ConstraintFormatter

ConstraintFormatter is a library to unify visual constraints and constraints based on attributes for Auto Layout.

It's really verbose to write NSLayoutConstraints based on attributes and with this library you can easily write and mix them with visual constraints. Something like this:

#import "ConstraintFormatter.h"

...

id views = @{@"view1": view1, @"view2": view2};
id metrics = @{@"margin": @10};
id formats = @[@"view1.bottom == view2.top + margin",
               @"view1.centerX == superview.centerX",
               @"H:|-margin-[view1]-margin-|",
               @"H:|[view2]|"];

[view addConstraintsWithFormats:formats
                          views:views
                        metrics:metrics];

As you see, the views and metrics are used to define the constraints. Also it's worth to know the library calls setTranslatesAutoresizingMaskIntoConstraints:NO in all views for you.

Attributes

Standard

• left
• right
• top
• bottom
• width
• height
• centerX
• centerY
• baseline
• leading
• trailing

Special

center

Shortcut for centerX and centerY:

@"view2.center == view1.center"

To define offsets for centerX and centerY, provide them inside parenthesis:

@"view2.center == view1.center(40, 40)"

edges

Shortcut to top, left, bottom, right:

@"view1.edges == superview.edges"

To define insets to top, left, bottom, right, provide them inside parenthesis:

@"view1.edges == superview.edges(25, 35, 25, 35)"

size

Shortcut to width and height:

@"view1.size == view2.size"

To specify values for width and height with offset, provide them inside parenthesis:

@"view1.size == view2.size(50, 50)"

To specify values for width and height, provide them inside parenthesis:

@"view1.size == (50, 50)"

Optional

It's optional to specify the attribute if the constraint uses the same attribute in both views:

view1.centerX == view2.centerX
// is the same as
view1.centerX == view2

Relations

• ==

• =

• <=

Specifying relation between two views:

@"view1.centerX == view2.centerX"

Specifying the value of an attribute for one view:

@"view1.width >= 30"

Constants

• /

Use + or - to define constants:

@"view1.centerX == view2.centerX + 10"
@"view1.centerY == view2.centerY - 10"

Use * to define multipliers:

@"view1.width == view2.width * 0.5"

You can also use / to define multipliers:

@"view1.width == view2.width / 2"

You can mix constants and multipliers:

@"view1.width == view2.width * 0.5 - 10"

Superview

If you want to reference the view which all constraints are being added, just use 'superview':

@"view1.centerX == superview.centerX"

Priority

Priority of the constraint can be set as the following:

@"view1.width@750 == view2.width"

How to contribute

Fork and clone the repo, then:

gem install cocoapods
cd Tests
pod install
open ConstraintFormatter.xcworkspace

To run the tests, just command+u or go to menu Product -> Test.

To run the example app just command+r or Product -> Run.

To edit the library files just open the Project Navigator and edit the files under Pods -> Development Pods -> ConstraintFormatter

About

ConstraintFormatter is supported by the team at Hashrocket, a multidisciplinary design & development consultancy. If you'd like to work with us or join our team, don't hesitate to get in touch.