Alamofire doesn't catch error

Question

I'm using Alamofire to get data from my server. However, it doesn't catch the error, as the error returned is nil. I've tested with AFNetworking, and it works fine. For both operation, the status code returned is 401 Unauthorized . Is there's something with my code?

I'm using GrapeAPI for my backend. All it does is just to return the error on fail request

GrapeAPI

error!('Unauthorized', 401)

AFNetworking

manager.GET("someUrl", parameters: nil, success: { (_, object) in

        }, failure: { (operation, error) in
            // These are the outputs. I'm not assigning any values
            // error.localizedDescription = "Request failed: unauthorized (401)"
            // statusCode = 401
        })

Alamofire

Alamofire.request(.GET, "url", parameters: nil)
        .response { (a,b,data,error) in
        // These are the outputs. I'm not assigning any values
        // error = nil
        // data = {"error":"Unauthorized"}
        // statusCode = 401
        }

I can check the failure using the statusCode. But I prefer to check the error object instead. However, since the error is nil in Alamofire, it's quite confusing to check whether the request has failed or not.

Answer 1

As Matt has mentioned in the comment, I need to add .validate() before calling .response(). This is by design. Final code as below:

Alamofire.request(.GET, "url", parameters: nil)
    .validate()
    .response { (a,b,data,error) in
    // error won't be nil now
    // and statusCode will be 401
    }

Read this detailed explanation(thanks!) for more information.