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Encoding and decoding knowledge utilizing the Hummingbird framework

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Encoding and decoding knowledge utilizing the Hummingbird framework

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HTTP is all about sending and receiving knowledge over the community. Initially it was solely utilized to switch HTML paperwork, however these days we use HTTP to switch CSS, JavaScript, JSON and plenty of different knowledge varieties. In response to the requirements, the Content material-Kind and Content material-Size headers can be utilized to have a greater understanding concerning the knowledge contained in the physique of the HTTP request.

Fashionable internet servers can mechanically ship again these headers primarily based on the thing you come back in a request handler operate. That is the case with Hummingbird, it has built-in encoding and decoding help, which makes the information transformation course of actually easy.

For instance if we setup the next route handler and name the good day endpoint utilizing cURL with the -i flag, the output will include a bit extra details about the response. ℹ️

router.get("good day") { _ in "good day" }
        

There are some fundamental headers within the response, the content-type header comprises the kind of the physique, which is at present a plain textual content with an UTF-8 encoded string, since we have returned a String kind utilizing our Swift code. The content-length is 5, as a result of the character depend of good day is 5.

There are another headers, however ignore these, the fascinating half for us is the content-type header, and the way it’s injected into the response. Each Hummingbird software has an encoder and a decoder property. The default values for these are NullEncoder and NullDecoder. The encoders can magically add the correct content material kind header to the response and encode some object right into a HTTP response knowledge. Not the whole lot is response encodable and decodable by default, however you’ll be able to encode String objects in Hummingbird by default. 👍

Encoding and decoding JSON objects

Lots of the server-side Swift programs are used to create JSON-based RESTful API backends for cell frontends. Hummingbird might help you with this, because it has built-in encoding and decoding help for JSON objects by means of the Codable protocol.

First you must import the HummingbirdFoundation library, since it’s a standalone helper instrument constructed across the Basis framework, and that package deal comprises the Codable kind extensions. Subsequent you must setup the encoder and decoder utilizing a JSONEncoder and JSONDecoder occasion. After this, you’ll be able to simply remodel incoming HTTP physique objects into Swift knowledge buildings and return with them as nicely. Let me present you a fast instance. ⤵️

import Hummingbird
import HummingbirdFoundation

struct Foo: Codable {
    let bar: String
    let baz: Int
}

extension Foo: HBResponseCodable {}


extension HBApplication {

    func configure(_ args: AppArguments) throws {
        
        decoder = JSONDecoder()
        encoder = JSONEncoder()
        
        router.put up("foo") { req async throws -> Foo in
            guard let foo = strive? req.decode(as: Foo.self) else {
                throw HBHTTPError(.badRequest, message: "Invalid request physique.")
            }
            return foo
        }
    }

    
}

As you’ll be able to see the kind of the returned content material is now correctly set to software/json and the size can be supplied by default. We had been additionally in a position to decode the Foo object from the request physique and mechanically encode the thing after we returned with it.

Codable routing works like magic and these days it is a fairly normal strategy if it involves server-side Swift frameworks. Enjoyable reality: this strategy was initially ‘invented’ for Swift by the builders of the Kitura framework. Thanks. 🙏

The HBResponseCodable and the HBResponseEncodable protocols are the fundamental constructing blocks and the HBRequestDecoder and the HBResponseEncoder are accountable for this magic. They make it attainable to decode a Decodable object from a HBRequest and encode issues right into a HBResponse object and likewise present extra headers. If you need to know extra, I extremely suggest to check out the JSONCoding.swift file contained in the framework. 😉

Encoding and decoding HTML types

I do not wish to get an excessive amount of into the main points of constructing types utilizing HTML code, by the way in which there’s a higher manner utilizing SwiftHtml, however I would wish to focus extra on the underlying knowledge switch mechanism and the enctype attribute. There are 3 attainable, however solely two helpful values of the encoding kind:

  • software/x-www-form-urlencoded
  • multipart/form-data

URL encoding and decoding is supported out of the field when utilizing HummingbirdFoundation, this can be a easy wrapper across the URL encoding mechanism to simply help knowledge transformation.

decoder = URLEncodedFormDecoder()
encoder = URLEncodedFormEncoder()

In order that’s one option to course of a URL encoded kind, the opposite model relies on the multipart strategy, which has no built-in help in Hummingbird, however you should utilize the multipart-kit library from the Vapor framework to course of such types. You’ll find a working instance right here. I even have an article about the best way to add information utilizing multipart kind knowledge requests. So there are many sources on the market, that is why I will not embrace an instance on this article. 😅

