How you can write HTML in Swift?

Introducing SwiftHtml

This time we’ll begin every part from scratch. Within the first part of this text I’ll present you easy methods to setup the SwiftHtml as a bundle dependency and easy methods to generate HTML output primarily based on a template file. Let’s begin by making a model new executable Swift bundle.

mkdir Instance
cd "$_"
swift bundle init --type=executable
open Package deal.swift

You may also begin with a macOS Command Line Device from Xcode if you want, however these days I desire Swift Packages. Anyway, we should always add SwiftHtml as a dependency to our bundle straight away.

import PackageDescription

let bundle = Package deal(
    identify: "Instance",
    platforms: [
        .macOS(.v12)
    ],
    dependencies: [
        .package(url: "https://github.com/binarybirds/swift-html", from: "1.2.0"),
    ],
    targets: [
        .executableTarget(name: "Example", dependencies: [
            .product(name: "SwiftHtml", package: "swift-html"),
        ]),
        .testTarget(identify: "ExampleTests", dependencies: ["Example"]),
    ]
)

All proper, now we’re prepared to jot down some Swift DSL code. We’ll begin with a extremely fundamental instance to get to know with SwiftHtml. Within the foremost.swift file we should always create a brand new HTML doc, then we are able to use SwiftHtml’s built-in renderer to print the html supply. 🖨

import SwiftHtml

let doc = Doc(.html) {
    Html {
        Head {
            Title("Good day, World!")
            
            Meta().charset("utf-8")
            Meta().identify(.viewport).content material("width=device-width, initial-scale=1")
        }
        Physique {
            Predominant {
                Div {
                    H1("Good day, World!")
                    P("This web page was generated by the SwiftHtml library.")
                }
            }
            .class("container")
        }
    }
}

let html = DocumentRenderer(minify: false, indent: 2).render(doc)
print(html)

As you possibly can see the code is fairly simple, particularly if a bit about HTML. The SwiftHtml library tries to observe the naming conventions as carefully as doable, so if you happen to’ve written HTML earlier than this syntax needs to be very acquainted, besides that you do not have to jot down opening and shutting tags, however we are able to make the most of the Swift compiler to do the boring repetative duties as a substitute of us.

Since we’re utilizing a site particular language in Swift, the compiler can type-check every part at build-time, this manner it is 100% certain that our HTML code will not have syntax points. After all you possibly can nonetheless make semantic errors, however that is additionally doable if you happen to’re not utilizing a DSL. 😅

The principle benefit right here is that you just will not have the ability to mistype or misspell tags, and you do not even have to consider closing tags, however you should use end result builders to assemble the HTML node tree. SwiftHtml makes use of tags and it will construct a tree from them, this manner it’s doable to effectively render all the construction with correct indentation or minification whether it is wanted.

The DocumentRenderer object can render a doc, it’s also doable to create all kinds of SGML-based doc varieties, as a result of the SwiftHtml bundle comes with an abstraction layer. If you happen to check out the bundle construction it is best to see that contained in the Sources listing there are a number of different directories, the core of the bundle is the SwiftSgml element, which permits builders to create different area particular languages on prime of the bottom parts. 🤔

For instance, if you happen to check out the SwiftRss bundle you will note that it is a easy extension over the SwiftSgml library. You’ll be able to subclass the Tag object to create a brand new (area particular) tag with an underlying Node object to signify a customized merchandise to your doc.

The SwiftSgml library may be very light-weight. The Node struct is a illustration of a given SGML node with a customized sort, identify and attributes. The Tag class is all about constructing a hierarchy in between the nodes. The Doc struct is a particular object which is accountable for rendering the doctype declaration earlier than the foundation tag if wanted, additionally after all the doc comprises the foundation tag, which is the start of every part. 😅

SwiftSgml additionally comprises the DocumentRenderer and a easy TagBuilder enum, which is a end result builder and it permits us to outline our construction in a SwiftUI-like fashion.

So the SwiftHtml bundle is only a set of HTML guidelines on prime of the SwiftSgml library and it follows the W3C HTML reference guides. You need to use the output string to save lots of a HTML file, this manner you possibly can generate static web sites by utilizing the SwiftHtml library.

import Basis
import SwiftHtml

let doc = Doc(.html) {
    Html {
        Head {
            Title("Good day, World!")
            
