ConstraintLib

Swift library that simplifies interacting with Xcode Constraints by adding the following features:

• Add constraints in swift with a understandable function
• Find constraints from code
• Animate swift constraints changes
• Remove constraints from it's superview

This library now requires Swift 4.

Background Info

I love making custom views and with custom animation. But everytime I do so I find myself writing a lot of constraint code just to manage subviews, create constraint properties and perform animations. Using this category / lib, I managed to make my custom views cude a lot more simple.

Usage

This module contains extensions on: UIView, UIViewController & NSLayoutConstraint.

Example 1: Create a view with NSLayoutConstraint properties

When a view has a frame you can easily pin the edges to its superview with the frame's values.
Always make sure you first add the view to its superview before pinning constraints.

let newView = UIView(frame: CGRect(x: 50.0, y: 50.0, width: 100.0, height: 100.0))
self.view.addSubview(newView)
let topConstraint = newView.pin(.top)
let leftConstraint = newView.pin(.left)
let heightConstraint = newView.pin(.height)
let widthConstraint = newView.pin(.width)

Example 2: Create a view without NSLayoutConstraint properties

If you don't need the constraint properties, then this syntax can also be used.

let newView = UIView(frame: CGRect(x: 50.0, y: 50.0, width: 100.0, height: 100.0))
self.view.addSubview(newView)
newView.pin([.top, .left, .height, .width]

Example 3: Create a view and provide constant values

Alternatively, values can also be provided in the pin command.

Full Format:

let newView1 = UIView()
self.view.addSubview(newView1)
let topConstraint = newView1.pin(.top, constant: 50.0)
let leftConstraint = newView1.pin(.left, constant: 50.0)
let heightConstraint = newView1.pin(.height, constant: 100.0)
let widthConstraint = newView1.pin(.width, constant: 100.0)

Compact format:

let newView2 = UIView()
self.view.addSubview(newView2)
newView2.pin([.top: 50.0, .left: 50.0, .height: 100.0, .width: 100.0]

Example 4: Create a view with a relation to another view

To create a view newView2 where it's top will stick 30 pixels away from the bottom of view newView1

let newView1 = UIView()
self.view.addSubview(newView1)
newView1.pin([.height, .width, .centerX, .centerY])

let newView2 = UIView()
self.view.addSubview(newView2)
newView2.pin([.left: 100.0, .right: 100.0, .height: 30.0, .topTo(newView1): 30.0])

Example 5: Pin to the top and/or bottom UILayoutGuide

To pin a view to the ViewController's layout guide's, allowing a view to always stick to the status bar and even the in-call status bar. Use

let topLayoutGuideConstraint = newView1.pin(.topLayoutGuide, constant: 0.0)
let bottomLayoutGuideConstraint = newView1.pin(.bottomLayoutGuide, constant: 0.0)

Or of course one of the other formats.

let topLayoutGuideConstraint = newView1.pin(.topLayoutGuide)
newView1.pin([.topLayoutGuide, .bottomLayoutGuide, .left, .right]
newView1.pin([.topLayoutGuide: 0.0, .bottomLayoutGuide: 0.0, .left: 0.0, .right: 0.0]

Example 6: Default multiplier

The default multiplier can only be modified in the single line creator

let newView1 = UIView()
self.view.addSubview(newView1)
let topConstraint = newView1.pin(.top, constant: 50.0, multiplier: 2.0)

After initialisation, the multiplier can be modified by using the multiplier attribute

newView1.constraint(.top)?.multiplier = 1.5

Example 7: Find a NSLayoutConstraint from a view

Constraints can be found in the following way

let leftConstraint = view1.constraint(.left)
let rightConstraint = view1.constraint(.right)
let topConstraint = view1.constraint(.top)
let bottomConstraint = view1.constraint(.bottom)
let widthConstraint = view1.constraint(.width)
let heightConstraint = view1.constraint(.height)
let centerXConstraint = view1.constraint(.centerX)
let centerYConstraint = view1.constraint(.centerY)

let leftToView2Constraint = view1.constraint(.leftTo(view2))
let rightToView2Constraint = view1.constraint(.rightTo(view2))
let topToView2Constraint = view1.constraint(.topTo(view2))
let bottomToView2Constraint = view1.constraint(.bottomTo(view2))

let equalwidthToView2Constraint = view1.constraint(.equalWidth(view2))
let equalHeightToView2Constraint = view1.constraint(.equalHeight(view2))

Finding a NSLayoutConstraint that is based on a topLayoutGuide or bottomLayoutGuide is not available yet.

Example 8: Animate constraint changes

The animateConstraints functions works similar to the UIView.animate(withDuration: TimeInterval, animations: Swift.Void)
With as only exception that the animateConstraints must be called on the highest UIView, to make it easier this function has also been added as extension to UIViewController.
Next to that there is an optional block for normal animation, one for constraint animations and an optional completion block.

animateConstraints(duration: 1.0, constraints: {
    
    /* Only contraint changes will be animated in this block */
    
    view1?.constraint(.left)?.constant = 150.0
                    
}, animations: {
    
    /* Other changes will be animated from this block */
    
    view1?.backgroundColor = UIColor.blue
})

Example 9: Remove a constraint

Remove a left or leading constraint

view1.constraint(.left)?.remove()

Remove a horizontal constraint from the right side of view1 to the left side of view2

view1.constraint(.rightTo(view2))?.remove()

More demos?

Clone the repository, open ConstraintLib.xcodeproj and build the demo project

Development Info

Please document code changes in unit tests and make sure all tests are green.

License

This project is released under the Apache-2.0 license.