Swift Declarative Configuration

Swift Declarative Configuration (SDC, for short) is a tiny library, that enables you to configure your objects in a declarative, consistent and understandable way, with ergonomics in mind. It can be used to configure any objects on any platform, including server-side-swift.

Products

• FunctionalModification

  Provides modification functions for copying and modifying immutable stuff. It is useful for self-configuring objects like builder, when modifying methods should return modified self.

• FunctionalKeyPath

  Functional KeyPath wrapper.

• FunctionalConfigurator

  Functional configurator for anything, enables you to specify modification of an object and to apply the modification later.

  Also contains self-implementing protocols (ConfigInitializable, CustomConfigurable) to enable you add custom configuration support for your types (NSObject already conforms to it for you).

• FunctionalBuilder

  Functional builder for anything, enables you to modify object instances in a declarative way. Also contains BuilderProvider protocol with a computed builder property and implements that protocol on NSObject type.

• FunctionalClosures

  Functional closures allow you to setup functional handlers & datasources, the API may seem a bit strange at the first look, so feel free to ask or discuss anything here.

• DeclarativeConfiguration

  Wraps and exports all the products.

Basic Usage

See tests for more

No SDC

class ImageViewController: UIViewController {
  let imageView: UIImageView = {
    let imageView = UIImageView()
    imageView.contentMode = .scaleAspectFit
    imageView.backgroundColor = .black
    imageView.layer.masksToBounds = true
    imageView.layer.cornerRadius = 10
    return imageView
  }()
    
  override func loadView() {
    self.view = imageView
  }
}

FunctionalConfigurator

Note: This way is recommended, but remember, that custom types MUST implement initializer with no parameters even if the superclass already has it or you will get a crash otherwise.

import FunctionalConfigurator

class ImageViewController: UIViewController {
  let imageView = UIImageView { $0 
    .contentMode(.scaleAspectFit)
    .backgroundColor(.black)
    .layer.scope { $0
      .masksToBounds(true)
      .cornerRadius(10)
    }
  }
    
  override func loadView() {
    self.view = imageView
  }
}

FunctionalBuilder

Note: This way is recommended too, and it is more safe, because it modifies existing objects.

import FunctionalBuilder

class ImageViewController: UIViewController {
  let imageView = UIImageView().builder
    .contentMode(.scaleAspectFit)
    .backgroundColor(.black)
    .layer.masksToBounds(true)
    .layer.cornerRadius(10)
    .build()
    
  override func loadView() {
    self.view = imageView
  }
}

FunctionalClosures

No SDC

Declaration

public class TapGestureRecognizer: UITapGestureRecognizer {
  var onTapGesture: ((TapGestureRecognizer) -> Void)?
    
  init() {
    super.init(target: nil, action: nil)
    commonInit()
  }
    
  override public init(target: Any?, action: Selector?) {
    super.init(target: target, action: action)
    commonInit()
  }
    
  private func commonInit() {
    self.addTarget(self, action: #selector(handleTap))
  }
    
  @objc private func handleTap(_ recognizer: TapGestureRecognizer) {
    onTapGesture?(recognizer)
  }
}

Usage

let tapRecognizer = TapGestureRecognizer()

// handler setup
tapRecognizer.onTapGesture = { recognizer in
    // ...
}

// call from the outside
tapRecognizer.onTapGesture?(tapRecognizer)

With SDC

Declaration

public class TapGestureRecognizer: UITapGestureRecognizer {
  @Handler<TapGestureRecognizer>
  var onTapGesture
    
  init() {
    super.init(target: nil, action: nil)
    commonInit()
  }
    
  override public init(target: Any?, action: Selector?) {
    super.init(target: target, action: action)
    commonInit()
  }
    
  private func commonInit() {
    self.addTarget(self, action: #selector(handleTap))
  }
    
  @objc private func handleTap(_ recognizer: TapGestureRecognizer) {
    _onTapGesture(recognizer)
  }
}

Usage

let tapRecognizer = TapGestureRecognizer()

// handler setup now called as function
tapRecognizer.onTapGesture { recognizer in
    // ...
}

// call from the outside now uses propertyWrapper projectedValue API, which is not as straitforward
// and it is nice, because:
// - handlers usually should not be called from the outside
// - you do not lose the ability to call it, but an API tells you that it's kinda private
tapRecognizer.$onTapGesture?(tapRecognizer)

Also you can create such an instance with Configurator:

let tapRecognizer = TapGestureRecognizer { $0 
  .$onTapGesture { recognizer in 
    // ...
  }
}

More

Builder

Customize any object by passing initial value to a builder

let object = Builder(Object())
  .property.subproperty(value)
  .build() // Returns modified object

For classes you can avoid returning a value by calling apply method, instead of build

let _class = _Class()
Builder(_class)
  .property.subproperty(value)
  .apply() // Returns Void

In both Builders and Configurators you can use scoping

let object = Object { $0
  .property.subproperty(value)
}

Conform your own types to BuilderProvider protocol to access builder property.

import CoreLocation
import DeclarativeConfiguration

extension CLLocationCoordinate2D: BuilderProvider {}
// Now you can access `location.builder.latitude(0).build()`

Configurator

Note: Your NSObject classes must implement init() to use Configurators. It’s a little trade-off for the convenience it brings to your codebase, see tests for an example.

DataSource

OptionalDataSource and DataSource types are very similar to the Handler, but if Handler<Input> is kinda OptionalDataSource<Input, Void>, the second one may have different types of an output. Usage is similar, different types are provided just for better semantics.

Installation

Basic

You can add DeclarativeConfiguration to an Xcode project by adding it as a package dependency.

1. From the File menu, select Swift Packages › Add Package Dependency…
2. Enter "https://github.com/makeupstudio/swift-declarative-configuration" into the package repository URL text field
3. Choose products you need to link them to your project.

Recommended

If you use SwiftPM for your project structure, add DeclarativeConfiguration to your package file.

.package(
  url: "git@github.com:capturecontext/swift-declarative-configuration.git", 
  .upToNextMinor(from: "0.3.0")
)

or via HTTPS

.package(
  url: "https://github.com:capturecontext/swift-declarative-configuration.git", 
  .exact("0.3.0")
)

Do not forget about target dependencies:

.product(
    name: "DeclarativeConfiguration", 
    package: "swift-declarative-configuration"
)

License

This library is released under the MIT license. See LICENSE for details.