            Meta().charset("utf-8")
            Meta().identify(.viewport).content material("width=device-width, initial-scale=1")
        }
        Physique {
            Predominant {
                Div {
                    H1("Good day, World!")
                    P("This web page was generated by the SwiftHtml library.")
                }
            }
            .class("container")
        }
    }
}

do {
    let dir = FileManager.default.homeDirectoryForCurrentUser
    let file = dir.appendingPathComponent("index.html")
    let html = DocumentRenderer(minify: false, indent: 2).render(doc)
    strive html.write(to: file, atomically: true, encoding: .utf8)
}
catch {
    fatalError(error.localizedDescription)
}

This is only one means to make use of SwiftHtml, for my part static web site turbines are wonderful, however the true enjoyable begins when you possibly can render web sites primarily based on some sort of dynamic information. 🙃

Utilizing SwiftHtml with Vapor

Vapor has an official template engine referred to as Leaf plus the group additionally created a type-safe HTML DSL library referred to as HTMLKit, so why create one thing very related?

Effectively, I attempted all of the accessible Swift HTML DSL libraries that I used to be capable of finding on GitHub, however I used to be not solely glad with the at present accessible options. Lots of them was outdated, incomplete or I merely did not like the flavour of the DSL. I wished to have a library which is freakin’ light-weight and follows the requirements, that is the explanation why I’ve constructed SwiftHtml. 🤐

How can we combine SwiftHtml with Vapor? Effectively, it is fairly easy, let’s add Vapor as a dependency to our undertaking first.

import PackageDescription

let bundle = Package deal(
    identify: "Instance",
    platforms: [
        .macOS(.v12)
    ],
    dependencies: [
        .package(url: "https://github.com/binarybirds/swift-html", from: "1.2.0"),
        .package(url: "https://github.com/vapor/vapor", from: "4.54.0"),
    ],
    targets: [
        .executableTarget(name: "Example", dependencies: [
            .product(name: "SwiftHtml", package: "swift-html"),
            .product(name: "Vapor", package: "vapor"),
        ]),
        .testTarget(identify: "ExampleTests", dependencies: ["Example"]),
    ]
)

We’ll want a brand new protocol, which we are able to use assemble a Tag, that is going to signify a template file, so let’s name it TemplateRepresentable.

import Vapor
import SwiftSgml

public protocol TemplateRepresentable {
    
    @TagBuilder
    func render(_ req: Request) -> Tag
}

Subsequent, we’d like one thing that may render a template file and return with a Response object, that we are able to use inside a request handler once we setup the route handlers in Vapor. Since we’ll return a HTML string, it’s essential to set the correct response headers too.

import Vapor
import SwiftHtml

public struct TemplateRenderer {
    
    var req: Request
    
    init(_ req: Request) {
        self.req = req
    }

    public func renderHtml(_ template: TemplateRepresentable, minify: Bool = false, indent: Int = 4) -> Response {
        let doc = Doc(.html) { template.render(req) }
        let physique = DocumentRenderer(minify: minify, indent: indent).render(doc)
        return Response(standing: .okay, headers: ["content-type": "text/html"], physique: .init(string: physique))
    }
}

Lastly we are able to lengthen the built-in Request object to return a brand new template renderer if we’d like it.

import Vapor

public extension Request {
    var templates: TemplateRenderer { .init(self) }
}

Now we simply must create a HTML template file. I am normally making a context object proper subsequent to the template this manner I am going to have the ability to cross round contextual variables for every template file. I am fairly pleased with this method to this point. ☺️

import Vapor
import SwiftHtml


struct IndexContext {
    let title: String
    let message: String
}

struct IndexTemplate: TemplateRepresentable {
    
    let context: IndexContext
    
    init(_ context: IndexContext) {
        self.context = context
    }
    
    func render(_ req: Request) -> Tag {
        Html {
            Head {
                Title(context.title)
                
                Meta().charset("utf-8")
                Meta().identify(.viewport).content material("width=device-width, initial-scale=1")
            }
            Physique {
                Predominant {
                    Div {
                        H1(context.title)
                        P(context.message)
                    }
                }
                .class("container")
            }
        }
    }
}

Lastly we simply have to jot down some boilerplate code to start out up our Vapor internet server, we are able to use the app occasion and set a get request handler and render our template utilizing the newly created template renderer extension on the Request object.

import Vapor
import SwiftHtml

var env = strive Surroundings.detect()
strive LoggingSystem.bootstrap(from: &env)
let app = Utility(env)
defer { app.shutdown() }

app.get { req -> Response in
    let template = IndexTemplate(.init(title: "Good day, World!",
                                    message: "This web page was generated by the SwiftHtml library."))
    
    return req.templates.renderHtml(template)
}

strive app.run()

Kind of that is it, it is best to have the ability to run the server and hopefully it is best to see the rendered HTML doc if you happen to open the localhost:8080 handle utilizing your browser.

It is usually doable to make use of one template inside one other, since you possibly can name the render methodology on a template and that template will return a Tag. The great thing about this method is that you could compose smaller templates collectively, this manner you possibly can give you a pleasant undertaking construction with reusable HTML templates written solely in Swift. I am more than pleased with this straightforward resolution and looks as if, for me, there is no such thing as a turning again to Leaf or Tau… 🤓