
Align introduces a better alternative to Auto Layout anchors.
- Semantic. Align APIs focus on your goals, not the math behind Auto Layout constraints.
- Powerful. Create multiple constraints with a single line of code.
- Type Safe. Makes it impossible to create invalid constraints, at compile time.
- Fluent. Concise and clear API that follows Swift API Design Guidelines.
- Simple. Stop worrying about
translatesAutoresizingMaskIntoConstraints
and constraints activation.
To give you a taste of what the semantic APIs look like, here is an example:
view.anchors.edges.pin(insets: 20, alignment: .center)

Getting Started
The entire library fits in a single file with around 300 lines of code. You can simply drag-n-drop it into your app if you'd like. For more installation options, see Installation Guide.
- Anchors ‣ Introduction · Core API · Semantic API
- Anchor Collections ‣ Edges · Center · Size
- Advanced · Requirements · Why Align
Introduction
Anchors (Anchor<Type, Axis
) represent layout attributes of a view including edges, dimensions, axis, and baselines. You use anchors to create constraints. The Align APIs fit in the following quadrant:

Core API allows you to create constraints by setting relations between one or more anchors, there APIs are similar to what NSLayoutAnchor
provides. Semantic API is a high-level API that focus on your goals, such as pinning edges to the container, aligning the view, setting spacing between views, etc.
Both of these types of APIs are designed to be easily discoverable using Xcode code completions. There is also a cheat sheet available, as well as an illustrated guide located in this README.

Anchors
Core API
// Align two views along one of the edges
a.anchors.leading.equal(b.anchors.leading)
// Other options are available:
// a.anchors.leading.greaterThanOrEqual(b.anchors.leading)
// a.anchors.leading.greaterThanOrEqual(b.anchors.leading, constant: 10)
// Set height to the given value (CGFloat)
a.anchors.height.equal(30)

Align automatically sets translatesAutoresizingMaskIntoConstraints
to false
for every view that you manipulate using it, so you no longer have to worry about it.
Align also automatically activates the created constraints. Using (NSLayoutConstraint.active(_:)
is typically slightly more efficient than activating each constraint individually. To take advantage of this method, wrap your code into Constrains
initializer.
Constraints {
// Create constraints in this closure
}
Align has full test coverage. If you'd like to learn about which constraints (
NSLayoutConstraint
) Align creates each time you call one of its methods, test cases are a great place to start.
Align also allows you to offset and multiply anchors. This is a lightweight operation with no allocations involved.
// Offset one of the anchors, creating a "virtual" anchor
b.anchors.leading.equal(a.anchors.trailing + 20)
// Set aspect ratio for a view
b.anchors.height.equal(a.anchors.width * 2)

Semantic API
// Set spacing between two views
a.anchors.bottom.spacing(20, to: b.anchors.top)
// Pin an edge to the superview
a.anchors.trailing.pin(inset: 20)

Clamps the dimension of a view to the given limiting range.
a.anchors.width.clamp(to: 40...100)

Anchor Collections
With Align, you can manipulate multiple edges at the same time, creating more than one constraint at a time.
Edges
pin()
is probably the most powerful and flexible API in Align.
view.anchors.edges.pin(insets: 20)
// Same as the following:
view.anchors.edges.pin(
to: view.superview!
insets: EdgeInsets(top: 20, left: 20, bottom: 20, trailing: 20),
alignment: .fill
)

By default, pin()
method pin the edges to the superview of the current view. However, you can select any target view or layout guide:
// Pin to superview
view.anchors.edges.pin()
// Pin to layout margins guide
view.anchors.edges.pin(to: container.layoutMarginsGuide)
// Pin to safe area
view.anchors.edges.pin(to: container.safeAreaLayoutGuide)
Align also provides a convenient way to access anchors of the layout guide:
view.anchors.safeArea.top
.
By default, pin()
users .fill
alignment. There are variety of other alignments available (81 if you combine all possible options).
view.anchors.edges.pin(insets: 20, alignment: .center)

You can create constraint along the given axis.
view.anchors.edges.pin(insets: 20, axis: .horizontal, alignment: .center)

Or pin the view to to a corner.
view.anchors.edges.pin(insets: 20, alignment: .topLeading)

