Having issues implementing calling this interface

Question

Can't seem to wrap my head around using an interface sometimes and am stuck trying to call this. Sorry, I realize this should be simple, but the examples I am finding just aren't working.

I have:

namespace ApiConnection{
    public interface IRestApiCalls{
        Task<bool> Login(string userName, string password);
    }
}

And it's implementation

namespace ApiConnection{
    class TestRestApiService : IRestApiCalls    {
        public async Task<bool> Login(string userName, string password){
            //Do whatever
        }
    }
}

How would I call Login? I have something similar to:

namespace Bll{
    public class Bll : IBll{  //yes, I can call this interface no problem
        public Login(string userName, string password){
            //What goes here to call the IRestApiCalls.Login interface?
        }
    }
}

Answer 1

You do not call an interface. An interface simply defines a contract which your class must adhere to.

You would call the method just like any other:

var myService = new TestRestApiService();
myService.Login("rob", "hunter2");

However, since it's an interface, you can also write something like this:

public void LoginService(IRestApiCalls service)
{
    service.Login("rob", "hunter2");
}

Which means you don't care what class you're given, as long as they adhere to the the contract laid out in the interface IRestApiCall

Answer 2

Assuming that you cannot make your login method async , you could use WaitAndUnwrapException :

IRestApiCalls rest = ...
var task = rest.Login(userName, password);
var result = task.WaitAndUnwrapException();
if (!result) {
    // Login has failed
}

If you have an option of making your own Login method async , you could await the Login from the REST object instead:

IRestApiCalls rest = ...
var result = await rest.Login(userName, password).ConfigureAwait(false);
if (!result) {
    // Login has failed
}