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https://github.com/nakiostudio/EasyPeasy

Auto Layout made easy
https://github.com/nakiostudio/EasyPeasy

auto auto-layout constraints easypeasy ios layout swift

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Auto Layout made easy

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README 

        


EasyPeasy Logo




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**EasyPeasy** is a Swift framework that lets you create *Auto Layout* constraints

programmatically without headaches and never ending boilerplate code. Besides the

basics, **EasyPeasy** resolves most of the constraint conflicts for you and also

can attach to a constraint conditional closures that are evaluated before applying

a constraint, this way you can install an *Auto Layout* constraint depending on

platform, size classes, orientation... or the state of your controller, easy peasy!



In this quick tour through **EasyPeasy** we assume that you already know the

advantages and disadvantages of the different *Auto Layout* APIs and therefore you

won't see here a comparison of the code side by side, just read and decide

whether **EasyPeasy** is for you or not.



### A touch of EasyPeasy

The example below is quite simple but shows how effortless its implementation

result using **EasyPeasy**.






First touch




### Features



* Compatible with iOS, tvOS and OS X.

* Lightweight and easy to use domain specific language.

* Resolution of *Auto Layout* conflicts.

* Fast and *hassle-free* update of constraints.

* Conditional application of constraints.

* `UILayoutGuide` and `NSLayoutGuide` support.



### Guides



* [Mastering Auto Layout with EasyPeasy I: Introduction](https://medium.com/@yaid/mastering-auto-layout-with-easypeasy-i-introduction-341f12230074)

* [Mastering Auto Layout with EasyPeasy II: Basics](https://medium.com/@yaid/mastering-auto-layout-with-easypeasy-ii-basics-3057e1db817)

* [Mastering Auto Layout with EasyPeasy III: Relationships](https://medium.com/@yaid/mastering-auto-layout-with-easypeasy-iii-relationships-91fc140e4755)

* Mastering Auto Layout with EasyPeasy IV: Priorities *(coming soon...)*

* Mastering Auto Layout with EasyPeasy V: Layout Guides *(coming soon...)*

* Mastering Auto Layout with EasyPeasy VI: Advanced *(coming soon...)*



## Table of contents



* [Installation](#installation)

* [Usage](#usage)

  * [Constants](#constants)

  * [Attributes](#attributes)

    * [DimensionAttributes](#dimensionattributes)

    * [PositionAttributes](#positionattributes)

    * [CompoundAttributes](#compoundattributes)

  * [Priorities](#priorities)

  * [Conditions](#conditions)

    * [ContextualConditions](#contextualconditions)

  * [UILayoutGuides](#uilayoutguides)

  * [Lastly](#lastly)

    * [Updating constraints](#updating-constraints)

    * [Clearing constraints](#clearing-constraints)

    * [Animating constraints](#animating-constraints)

* [Example projects](#example-projects)

* [EasyPeasy playground](#easypeasy-playground)

* [Autogenerated documentation](#autogenerated-documentation)



## Installation



### Swift compatibility

* To work with Swift 2.2 use EasyPeasy `v.1.2.1` or earlier versions of the library.

* To work with Swift 2.3 use EasyPeasy `v.1.3.1`.

* To work with Swift 3 use EasyPeasy `v.1.4.2`.

* To work with Swift 4 use EasyPeasy `v.1.8.0`.

* To work with Swift 5 use EasyPeasy `v.1.9.0` and above.

(thanks [Bas van Kuijck](https://github.com/basvankuijck)).



### Cocoapods

EasyPeasy is available through [CocoaPods](http://cocoapods.org). To install

it, simply add the following line to your Podfile:



```ruby

pod "EasyPeasy"

```



### Carthage

EasyPeasy is [Carthage](https://github.com/Carthage/Carthage) compatible.

To add **EasyPeasy** as a dependency to your project, just add the following line

to your Cartfile:



```ruby

github "nakiostudio/EasyPeasy"

```



And run ` carthage update ` as usual.



