitecore.XA.Foundation.IoC
• Microsoft.Extensions.DependencyInjection
• Microsoft.Extensions.DependencyInjection.Abstractions

Answer 2

Ok - please don't use ServiceLocator to "fix" this issue. The problem looks to be because you have not registered your OoyalaController with your IoC container.

If you are using the standard Sitecore 8.2 container you can do this by creating a configurator for your project. You should also register your dependencies that the controller is requesting.

using Microsoft.Extensions.DependencyInjection;
using Sitecore.DependencyInjection;

namespace MyProject
{
    public class MyConfiguratorClass : IServicesConfigurator
    {
        public void Configure(IServiceCollection serviceCollection)
        {
            serviceCollection.AddScoped<OoyalaController>();
            serviceCollection.AddTransient<IOoyalaRepository, OoyalaComponentRepository>();
        }
    }
}

Register the configurator in your config like this:

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
    <sitecore>
        <services>
            <configurator type="MyProject.MyConfiguratorClass, MyProject" />
        </services>
    </sitecore>
</configuration>

That will enable the IoC Container to resolve the dependencies for the controller when it is created.

Check out this pose on Dependency Injection in Sitecore 8.2 by Kam - there are some more details there about how to register all controllers in your project in a single call to make it easier.

Answer 3

A quick fix could be to do this (using ServiceLocator as SXA does in the StandardController):

private readonly IOoyalaRepository _repository;
public OoyalaController()
{
    _repository = ServiceLocator.Current.Resolve<IOoyalaRepository>();
}

For now I have no answer to why the maps controller does work with a constructor with parameters...

Answer 4

The problem is that you don't have a parameterless constructor for your controller. It's not the component that is the issue. The code is expecting to be able to instantiate your controller without parameters, but because you defined a constructor for your controller that does have a parameter you now need to explicitly define a parameterless constructor, as well.

Changing your controller to the following help to highlight the issue by induction:

public class OoyalaController : StandardController
{
    private readonly IOoyalaRepository _repository;

    public OoyalaController(IOoyalaRepository repository)
    {
        _repository = repository;
    }

    public OoyalaController()
    {
       ...instantiate your Repository here, or resolve it or...
    }

    // as mentioned in comments, need to instantiate the Repository or this will fail
    protected override object GetModel()
    {
        return _repository.GetModel();
    }
}

To verify that this resolves your issue, try changing the parameterless constructor to the following temporarily:

    public OoyalaController()
    {
       _repository = new OoyalaRepository(); // replace with actual constructor, if different
    }

So long as the above works, we can verify that this controller was your issue. The next thing to do is fix your IoC issue.

As mentioned by @RichardSeal, you should not Service Locate (I previously used this as a DI example, even though Service Locator is not a(n) (anti-)pattern that I recommend for use), but rather you should be using IoC to register your controller, so that your code can instantiate it with parameters. I won't repeat his answer here, but the first thing that you should do is remove the new parameterless constructor from your controller and register the class per Richard or Alan's solution.

Answer 5

Just to summarize the discussion - you don't need to register controllers in the SXA container. Just like Alan mention above they will be automatically resolved by ExperienceAcceleratorDependencyResolver.

But please remember to register all of the services which you want to inject into your controller!

I would suggest usage of ServiceLocator just in the places where constructor injection isn't possible.

@Richard Seal: Thanks to SXA you are able to use Dependency Injection also on Sitecore 8.1! (we are using .NET Core container, just like in the 8.2)

Answer 6

I think the following statement will work out best for you:

_repository = ServiceLocator.Current.Resolve<ISimpleComponentRepository >();