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https://github.com/Skyvive/Swiftstraints

Auto Layout In Swift Made Easy
https://github.com/Skyvive/Swiftstraints

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Auto Layout In Swift Made Easy

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# Swiftstraints



`Swiftstraints` can turn verbose auto-layout code:

```swift

let constraint = NSLayoutConstraint(item: blueView,

                               attribute: NSLayoutAttribute.Width,

                               relatedBy: NSLayoutRelation.Equal,

                                  toItem: redView,

                               attribute: NSLayoutAttribute.Width,

                              multiplier: 1.0,

                                constant: 0.0)

```

Into one just one line of code:

```swift

let constraint = blueView.widthAnchor == redView.widthAnchor

```

Or transform your less than consise visual format language code:

```swift

let constraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|[leftView]-10-[rightView]|",

                               options: NSLayoutFormatOptions(0),

                               metrics: nil,

                               views: ["leftView":leftView, "rightView":rightView])

```

Into the following:

``` swift

let constraints = NSLayoutConstraints("H:|[\(leftView)]-10-[\(rightView)]|")

```

That was easy!



## Installation



`Swiftstraints` is available through [CocoaPods](http://cocoapods.org). To install, simply include the following lines in your podfile:

```ruby

use_frameworks!

pod 'Swiftstraints'

```

Be sure to import the module at the top of your .swift files:

```swift

import Swiftstraints

```

Alternatively, clone this repo or download it as a zip and include the classes in your project.



## Constraints



With `Swiftstraints` you can create constraints that look just Apple's generic constraint definition:

```swift

item1.attribute1 = multiplier × item2.attribute2 + constant

```

`Swifstraints` utilizes the new layout anchors introduced in iOS 9:

```swift

let view = UIView()

view.widthAnchor

view.heightAnchor

view.trailingAnchor

view.centerXAnchor

etc...

```

`Swiftstraints` implements operator overloading so that you can easily create custom constraints:

```swift

let blueView = UIView()

let redView = UIView()

let constraint = blueView.heightAnchor == redView.heightAnchor

```

Just as you would expect, you can specify a multiplier:

```swift

let constraint = blueView.heightAnchor == 2.0 * redView.heightAnchor

```

Or add a constant:

```swift

let constraint = blueView.heightAnchor == redView.heightAnchor + 10.0

```

You can specify inequalities:

```swift

let constraint = blueView.heightAnchor <= redView.heightAnchor

```

And you can define constant constraints if you so choose:

```swift

let constraint = blueView.heightAnchor == 100.0

```

Swiftstraints can readily compute relatively complex constraints:

```swift

let constraint = blueView.heightAnchor * 1.4 - 5.0 >= redView.heightAnchor / 3.0 + 400

```

It's really easy.



## Visual Format Language



Apple provides an API that lets you create multiple constraints simultaneously with the Visual Format Language. As we saw before it can be a little cumbersome:

```swift

let constraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|[leftView]-10-[rightView]|",

                               options: NSLayoutFormatOptions(0),

                               metrics: nil,

                               views: ["leftView":leftView, "rightView":rightView])

```

`Swiftstraints` uses string interpolation to let you specify the same constraints in one line of code:

```swift

let constraints = NSLayoutConstraints("H:|[\(leftView)]-10-[\(rightView)]|")

```

`Swiftstraints` also extends `UIView` so that you can add constraints easily using the interpolated string format:

```swift

superview.addConstraints("H:|[\(leftView)]-10-[\(rightView)]|")

```

Super easy, super simple.

## Revision History



* 3.0.1 - Bug fixes and limited iOS 8 support (Thank you catjia1011)

* 3.0.0 - Updated to Swift 3

* 2.2.0 - Added support for UILayoutPriority

* 2.1.0 - Fixed a view reference bug and added a new convenience method for adding constraints

* 2.0.2 - Added support for tvOS target.

* 2.0.1 - Updated to include support for axis anchors, increased test coverage and more documentation.

* 2.0.0 - Updated for Swift 2.0 and iOS 9. Now uses layout anchors for simple constraints and string interpolation for Visual Format Language constraints.

* 1.1.0 - Minor API tweaks

* 1.0.0 - Initial Release



## Author



Brad Hilton, [email protected]



## License



Swiftstraints is available under the MIT license. See the LICENSE file for more info.