### Compatibility

**EasyPeasy** is compatible with iOS (8 and above), tvOS (9 and above) and OS X

(10.10 and above).

The framework has been tested with Xcode 7 and Swift 2.0, however don't hesitate

to report any issues you may find with different versions.



## Usage



**EasyPeasy** is a set of position and dimension attributes that you can apply

to your views. You can manage these from the  `easy` property available within all

the UI classes that work with Auto Layout (view subclasses, layout guides, etc).



For instance, to set a width of 200px to a view you would create

an attribute of class `Width` with a constant value of `200`, then the attribute

is applied to the view by using the `easy.layout(_:)` method.



```swift

myView.easy.layout(Width(200))

```



Because our view without height is nothing we can apply multiple attributes at

once as follows:



```swift

myView.easy.layout(

  Width(200),

  Height(120)

)

```



In the previous example, two attributes have been applied and therefore two constraints

created and added: a width constraint with `constant = 200` and a height constraint

with `constant = 120`.



### Constants

Without really knowing it, we have just created an **EasyPeasy** `Constant` struct

containing the constant, multipler and the relation of a `NSLayoutConstraint`.



#### Relations

**EasyPeasy** provides an easy way of creating constants with different

`NSLayoutRelations`:



* `.Equal`: it is created like in our previous example `Width(200)`.

* `.GreaterThanOrEqual`: it is created as easy as this `Width(>=200)` and it means

that our view has a width greater than or equal to 200px.

* `.LessThanOrEqual`: it is created as follows `Width(<=200)`.



#### Multipliers

There is a custom operator that eases the creation of a `NSLayoutConstraint` multiplier.

You can use it like this `Width(*2)` and means that the width of our view is two times

*something*, we will mention later how to establish the relationship with that *something*.



In addition, you can combine `multipliers` with `Equal`, `.GreaterThanOrEqual` and

`LessThanOrEqual` relations. i.e. `Width(>=10.0*0.5)` creates a `NSLayoutConstraint`

with `value = 10.0`, `relation = .GreaterThanOrEqual` and `multiplier = 0.5`, whereas

`Width(==10.0*0.5)` creates a `NSLayoutConstraint` with `value = 10.0`,

`relation = .Equal` and `multiplier = 0.5`.



### Attributes

**EasyPeasy** provides as many `Attribute` classes as attributes `NSLayoutConstraint`

have, plus something that we have called `CompoundAttributes` (we will explain these

attributes later).



#### DimensionAttributes

There are just two dimension attributes `Width` and `Height`. You can create an

*Auto Layout* relationship between your view `DimensionAttribute` and another view

by using the method `func like(view: UIView) -> Self`. Example:



```swift

contentLabel.easy.layout(Width().like(headerView))

```



That line of code will create a constraint that sets a width for `contentLabel`

equal to the `headerView` width.



#### PositionAttributes

The table below shows the different position attributes available. Because they

behave like the `NSLayoutConstraint` attributes, you can find a complete

description of them in the [Apple docs](https://developer.apple.com/library/ios/documentation/AppKit/Reference/NSLayoutConstraint_Class/#//apple_ref/c/tdef/NSLayoutRelation).



Attribute | Attribute | Attribute | Attribute

--- | --- | --- | ---

Left | Right | Top | Bottom

Leading | Trailing | CenterX | CenterY

LeftMargin | RightMargin | TopMargin | BottomMargin

LeadingMargin | TrailingMargin | CenterXWithinMargins | CenterYWithinMargins

FirstBaseline | LastBaseline | -- | --



As well as the **DimensionAttributes** have the `like:` method to establish

*Auto Layout* relationships, you can use a similar method to do the same with

**PositionAttributes**. This method is:



```swift

func to(view: UIView, _ attribute: ReferenceAttribute? = nil) -> Self

```



The example below positions `contentLabel` 10px under `headerView` with the same

left margin as `headerView`.



```swift

contentLabel.easy.layout(

  Top(10).to(headerView),

  Left().to(headerView, .Left)

)

```



#### CompoundAttributes

These attributes are the ones that create multiple `DimensionAttributes` or

`PositionAttributes` under the hood. For example, the `Size` attribute will create

a `Width` and a `Height` attributes with their width and height

`NSLayoutConstraints` respectively.



