StructuredLayout: structural layout for existing UIKit and SnapKit projects

Community Showcase
1

Hi everyone,

I’ve released StructuredLayout, a small Swift package that adds a declarative structural layout layer to existing UIKit projects.

The main use case is a codebase that already uses SnapKit and wants to improve layout readability incrementally, without migrating the screen to SwiftUI or replacing the existing constraint tool.

The idea

A layout is expressed with Row, Column, HStack, VStack, ZStack, and Spacer:

view.sl.layout {
    VStack(spacing: 12) {
        titleLabel

        HStack(spacing: 8, alignment: .center) {
            avatarView.size(48)
            detailLabel.expand()
            actionButton
        }
    }
}

The result builder produces native Auto Layout constraints. Structural nodes use UILayoutGuide boundaries, so they do not add layout-only container UIView instances.

Design boundaries

  • It is intended for gradual adoption in UIKit/SnapKit applications.
  • It does not replace SnapKit. Special relationships can continue to use snp.makeConstraints.
  • Row/Column and HStack/VStack are equivalent naming styles.
  • It is SwiftUI-like at the API surface, but it is not a SwiftUI runtime: there is no state-driven diffing, view identity, environment, or replacement for UIKit.
  • The core package has no third-party dependencies.

Concrete comparison

The repository contains two implementations of the same Profile Card, using the same 10 business UIViews:

  • SnapKit-only layout: 48 non-blank layout lines
  • StructuredLayout: 29 non-blank layout lines
  • Reduction in that example: 39.6%

The compared regions are marked directly in the source, and the README includes both a generated code comparison image and a short GIF that switches between the two implementations.

I also added an isolated benchmark target. In one Debug / iPhone 17 Simulator / iOS 26.5 snapshot, layout installation measured:

  • SnapKit: 0.487 ms per card
  • StructuredLayout: 0.564 ms per card
  • Increment: about 0.076 ms per card

This is a development benchmark snapshot, not a claim that the DSL is faster than SnapKit or native Auto Layout. The main trade-off is a small abstraction cost for less repetitive and more structural layout code.

Current status

Version 0.1.5 supports iOS 14+, Swift 5.9+, Swift Package Manager, nested stacks, alignment/distribution, padding, sizing, expansion, conditionals, loops, layout handles, and SnapKit interoperability.

The roadmap currently includes Grid/wrapping layouts, responsive updates, constraint animation, and explicit guidance for reusable table/collection view cells.

Repository: GitHub - swifter09/StructuredLayout: A structured Row, Column and ZStack layout DSL for existing UIKit and SnapKit projects. · GitHub

I’d especially appreciate feedback from teams maintaining larger UIKit/SnapKit codebases: which API edges would block gradual adoption, and which roadmap item would be most useful first?