Header primarily based encoding and decoding

First we have now to implement a customized request decoder and a response encoder. Within the decoder, we’ll verify the Content material-Kind header for a given request and decode the HTTP physique primarily based on that. The encoder will do the very same factor, however the response physique output goes to rely on the Settle for header area. Here is how one can implement it:

struct AppDecoder: HBRequestDecoder {
    
    func decode<T>(
        _ kind: T.Kind,
        from req: HBRequest
    ) throws -> T the place T: Decodable {
        swap req.headers["content-type"].first {
        case "software/json", "software/json; charset=utf-8":
            return strive JSONDecoder().decode(kind, from: req)
        case "software/x-www-form-urlencoded":
            return strive URLEncodedFormDecoder().decode(kind, from: req)
        default:
            throw HBHTTPError(.badRequest)
        }
    }
}

struct AppEncoder: HBResponseEncoder {

    func encode<T>(
        _ worth: T,
        from req: HBRequest
    ) throws -> HBResponse the place T: Encodable {
        swap req.headers["accept"].first {
        case "software/json":
            return strive JSONEncoder().encode(worth, from: req)
        case "software/x-www-form-urlencoded":
            return strive URLEncodedFormEncoder().encode(worth, from: req)
        default:
            throw HBHTTPError(.badRequest)
        }
    }
}

Now for those who change the configuration and use the AppEncoder & AppDecoder you must be capable of reply primarily based on the Settle for header and course of the enter primarily based on the Content material-Kind header.

import Hummingbird
import HummingbirdFoundation

struct Foo: Codable {
    let bar: String
    let baz: Int
}

extension Foo: HBResponseEncodable {}
extension Foo: HBResponseCodable {}

extension HBApplication {

    func configure(_ args: AppArguments) throws {
        
        decoder = AppDecoder()
        encoder = AppEncoder()
        
        router.put up("foo") { req async throws -> Foo in
            guard let foo = strive? req.decode(as: Foo.self) else {
                throw HBHTTPError(.badRequest, message: "Invalid request physique.")
            }
            return foo
        }
    }
}

Be at liberty to mess around with some cURL snippets… 👾

# ought to return JSON encoded knowledge
curl -i -X POST http://localhost:8080/foo 
    -H "Content material-Kind: software/x-www-form-urlencoded" 
    -H "Settle for: software/json" 
    --data-raw 'bar=bar&baz=42'

# ought to return URL encoded knowledge
curl -i -X POST http://localhost:8080/foo 
    -H "Content material-Kind: software/json" 
    -H "Settle for: software/x-www-form-urlencoded" 
    --data-raw '{"bar": "bar", "baz": 42}'

# ought to return with a 400 standing code
curl -i -X POST http://localhost:8080/foo 
    -H "Content material-Kind: software/json" 
    -H "Settle for: multipart/form-data" 
    --data-raw '{"bar": "bar", "baz": 42}'

So, primarily based on this text you must be capable of implement help to much more content material varieties by merely extending the app encoder and decoder. In fact you might need to import some extra package deal dependencies, however that is fantastic.

Uncooked requests and responses

Yet one more little factor, earlier than I finish this text: you’ll be able to entry the uncooked request physique knowledge and ship again a uncooked response utilizing the HBResponse object like this:

router.put up("foo") { req async throws -> HBResponse in
    
    if let buffer = req.physique.buffer {
        let rawInputData = buffer.getData(
            at: 0,
            size: buffer.readableBytes
        )
        print(rawInputData)
    }
    
    
    if let sequence = req.physique.stream?.sequence {
        for strive await chunk in sequence {
            print(chunk)
        }
    }
    
    guard let knowledge = "good day".knowledge(utilizing: .utf8) else {
        throw HBHTTPError(.internalServerError)
    }
    
    return .init(
        standing: .okay,
        headers: .init(),
        physique: .byteBuffer(.init(knowledge: knowledge))
    )
}

For smaller requests, you should utilize the req.physique.buffer property and switch it right into a Knowledge kind if wanted. Hummingbird has nice help for the brand new Swift Concurreny API, so you should utilize the sequence on the physique stream for those who want chunked reads. Now just one query left:

What varieties ought to I help?

The reply is easy: it relies upon. Like actually. These days I began to ditch multipart encoding and I desire to speak with my API utilizing REST (JSON) and add information as uncooked HTTP physique. I by no means actually needed to help URL encoding, as a result of for those who submit HTML types, you will finally face the necessity of file add and that will not work with URL encoded types, however solely with multipart.

In conclusion I would say that the excellent news is that we have now loads of alternatives and if you wish to present help for many of those varieties you do not have to reinvent the wheel in any respect. The multipart-kit library is constructed into Vapor 4, however that is one of many causes I began to love Hummingbird a bit extra, as a result of I can solely embrace what I really want. Anyway, competitors is an effective factor to have on this case, as a result of hopefully each frameworks will evolve for good… 🙃

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