How to handle multipart request with Vapor 3

Question

I'm a vapor beginner and I chose to start with Vapor 3-rc because it seems to break change from Vaport 2. Unfortunately, there isn't a complete documentation for now.

I'm currently trying to upload a simple txt file from Postman to my Vapor 3 local server.

Here's my route

let uploadController = FileUploadController()
router.post("uploadtxt", use: uploadController.uploadTXT)

and my controller

final class FileUploadController {
    func uploadTXT(_ req: Request) throws -> Future<String> {
        return try req.content.decode(MultipartForm.self).map(to: String.self, { form in
            let file = try form.getFile(named: "txtfile")
            return file.filename ?? "no-file"
        })
    }
}

First, by executing the Postman request, the server returns:

{"error":true,"reason":"There is no configured decoder for multipart\/form-data; boundary=...}

By investigating the source code and the limited documentation on this, it seems that I should declare a decoder to support multipart incoming requests.

So I did:

var contentConfig = ContentConfig.default()
let decoder = FormURLDecoder()
contentConfig.use(decoder: decoder, for: .multipart)
services.register(contentConfig)

I used FormURLDecoder because it seemed to be the closest class for my needs IMO, implementing BodyDecoder

Now it infite-loops into func decode<T>(_ type: T.Type) throws -> T where T: Decodable of FormURLSingleValueDecoder , and I'm stuck here with very few web resource.

Answer 1

I ended on the Vapor slack, which is a good place to find some info & a bit of help.

The solution is quite simple. Instead of using req.content.decode(MultipartForm.self) , prefer use MultipartForm.decode(from: req) :

final class FileUploadController {
    func uploadTXT(_ req: Request) throws -> Future<String> {
        return try MultipartForm.decode(from: req).map(to: String.self, { form in
            let file = try form.getFile(named: "txtfile")
            return file.filename ?? "no-file"
        })
    }
}

And forget the service registering part of my question.