Lightweight declarative auto-layout framework for Swift
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README.md

SwiftyLayout

GitHub license Carthage compatible GitHub release build passing

Join the chat at https://gitter.im/fhisa/SwiftyLayout

SwiftyLayout is a framework that allows to describe layout constraints (ie NSLayoutConstraint) as a simple mathematical formula in a Swift program.

About Version

  • SwiftyLayout 3 for Swift 2
  • SwiftyLayout 4 for Swift 3

Code Examples

Basic usage

Using the framework, a layout constraint that "the width of the view A is equal to minus 4.0 to 50% of the width of the Views B" follows:

viewA[.Width] == 0.5 * viewB[.Width] - 4.0

This is the same layout constraints with the following code:

NSLayoutConstraint(
    item: viewA, attribute: .Width,
    relatedBy: .Equal,
    toItem: viewB, attribute: .Width,
    multiplier: 0.5, constant: -4.0)

e.g. Aspect ratio

A layout constraint that "the aspect ratio of the view A is 3:4" follows:

viewA[.Width] * 3.0 == viewA[.Height] * 4.0

This is the same layout constraints with the following code:

NSLayoutConstraint(
    item: viewA, attribute: .Width,
    relatedBy: .Equal,
    toItem: viewA, attribute: .Height,
    multiplier: 4.0/3.0, constant: 0.0)

e.g. Specify the priority

The framework has priority specification operator ~ like the following.

innerView[.Leading] == outerView[.Leading] + 4.0 ~ 750.0

This is the same layout constraints with the following code:

var constraint = NSLayoutConstraint(
    item: innerView, attribute: .Leading,
    relatedBy: .Equal,
    toItem: outerView, attribute: .Leading,
    multiplier: 1.0, constant: 4.0)
constraint.priority = 750.0
// -> constraint

Please refer to the code for the sample application and test case, too.

Refrence Guide

ConstraintTerm

ConstraintTerm means a term that contains a view in the right side or the left side of a layout constraint. For example, a ConstraintTerm representing the width .Width of view viewA:

viewA[.Width]

viewA is a UIView instance object, .Width is a NSLayoutAttribute value. ConstraintTerm is defined as a structure such as the following:

public struct ConstraintTerm
{
    let view: UIView?
    let attribute: NSLayoutAttribute
    var multiplier: CGFloat = 1.0
    var constant: CGFloat = 0.0
}

Operators

The following table, CONSTANT means CGFloat value

operator lhs rhs value semantics
+ ConstraintTerm CONSTANT ConstraintTerm add rhs value to lhs.constant
+ CONSTANT ConstraintTerm ConstraintTerm add lhs value to rhs.constant
- ConstraintTerm CONSTANT ConstraintTerm subtract rhs value from lhs.constant
* ConstraintTerm CONSTANT ConstraintTerm multiply rhs value to lhs.multiplier and lhs.constant
* CONSTANT ConstraintTerm ConstraintTerm multiply lhs value to rhs.multiplier and rhs.constant
/ ConstraintTerm CONSTANT ConstraintTerm divide lhs.multiplier and lhs.constant by rhs value
== ConstraintTerm ConstraintTerm NSLayoutConstraint create a layout constraint that "lhs is equal to lhs"
== ConstraintTerm CONSTANT NSLayoutConstraint ditto
== CONSTANT ConstraintTerm NSLayoutConstraint ditto
<= ConstraintTerm ConstraintTerm NSLayoutConstraint create a layout constraint that "lhs is less than or equal to lhs"
<= ConstraintTerm CONSTANT NSLayoutConstraint ditto
<= CONSTANT ConstraintTerm NSLayoutConstraint ditto
>= ConstraintTerm ConstraintTerm NSLayoutConstraint create a layout constraint that "lhs is greater than or equal to lhs"
>= ConstraintTerm CONSTANT NSLayoutConstraint ditto
>= CONSTANT ConstraintTerm NSLayoutConstraint ditto
~ NSLayoutConstraint CONSTANT(Float) NSLayoutConstraint Change the priority of a layout constraint, and return the constraint

Requirements

  • Swift 2.0 (Xcode 7 or later)
  • iOS
    • iOS 8 or later / iOS 7 (by coping the source files directly)
  • Mac
    • Mac OS X 10.10 or later

Installation

There are two options.

Using Carthage

Using Carthage, it's easy to add SwiftyLayout to the project.

  • Add github "fhisa/SwiftyLayout" to your Cartfile.
  • Run carthage update
  • Add SwiftyLayout.framework in Carthage/Build/iOS to your Xcode project.

Copying source files directly (iOS 7)

  • Add this repository as a git submodule:
$ git submodule add https://github.com/fhisa/SwiftyLayout.git PATH_TO_SUBMODULE
// or
$ carthage update --use-submodules
  • Then just add references of SwiftyLayout/*.swift to your Xcode project.

TODO

license

SwiftyLayout is released under the MIT license.