These are the `CompoundAttributes` available:



* `Size`: As mentioned before this attribute will apply a `Width` and a `Height`

attribute to the view. It can be initialized in many ways and depending on that

the result may change. These are some examples:



```swift

// Apply width = 0 and height = 0 constraints

view.easy.layout(Size())

// Apply width = referenceView.width and height = referenceView.height constraints

view.easy.layout(Size().like(referenceView))

// Apply width = 100 and height = 100 constraints

view.easy.layout(Size(100))

// Apply width = 200 and height = 100 constraints

view.easy.layout(Size(CGSize(width: 200, height: 100)))

```



* `Edges`: This attribute creates `Left`, `Right`, `Top` and `Bottom` attributes

at once. Examples:



```swift

// Apply left = 0, right = 0, top = 0 and bottom = 0 constraints to its superview

view.easy.layout(Edges())

// Apply left = 10, right = 10, top = 10 and bottom = 10 constraints to its superview

view.easy.layout(Edges(10))

// Apply left = 10, right = 10, top = 5 and bottom = 5 constraints to its superview

view.easy.layout(Edges(UIEdgeInsets(top: 5, left: 10, bottom: 5, right: 10)))

```



* `Center`: It creates `CenterX` and `CenterY` attributes. Examples:



```swift

// Apply centerX = 0 and centerY = 0 constraints to its superview

view.easy.layout(Center())

// Apply centerX = 10 and centerY = 10 constraints to its superview

view.easy.layout(Center(10))

// Apply centerX = 0 and centerY = 50 constraints to its superview

view.easy.layout(Center(CGPoint(x: 0, y: 50)))

```



* `Margins`: This attribute creates `LeftMargin`, `RightMargin`, `TopMargin` and

`BottomMargin` attributes at once. Examples:



```swift

// Apply leftMargin = 0, rightMargin = 0, topMargin = 0 and bottomMargin = 0 constraints to its superview

view.easy.layout(Margins())

// Apply leftMargin = 10, rightMargin = 10, topMargin = 10 and bottomMargin = 10 constraints to its superview

view.easy.layout(Margins(10))

// Apply leftMargin = 10, rightMargin = 10, topMargin = 5 and bottomMargin = 5 constraints to its superview

view.easy.layout(Margins(UIEdgeInsets(top: 5, left: 10, bottom: 5, right: 10)))

```



* `CenterWithinMargins`: It creates `CenterXWithinMargins` and `CenterYWithinMargins`

attributes. Examples:



```swift

// Apply centerXWithinMargins = 0 and centerYWithinMargins = 0 constraints to its superview

view.easy.layout(CenterWithinMargins())

// Apply centerXWithinMargins = 10 and centerYWithinMargins = 10 constraints to its superview

view.easy.layout(CenterWithinMargins(10))

// Apply centerXWithinMargins = 0 and centerYWithinMargins = 50 constraints to its superview

view.easy.layout(CenterWithinMargins(CGPoint(x: 0, y: 50)))

```



### Priorities



The `Priority` enum does the same function as `UILayoutPriority` and it's shaped

by five cases:

* `low`: it creates an *Auto Layout* priority with `Float` value `1`.



* `medium`: it creates an *Auto Layout* priority with `Float` value `500`.



* `high`: it creates an *Auto Layout* priority with `Float` value `750`.



* `required`: it creates an *Auto Layout* priority with `Float` value `1000`.



* `custom`: it specifies the *Auto Layout* priority defined by the

developer in the case associated value `value`. Example: `.custom(value: 650.0)`.



