Inherit http verb attributes from abstract REST controller

Question

I am trying to implement a base REST controller in aspnetcore 1.0.1 (kind of inspired from NancyFx) and it feels like this should be something that can be achieved with such a composable framework, however, I just cant get it right. The google foo is clearly weak with me today!

I have the following base controller (obviously not fully implemented yet)...

[Route("api/[controller]")]
public abstract class RestApiController<T> : Controller
{
    protected abstract Func<int, Task<T>> Get { get; }
    protected abstract Func<Task<IEnumerable<T>>> List { get; }

    [HttpGet()]
    protected virtual async Task<IEnumerable<T>> OnList()
    {
        if (this.List == null)
        {
            this.NotFound();
        }

        return await this.List.Invoke();
    }

    [HttpGet("{id:int}")]
    protected virtual async Task<T> OnGet(int id)
    {
        if (this.Get == null)
        {
            this.NotFound();
        }

        return await this.Get.Invoke(id);
    }
}

Which is inherited by the actual controller doing the work...

public class ArticleSummariesController : RestApiController<ArticleExtension>
{
    private readonly ArticleManager articleManager;

    protected override Func<int, Task<ArticleExtension>> Get => null;
    protected override Func<Task<IEnumerable<ArticleExtension>>> List => this.ListAll;

    public ArticleSummariesController(ArticleManager articleManager)
    {
        this.articleManager = articleManager;
    }

    private async Task<IEnumerable<ArticleExtension>> ListAll()
    {
        return await this.articleManager.GetAllAsync();
    }

}

The idea is that the base controller will be responsible for handling the actual requests but delegate responsibility to it's children to provide and manipulate the data. This is so that we can ensure REST conformance in the requests but loosely couple domain logic from the controllers into "managers" that act as a facade and take repositories and apply business logic.

The problem with the code so far is that the HttpGet() attributes on the base class do not produce routes for the child class. The controller route attribute on the base class is inherited though (as stated in the docs).

David Pine · Accepted Answer · 2016-10-05 18:02:26Z

0

I could be wrong, but I immediately assume that you need a RouteAttribute on either the base class or the subclass. For example:

[Route("api/[controller]")]
public abstract class RestApiController<T> : Controller
{
    protected abstract Func<int, Task<T>> Get { get; }
    protected abstract Func<Task<IEnumerable<T>>> List { get; }

    [HttpGet, Route("list")]
    protected virtual async Task<IEnumerable<T>> OnList()
    {
        if (this.List == null)
        {
            this.NotFound();
        }

        return await this.List.Invoke();
    }

    [HttpGet, Route("get/{id:int}")]
    protected virtual async Task<T> OnGet(int id)
    {
        if (this.Get == null)
        {
            this.NotFound();
        }

        return await this.Get.Invoke(id);
    }
}

answered Oct 5, 2016 at 18:02

David Pine

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1 Comment

Rich Andrews Over a year ago

The problem with the route attribute is I will lose the REST like urls. E.g. GET api/articlesummaries as opposed to api/arriclesummaries/list. Whilst the route attributes do inherit the http verb attributes do not

Rich Andrews · Accepted Answer · 2016-10-06 08:21:09Z

Yet again, the answer was staring me in the face! I had the parent methods declared as protected not public so they were not considered eligible actions!

After reading more about the ApplicationModel here it all became clear...

ActionModel – represents an action of a controller. An instance of this class is created for each eligible action on a controller. There are multiple requirements for a method to become an action, such as being public, non-abstract and not inherited from object.

So the modified code below works...

[Route("api/[controller]")]
public abstract class RestApiController<T> : Controller
{
    protected abstract Func<int, Task<T>> Get { get; }
    protected abstract Func<Task<IEnumerable<T>>> List { get; }

    [HttpGet()]
    public virtual async Task<IEnumerable<T>> OnList()
    {
        if (this.List == null)
        {
            this.NotFound();
        }

        return await this.List.Invoke();
    }

    [HttpGet("{id:int}")]
    public virtual async Task<T> OnGet(int id)
    {
        if (this.Get == null)
        {
            this.NotFound();
        }

        return await this.Get.Invoke(id);
    }
}

public class ArticleSummariesController : RestApiController<ArticleExtension>
{
    private readonly ArticleManager articleManager;

    protected override Func<int, Task<ArticleExtension>> Get => null;
    protected override Func<Task<IEnumerable<ArticleExtension>>> List => this.ListAll;

    public ArticleSummariesController(ArticleManager articleManager)
    {
        this.articleManager = articleManager;
    }

    private async Task<IEnumerable<ArticleExtension>> ListAll()
    {
        return await this.articleManager.GetAllAsync();
    }

}

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