DeclarativeLayoutKit

Declarative and type-safe framework for fast UI layout

Overview

• Requirements
• Usage
• How this framework differs from the others?
• Installation
• Credits
• License

Requirements

• iOS 11.0
• Xcode 12.5
• Swift 5.4

Usage

🚀 Property chaining

Absolutely all mutable properties are represented in the function using code generation powered by Sourcery.

let myLabel = UILabel()
    .numberOfLines(0)
    .text("Hello buddy")
    .backgroundColor(.blue)
    .isHighlighted(true)
    .borderWidth(1)
    .borderColor(.cyan)

Currently, property chaining is supported in the following types: UIView, UIControl, UILabel, UIImageView, UIScrollView, UITextView, UITableView, UICollectionView, UITextField, UIButton, UISlider, UISwitch, UIStackView.

You can also easily generate functions for other types – see how

😋 And some extra syntactic sugar:

Assignable to variable:

class ViewController: UIViewController {
    weak var myLabel: UILabel!

    override func loadView() {
        ...

        view.addSubview(
            UILabel()
                .numberOfLines(0)
                .text("Voila")
                // sets a reference of object that calls function(in this case, created UILabel instance) to passed variable
                .assign(to: &myLabel)
        )

        ...
    }
}

Closure based actions and gestures:

UIControl()
    .addAction(for: .valueChanged, { print("value changed") })

UIButton()
    .title("Tap me")
    .onTap({ print("didTap") }) // wrap .addAction(for: .touchUpInside, { .. })

UIView()
    .onTapGesture({ print("Kek") })
    .onLongTapGesture({ print("Cheburek") })

// ⚠️ Don't forget about ARC when use some parent view in action closure, to prevent retain cycle

👨‍👨‍👦‍👦 UIStackView extra_most_usefull helpers

Preconfigured stack initializer:

HorizontalStack([...]) // axis = .horizontal

HorizontalCenterStack([...]) // axis = .horizontal; alignment = .center

TopStack([...]) // axis = .horizontal; alignment = .top

BottomStack([...]) // axis = .horizontal; alignment = .bottom


VerticalStack([...]) // axis = .vertical

VerticalCenterStack([...]) // axis = .vertical; alignment = .center

LeftStack([...]) // axis = .vertical; alignment = .leading

RightStack([...]) // axis = .vertical; alignment = .trailing

Declarative spacing:

VerticalStack([ 
    SomeLabel(),

    UIStackViewSpace(12)

    SomeButton()

    UIStackViewSpace(15)

    UIImageView(image: ...)

    SomeView()
    ...
])

@ArrangedViewBuilder functionBuilder:

HorizontalStack {
    AvatarImageView()    

    UIStackViewSpace(16)

    TopStack { 
        NameLabel()

        if user.isPremium { 
            PremiumMarkerView()
        }

        UIStackViewSpace(8)

        HStackView(tagsViews)
    }

    HorizontalCenterStack { 
        ShareButton()
        DisclosureButton()
    }.spacing(4).distribution(.fillEquality)
}

🧩 Declarative Constraint Builder

You can set constraints using the same chainable style with anchor constraint.

The return type of builder will be AutoLayoutItem – a simple storage of constants instructions. To build and activate them, just call activate() function.

let myLabel = UILabel()
    .numberOfLines(0) // -> UIView
    ...
    .heightAnchor(0) // -> AutoLayoutItem (same below)
    .topAnchor(16.from(anotherView.topAnchor))
    .leftAnchor(24)
    .rightAnchor(24.orLess.pririty(750))
    .verticalAnchor(backgroundView)
    .activate() // -> UIView (with applyed constraints)

🧮 Constraint Builder DSL Specification

Attributes

• constant - Int/Float/CGFloat/...

• target (only relative constraints):

• • from(target: NSLayoutAnchor) - from the outside of the view.
    Example: firstView.rightAnchor(24.from(secondView.leftAnchor))
• • to(target: NSLayoutAnchor) - from the inside of the view.
    Example: subview.leftAnchor(16.to(superview.leftAnchor))
• • without this attribute builder will apply instruction to superview.
    Example: subview.leftAnchor(16) equivalent to the previous example

• relationType

• • Equal (by default)
• • orLess
    Example: 15.orLess; 15.to(secondView.leftAnchor).orLess
• • orGreater
    Example: 15.orGreater; 15.to(secondView.leftAnchor).orGreater

• priorioty

• • 15.priority(.defaultLow)
• • or 15.priority(250)
• • ⚠️ without this attribute builder will apply instruction with priority 999

• multiplier (only dimension constraints)
  Example: headerView.heightAnchor(backgroundView.multiplied(0.5).orLess)

