Code improvement - how to serve use pictures in Vapor?-CodePudding

I have a working directory that contains every user's picture and I am trying to implement a call that returns data containing the user's picture, defined in this structure:

struct ImageData: Content {
    var picture: Data // UIImage data
}

I tried to implement a solution also partially using what I found in the book 'Server Side Swift with Vapor' (version 3) in chapter 26 but that's different for me because I am not using Leaf and I need to return the data directly.

I came up with this function to return the user picture, which does its job but I am trying to improve it.

func getProfilePictureHandler(_ req: Request) throws -> EventLoopFuture<ImageData> {
    return User.find(req.parameters.get("userID"), on: req.db)
        .unwrap(or: Abort(.notFound))
        .flatMap { user in
            // To do: throw error (flatMapThrowing?)
            let filename = user.profilePicture!
            
            let path = req.application.directory.workingDirectory
                  imageFolder
                  filename
            
            // Improvement: Do I need this?
            var data = Data()
            
            return req.fileio.readFile(at: path) { buffer -> EventLoopFuture<Void> in
                let additionalData = Data(buffer: buffer)
                data.append(contentsOf: additionalData)
                return req.eventLoop.makeSucceededVoidFuture()
            }.map {
                return ImageData(picture: data)
            }
        }
}

First:

How to implement this using flatMapThrowing? If I replace flatMap with flatMapThrowing I get this error: "Cannot convert return expression of type 'EventLoopFuture' to return type 'ImageData'". Which doesn't make sense to me considering that flatMap allows returning a future and not a value.
I didn't find any solution other than using a Data variable and appending chunks of data as more data is read. I am not sure that this is thread-safe, FIFO and I don't consider it an elegant solution. Does anybody know any better way of doing it?

CodePudding user response：

The short answer is that as soon as you have the file path, Vapor can handle it all for you:

func getProfilePictureHandler(_ req: Request) throws -> EventLoopFuture<Response> {
    return User.find(req.parameters.get("userID"), on: req.db)
        .unwrap(or: Abort(.notFound))
        .tryflatMap { user in
            // To do: throw error (flatMapThrowing?)
            guard let filename = user.profilePicture else {
                throw Abort(.notFound)
            }
            
            let path = req.application.directory.workingDirectory
                  imageFolder
                  filename
            
            return req.fileio.streamFile(at: path)
        }
}

You can use tryFlatMap to have a flatMap that can throw and you want to return a Response. Manually messing around with Data is not usually a good idea.

However, the better answers are use async/await and the FileMiddleware as two tools to clean up your code and remove the handler altogether