In order to apply any of these priorities to an `Attribute`, the method

`.with(priority: Priority)` must be used. The following example gives an

`UILayoutPriority` of `500` to the `Top` `Attribute` applied to `view`:



```swift

view.easy.layout(Top(>=50).with(.medium))

```



You can also apply a `Priority` to an array of `Attributes` (this operation will

override the priorities previously applied to an `Attribute`).



```swift

view.easy.layout([

  Width(200),

  Height(200)

].with(.medium))

```



### Conditions

One of the peculiarities of **EasyPeasy** is the usage of `Conditions` or closures

that evaluate whether a constraint should be applied or not to the view.



The method `when(condition: Condition)` sets the `Condition` closure to an `Attribute`.



There is plenty of use cases, the example below shows how to apply different

constraints depending on a custom variable:



```swift

var isCenterAligned = true

...

view.easy.layout(

  Top(10),

  Bottom(10),

  Width(250),

  Left(10).when { !isCenterAligned },

  CenterX(0).when { isCenterAligned }

)

```



#### Condition re-evaluation

These `Condition` closures can be re-evaluated during the lifecycle of a view,

to do so you just need to call the convenience method `easy.reload()`.



```swift

view.easy.reload()

```



Bare in mind that these `Condition` closures are stored in properties therefore

you need to capture those variables you access within the closure. For example:



```swift

descriptionLabel.easy.layout(

  Height(100).when { [weak self] in

    return self?.expandDescriptionLabel ?? false

  }

)

```



You can also apply a `Condition` to an array of `Attributes` (this operation will

override the `Conditions` previously applied to an `Attribute`).



```swift

view.easy.layout([

  Width(200),

  Height(240)

].when { isFirstItem })



view.easy.layout([

  Width(120),

  Height(140)

].when { !isFirstItem })

```



#### ContextualConditions

This iOS only feature is a variant of the `Condition` closures that receive no

parameters and return a boolean value. Instead, a `Context` struct is passed

as parameter providing some extra information based on the `UITraitCollection`

of the `UIView` the `Attributes` are going to be applied to.



The properties available on this `Context` struct are:



* `isPad`: true if the current device is iPad.

* `isPhone`: true if the current device is iPhone.

* `isHorizontalVerticalCompact`: true if both horizontal and vertical size

classes are `.Compact`.

* `isHorizontalCompact`: true if the horizontal size class is `.Compact`.

* `isVerticalCompact`: true if the vertical size class is `.Compact`.

* `isHorizontalVerticalRegular`: true if both horizontal and vertical size

classes are `.Regular`.

* `isHorizontalRegular`: true if the horizontal size class is `.Regular`.

* `isVerticalRegular`: true if the vertical size class is `.Regular`.



This is an example of `ContextualConditions` applied to an array of

`Attributes`:



```swift

view.easy.layout([

  Size(250),

  Center(0)

].when { $0.isHorizontalRegular })



view.easy.layout([

  Top(0),

  Left(0),

  Right(0),

  Height(250)

].when { $0.isHorizontalCompact })

```



##### ContextualCondition re-evaluation

As we have seen before, you can re-evaluate a `Condition` closure by calling

the `easy.reload()` convenience method. This also applies to

`ContextualConditions`, therefore if you want your constraints to be updated

upon a change on your view `UITraitCollection` then you need to call the

`easy.reload()` method within `traitCollectionDidChange(_:)`.



Alternatively, **EasyPeasy** can do this step for you automatically. This is

disabled by default as it requires method swizzling; to enable it simply

**compile the framework** adding the compiler flags `-D EASY_RELOAD`.



### UILayoutGuides

Since the version *v.0.2.3* (and for iOS 9 projects and above) **EasyPeasy**

integrates `UILayoutGuides` support.