Final Formula:

constant.from|to(_ target: NSLayoutAnchor).priority(NSLayoutPriority).orLess|orGreater

The order of the attributes is arbitrary:

15.from(secondView.topAnchor).orLess
20.orLess.to(secondView.bottomAnchor).priority(1000)
8.priority(.required).orGreater

Extra anchors:

• horizontalAnchor – leftAnchor + rightAnchor
  Example: subview.horizontalAnchor(16)

• verticalAnchor – topAnchor + bottomAnchor
  Example: subview.verticalAnchor(16.orLess)

• centerAnchor - centerXAnchor + centerYAnchor
  Example: avatarView.centerAnchor(backgroundView)

• sizeAnchor - widthAnchor + heightAnchor
  Example: avatarView.sizeAnchor(60)

• edgesAnchors(insets: UIEdgeInsets, to target: UIView?, priority: UILayoutPriority) - combination of the left|top|right|bottom anchors.

• layout(_ builder: (UIView) -> AutoLayoutItem) - self-related anchor
  Example: myView.layout({ $0.heightAnchor($0.widthAnchor) })

🧩 View/Builder Composition

private(set) weak var avatarView: UIImageView!

...

let profileView = UIView()
    .backgroundColor(.gray)
    .heightAnchor(100)
    .add({
        UIImageView()
            .assign(to: &avatarView)
            .contentMode(.scaleAspectFit)
            .sizeAnchor(40)
            .leftAnchor(16)
            .verticalAnchor(0)

        UILabel()
            .numberOfLines(2)
            .rightAnchor(0)
            .leftAnchor(8.from(avatarView.leftAnchor).priority(.required))
    })
    .activate()

Or using a convenience initializer

let profileView = UIView {
    UIImageView()
        .assign(to: &avatarView)
        .contentMode(.scaleAspectFit)
        .sizeAnchor(40)
        .leftAnchor(16)
        .verticalAnchor(0)

    UILabel()
        .numberOfLines(2)
        .rightAnchor(0)
        .leftAnchor(8.from(avatarView.leftAnchor).priority(.required))
}
.backgroundColor(.gray)
.heightAnchor(100)
.activate()

ℹ️ NOTE: if you add constraint-builders to a UIView (i.e. don't use anchor-chaining before call add(...)), constraints activations will occur immediately after adding in superview. In other words, the return type of the activate() function will be Self (i.e. UIView)

let profileView = UIView()
    .backgroundColor(.gray)
    .add({
        UIImageView()
            .assign(to: &avatarView)
            .contentMode(.scaleAspectFit)
            .sizeAnchor(40)
            .leftAnchor(16)
            .verticalAnchor(0)
        UILabel()
            .numberOfLines(2)
            .rightAnchor(0)
            .leftAnchor(8.from(avatarView.leftAnchor).priority(.required))
    }) // -> UIView (with already added subviews)
    // and you can continue chainable-configuration (for example by specifying own anchors)
    .heightAnchor(100) // -> AutoLayoutItem
    .activate() // -> UIView

How to extend chaining functionality?

First way – write type extension with function that return self:

extension MyCustomView {
    func myProperty(_ value: ValueType) -> Self {
        self.myProperty = value
        return self
    }
}

Second way – using Sourcery apply Chainable template with your custom view (see tutorial).

How this framework differs from the others?

There is huge number of layout frameworks...
The main goal of creating another one framework was not to create another one framework, but to *make tools for rapid writing of layout code
SnapKit, many people know, is one of these solutions, but I decided to make a more declarative and simple solution.\

P.S. in previous versions the Framework was based on DSL SnapKit, but now has its own, more type-safe.

This README decription is all you need to know, no redundant documentation needed.\

💉 You can easily integrate the framework into project and combine it with old/existing layout code.

Installation

CocoaPods

# Podfile
use_frameworks!

target 'YOUR_TARGET_NAME' do
    pod 'DeclarativeLayoutKit'
end

Replace YOUR_TARGET_NAME and then, in the Podfile directory, type:

$ pod install

Swift Package Manager

Create a Package.swift file.

// swift-tools-version:5.0

import PackageDescription

let package = Package(
  name: "YOUR_PROJECT_NAME",
  dependencies: [
      .package(url: "https://github.com/Ernest0-Production/DeclarativeLayoutKit.git", from: "3.0.2")
  ],
  targets: [
      .target(name: "YOUR_TARGET_NAME", dependencies: ["DeclarativeLayoutKit"])
  ]
)

Credits

• Telegram

License

DeclarativeLayoutKit is released under the MIT license. See LICENSE for details.