You can create custom alignments (see Alignment
type) by providing a vertical and horizontal component.
anchors.edges.pin(insets: 20, alignment: Alignment(vertical: .center, horizontal: .leading))

Center
a.anchors.center.align()

Size
a.anchors.size.equal(CGSize(width: 120, height: 40))
greaterThanEqual
andlessThanOrEqual
options are also available

a.anchors.size.equal(b)

Advanced
By default, Align automatically activates created constraints. Using Constraints
API, constraints are activated all of the same time when you exit from the closure. It gives you a chance to change the priority
of the constraints.
Constraints(for: title, subtitle) { title, subtitle in
// Align one anchor with another
subtitle.top.spacing(10, to: title.bottom + 10)
// Manipulate dimensions
title.width.equal(100)
// Change a priority of constraints inside a group:
subtitle.bottom.pin().priority = UILayoutPriority(999)
}
Constraints
also give you easy access to Align anchors (notice, there is no .anchors
call in the example). And if you want to not activate the constraints, there is an option for that:
Constraints(activate: false) {
// Create your constraints here
}
Requirements
Align | Swift | Xcode | Platforms |
---|---|---|---|
Align 2.0 | Swift 5.1 | Xcode 11.0 | iOS 11.0 / tvOS 11.0 / macOS 10.13 |
Align 1.1-1.2 | Swift 4.2 – 5.0 | Xcode 10.1 – 10.2 | iOS 10.0 / tvOS 10.0 |
Align 1.0 | Swift 4.0 – 4.2 | Xcode 9.2 – 10.1 | iOS 9.0 / tvOS 9.0 |
Why Align
Align strives for clarity and simplicity by following Swift API Design Guidelines. Although most of the APIs are compact, it is a non-goal to enable the most concise syntax possible.
Align is for someone who:
- Prefers fluent API that follows Swift API Design Guidelines
- Doesn't want to depend on big, complex libraries
- Prefers to have as little extensions for native classes as possible,
Align
only adds one property - Doesn't overuse operator overloads, prefers fast compile times
- Likes NSLayoutAnchor but wishes it had simpler, more fluent API which didn't require manually activating constraints
Github
link |
Stars: 242 |
Related Packages
You may find interesting
Releases
Align 2.4.1 - 2020-06-21T17:53:09
- Fix typo in
Alignment
Align 2.4.0 - 2020-06-21T17:29:24
- Add Cheat Sheet
- Remove
anchors.margins
andanchors.safeArea
APIs - Documentation improvements
Align 2.3 - 2020-06-21T01:53:03
This release focuses on filling the remaining gaps in the API.
Constraints
type now conforms toCollection
protocol (backed byArray
)- Add
Constraints
activate()
anddeactivate()
methods - Add
clamp(to limit: ClosedRange<CGFloat>)
API for dimension anchors - Add default
insets
argument forAnchorCollectionEdges
equal
method - Replace the target parameter of
AnchorCollectionEdges
equal
method withLayoutItem
- Add
AnchorCollectionEdges
variant that works withCGFloat
- Add
AnchorCollectionEdges
lessThatOrEqual()
method - Fix
AnchorCollectionCenter
lessThatOrEqual()
method - Replace the target parameter of
AnchorCollectionCenter
method withLayoutItem
- Performance optimizations
Align 2.2.1 - 2020-06-18T14:50:31
- Add a missing version of
pin()
that works withCGFloat
as insets
Align 2.2 - 2020-06-18T13:15:04
- Add missing Core APIs for collections
Align 2.1 - 2020-06-18T02:12:58
Use Migraiton Guide included in the repo to ease migration.
- Remove all deprecated APIs. If you are migrating from the previous version, consider migrating to version 2.0.0 first. It is going to guide you throught the migration.
Align 2.0 - 2020-06-18T02:00:34
Use Migraiton Guide included in the repo to ease migration.
- Add
macOS support
- Add new low-level APIs:
equal
,greaterThanOrEqual
,lessThatOrEqual
- Add
spacing()
method for alignments - Rename uncler
.al
to.anchors
- Remove
.al
version accepting closure - Add
constraints
property toConstraints
type to allow access to all of the constraints created using it - Add
activate
parameter toConstraints
initiliazer to optionally disable automatic activation of constraints - Deprecated
func edges(_ edges: LayoutEdge...)
, usepin(axis:)
insteads pin()
