Figure is a elegant declarative UI library, utilizing the Typed Tagless Final solution to the expression problem.

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• Deployment target iOS 10.0+
• Swift 4+
• Xcode 10+

A view is declared simply by:

let view: iOSRenderer = .view()

You can then render that view like so:

let renderedView: UIView = view.describe.view

You can simply create a var in your UIViewController as your root view, like so:

import FigureiOS

final class ViewController: UIViewController {

    // MARK: - View 

    var rootView: iOSRenderer {
        return .view()
    }
    
    // MARK: - Init
    
    // ...
    
    // MARK: - Lifecycle 
    
    override func loadView() {
        self.view = self.rootView.describe.view
    }

}

Notice we declaratively create the view in rootView and then render it by calling rootView.describe.view in loadView(). Alternatively you can subclass your UIViewController with RenderViewController and override the rootView property. RenderViewController handles your view rendering automatically, so even less boilerplate to write.

import FigureiOS

final class ViewController: RenderViewController {

    // MARK: - View 

    override var rootView: iOSRenderer {
        return .view()
    }
    
}

Declare view hierarchies like so:

let myNestedView: iOSRenderer = .view(
    config: [.backgroundColor(.red)],
    .view(
        layout: [.set(width: 100.0, height: 100.0)],
        .view(layout: [.fill]),
        .view(),
        .view()
    )
)

let view: UIView = myNestedView.describe.view

The above will create a root view which has a red background with 1 subview which has a width of 100.0 and a height of 100.0 which itself should have 3 subviews where 1 of those subviews fills the frame of it's parent view.

Figure allows you to use your custom views in case you want more flexibility. Simply use them by:

import FigureiOS

final class MyCustomView: UIView {}

let myCustomView: iOSRenderer = .view(of: MyCustomView.self)

let _myCustomView: UIView = myCustomView.describe.view

let myCustomNestedView: iOSRenderer = .view(
    of: MyCustomView.self,
    .view(
        .view(),
        .view(
            of: MyCustomView.self,
            config: [.backgroundColor(.red)]
        )
    )
)

let _myCustomNestedView: UIView = myCustomNestedView.describe.view

This library adheres to be as composable as possible, meaning it should be easy for someone to:

• Add a new type
• Add a new interpretation or operation

This example is shown by the FigureSerializable module. We've implemented a new target and added new functionality to our ViewDescriptor. If someone wanted to now make our view hierarchy codable you can easily do so now via:

import FigureSerializable

let view: iOSRenderer = .view()
guard 
    let json = view.describe.json
    else { return }
// use json...

Notice we are importing a new module FigureSerializable. Here is the rendered JSON:

Figure welcomes both fixes, improvements, and feature additions. If you'd like to contribute, open a pull request with a detailed description of your changes.

As a rule of thumb, if you're proposing an API breaking change or a change to existing functionality, consider proposing it by opening an issue, rather than a pull request; we'll use the issue as a public forum for discussing whether the proposal makes sense or not.

Haider Khan

• https://github.com/ZkHaider

Timothy Kautz

• https://github.com/littleowl