Tips on how to write HTML in Swift?

Introducing SwiftHtml

This time we will begin all the things from scratch. Within the first part of this text I’ll present you the best way to setup the SwiftHtml as a package deal dependency and the best way to generate HTML output primarily based on a template file. Let’s begin by making a model new executable Swift package deal.

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

You may as well begin with a macOS Command Line Instrument from Xcode if you want, however these days I choose Swift Packages. Anyway, we should always add SwiftHtml as a dependency to our package deal instantly.

import PackageDescription

let package deal = 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 very primary instance to get to know with SwiftHtml. Within the important.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("Howdy, World!")
            
            Meta().charset("utf-8")
            Meta().identify(.viewport).content material("width=device-width, initial-scale=1")
        }
        Physique {
            Essential {
                Div {
                    H1("Howdy, 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 comply with the naming conventions as intently as potential, so in the event you’ve written HTML earlier than this syntax ought 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 an alternative of us.

Since we’re utilizing a website particular language in Swift, the compiler can type-check all the things at build-time, this manner it is 100% certain that our HTML code will not have syntax points. In fact you possibly can nonetheless make semantic errors, however that is additionally potential in the event you’re not utilizing a DSL. 😅

The primary benefit right here is that you just will not be capable of 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 potential 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 potential to create all kinds of SGML-based doc sorts, as a result of the SwiftHtml package deal comes with an abstraction layer. When you check out the package deal construction you need to see that contained in the Sources listing there are a number of different directories, the core of the package deal is the SwiftSgml element, which permits builders to create different area particular languages on high of the bottom parts. 🤔

For instance, in the event you check out the SwiftRss package deal you will note that it is a easy extension over the SwiftSgml library. You possibly can subclass the Tag object to create a brand new (area particular) tag with an underlying Node object to symbolize a customized merchandise in 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 liable for rendering the doctype declaration earlier than the foundation tag if wanted, additionally in fact the doc comprises the foundation tag, which is the start of all the things. 😅

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 type.

So the SwiftHtml package deal is only a set of HTML guidelines on high of the SwiftSgml library and it follows the W3C HTML reference guides. You should use the output string to save lots of a HTML file, this manner you possibly can generate static web sites through the use of the SwiftHtml library.

import Basis
import SwiftHtml

let doc = Doc(.html) {
    Html {
        Head {
            Title("Howdy, World!")
            
            Meta().charset("utf-8")
            Meta().identify(.viewport).content material("width=device-width, initial-scale=1")
        }
        Physique {
            Essential {
                Div {
                    H1("Howdy, 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 method to make use of SwiftHtml, for my part static web site turbines are positive, however the actual 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 neighborhood additionally created a type-safe HTML DSL library referred to as HTMLKit, so why create one thing very comparable?

Properly, I attempted all of the out there Swift HTML DSL libraries that I used to be capable of finding on GitHub, however I used to be not completely happy with the at present out there options. Lots of them was outdated, incomplete or I merely did not like the flavour of the DSL. I needed 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? Properly, it is fairly easy, let’s add Vapor as a dependency to our mission first.

import PackageDescription

let package deal = 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 symbolize a template file, so let’s name it TemplateRepresentable.

import Vapor
import SwiftSgml

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

Subsequent, we want one thing that may render a template file and return with a Response object, that we are able to use inside a request handler after we setup the route handlers in Vapor. Since we will return a HTML string, it’s essential to set the right 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 want it.

import Vapor

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

Now we simply should create a HTML template file. I am often 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 proud of 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 {
                Essential {
                    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 net 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 Setting.detect()
strive LoggingSystem.bootstrap(from: &env)
let app = Software(env)
defer { app.shutdown() }

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

strive app.run()

Kind of that is it, you need to be capable of run the server and hopefully you need to see the rendered HTML doc in the event you open the localhost:8080 deal with utilizing your browser.

Additionally it is potential to make use of one template inside one other, since you possibly can name the render technique on a template and that template will return a Tag. The great thing about this method is that you may compose smaller templates collectively, this manner you possibly can provide you with a pleasant mission construction with reusable HTML templates written completely in Swift. I am more than pleased with this straightforward answer and looks like, for me, there is no such thing as a turning again to Leaf or Tau… 🤓