methods now use.leading
and.trailing
anchors intead of absolute.left
and.right
anchors. To switch to absolute anchors, useabsolute()
:view.anchors.edges.absolute()
- Remove
addSubview
family of APIs - Migrate to Swift 5.1
- Increase minimum required platform versions
Align 1.2.1 - 2019-09-01T06:19:12
- Add support for Swift Package Manager 5.0
Align 1.2 - 2019-06-20T16:42:40
- Rebrand
Align 1.1 - 2019-04-07T19:06:09
- Add Swift 5.0 support
- Remove Swift 4.0 and Swift 4.1 support
- Remove iOS 9, tvOS 9 support
Align 1.0 - 2018-10-02T06:09:07
Updated to Swift 4.2 (required) and Xcode 10.
Align 0.6 - 2018-05-21T18:11:16
A minor update to make Align a bit more ergonomic.
- Add iOS 9 and tvOS 9 compatibility (used to require iOS 10 and tvOS 10).
- Add operators for setting multipliers:
view.height.match(view.width * 2)
. - Deprecated
align(with:...)
andmatch(:...)
methods which hadoffset
andmultiplier
parameters. Operators are the preferred way to set those (more compact and more obvious what they mean). - Move phantom types (e.g.
AnchorAxisVertical
) into namespaces to reduce clutter in a global namespace.
Align 0.5.1 - 2018-03-02T12:06:03
- Improve documentation
- Improve some minor implementation details
- Update project to Xcode 9.3 recommended settings
Align 0.5 - 2018-01-10T18:25:02
- Remove Stacks and Spacers (gist)
- Remove Insets
Align 0.4 - 2017-12-29T15:51:38
pinToSuperviewMargins
methods now use margin attributes (e.g..topMargin
) and notlayoutMarginsGuide
to workaround issues on iOS 10 where layout guides are unpredictable https://stackoverflow.com/questions/32694124/auto-layout-layoutmarginsguide- Add
pinToSafeArea(of:)
family of methods which usesafeAreaLayoutGuide
on iOS 11 and fall back totopLayoutGuide
andbottomLayoutGuide
on iOS 10 addSubview
methods are no longer generic which allows for more extra flexibility when adding constraints (e.g. you can create and operate on an array of layout proxies)
Align 0.3.1 - 2017-11-18T22:11:10
A small update that focuses on improving offsetting(by:)
method.
offsetting(by:)
method now available for all anchors- Add an operator that wraps
offsetting(by:)
method (which wasn't very convenient to use by itself) - [Fix] Offsetting anchor which already has an offset now works correctly
- Split the project into two files
Align 0.3 - 2017-11-15T10:16:52
-
With new
addSubview(_:constraints:)
method you define a view hierarchy and layout views at the same time. It encourages splitting layout code into logical blocks and prevents programmer errors (e.g. trying to add constraints to views not in view hierarchy). -
Remove standalone
fillSuperview(..)
andcenterInSuperview()
family of functions. There were multiple cons of having them (e.g. more terminology to learn, hard to document and explain, inconsistent withcenter
andsize
manipulations, were not allowing to pin in a corner).
Now you can manipulate multiple edges at the same time instead:
view.addSubview(stack) {
$0.edges.pinToSuperview() // pins the edges to fill the superview
$0.edges.pinToSuperview(insets: Insets(10)) // with insets
$0.edges.pinToSuperviewMargins() // or margins
$0.edges(.left, .right).pinToSuperview() // fill along horizontal axis
$0.centerY.alignWithSuperview() // center along vertical axis
}
This is a much simpler model which removes entire layer of standalone methods available on LayoutItems
. Now you always select either an anchor
or collections of anchors
, then use their methods to add constraints. Much simpler.
- Make LayoutProxy's
base
public to enable adding custom extensions on top of it.
Align 0.2 - 2017-11-13T08:28:29
- Redesigned Align API which now follow Swift API Design Guidelines. Although most of the APIs are compact, it is a non-goal to enable the most concise syntax possible. Instead Align provides a fluent APIs that form grammatical phrases.
- Full test coverage
- Add a new comprehensive overview, full guide, and installation guide
Yalta 0.1.1 - 2017-11-09T17:27:57
Revert to original Spacer
design.
Align 0.1 - 2017-11-09T17:27:43
Initial public version.