#### Applying constraints

Applying a constraint to an `UILayoutGuide` is as easy as we have discussed in the

previous sections, just apply the **EasyPeasy** attributes you want using the

`easy.layout(_:)` method.



```swift

func viewDidLoad() {

  super.viewDidLoad()



  let layoutGuide = UILayoutGuide()

  self.view.addLayoutGuide(layoutGuide)



  layoutGuide.easy.layout(

    Top(10),

    Left(10),

    Right(10),

    Height(100).when { Device() == .iPad },

    Height(60).when { Device() == .iPhone }

  )

}

```



As you can see, all the different attributes and goodies **EasyPeasy** provides for

`UIViews` are also applicable to `UILayoutGuides`.



#### Connecting UILayoutGuides and UIViews

As mentioned in the [Attributes](#attributes) section you can create constraint

relationships between an `UIView` attribute and other `UIViews` attributes using

the methods `to(_:_)` and `like(_:_)`. Now you can take advantage of those methods

to create a relationship between your `UIView` attributes and an `UILayoutGuide`.



```swift

let layoutGuide = UILayoutGuide()

let separatorView: UIView

let label: UILabel



func setupLabel() {

  self.label.easy.layout(

    Top(10).to(self.layoutGuide),

    CenterX(0),

    Size(60)

  )



  self.separatorView.easy.layout(

    Width(0).like(self.layoutGuide),

    Height(2),

    Top(10).to(self.label),

    CenterX(0).to(self.label)

  )

}

```



### Lastly

Finally but not less important in this section we will explain how to interact

with `Attributes` once they have been applied to an `UIView` using the

`easy.layout(_:)` method.



#### Updating constraints

We briefly mentioned in the introductory section that **EasyPeasy** solves most

of the constraint conflicts and it's true. Usually, in order to update a constraint

or the constant of a constraint you have to keep a reference to your

`NSLayoutConstraint` and update the constant when needed. With **EasyPeasy** you

just need to apply another `Attribute` to your `UIView` of the same or different

type. In the example below we have two methods, the one in which we setup our

constraints `viewDidLoad()` and a method in which we want to update the `Top`

attribute of our `headerView`.



```swift

func viewDidLoad() {

  super.viewDidLoad()



  headerView.easy.layout(

    Top(0),

    Left(0),

    Right(0),

    Height(60)

  )

}



func didTapButton(sender: UIButton?) {

  headerView.easy.layout(Top(100))

}

```



That's it! we have updated our `Top` constraint without caring about keeping

references or installing/uninstalling new constraints.



However, there is some cases in which **EasyPeasy** cannot prevent a conflict (at

least for now). This is when multiple constraints cannot be satisfied, i.e. existing

a `Left` and `Right` constraints it's also applied a `Width` constraint (all of them

with the same priority). But **EasyPeasy** is smart enough to prevent conflicts,

i.e. when replacing a `Left` and `Right` attributes with a `CenterX` attribute.



#### Clearing constraints

**EasyPeasy** provides a method extending `UIView` that clears all the constraints

installed in an `UIView` by the framework. This method is `func easy.clear()`.



```swift

view.easy.clear()

```



#### Animating constraints

Animating constraints with **EasyPeasy** is very straightforward, just apply one

or more `Attributes` to your view within an animation block and you are ready to

go, without worrying about constraint conflicts. Example:



```swift

UIView.animateWithDuration(0.3) {

  view.easy.layout(Top(10))

  view.layoutIfNeeded()

}

```



## Example projects



Don't forget to clone the repository and run the iOS and OS X example projects

to see **EasyPeasy** in action.







  

  

    Demo iOS

  

  

    Demo macOS

  

  



*Note:* the messages in the demo app aren't real and the appearance of

those *Twitter* accounts no more than a tribute to some kickass developers :)



## EasyPeasy playground



Alternatively, you can play with **EasyPeasy** cloning the *Playground* project

available [here](https://github.com/nakiostudio/EasyPeasy-Playground).





Playground




## Autogenerated documentation



**EasyPeasy** is a well documented framework and therefore all the documented

classes and methods are available in [Cocoadocs](http://cocoadocs.org/docsets/EasyPeasy).



## Author



Carlos Vidal - [@nakiostudio](https://twitter.com/nakiostudio)



## License



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