iOS Swift Extension for easily hiding/showing UIViews constrained using Auto Layout

Readme.md

If you are an iOS developer and want to do something very simple, such as hide/show a UIView while using Auto Layout, you'll find that UIKit doesn't give you much help. This extension adds simple, stateful show/hide functionality to any UIView.

Usage

1. Add HideableUIView.swift to your project.
2. Lay out and constrain your views as desired.
3. Add failover constraints to handle the absense of the view you want to hide. (Constraints that use ≥ and ≤ are great for this.)

Example Layout

This is an example layout where you have a button and a label side-by-side, which are then constrained to the left side of the superview. We want pressing the [button] to hide the [label]. Once you get the basic constraints set up, add a trailing edge constraint to the button and attach it to the super view. Set the failover constraint value to ≥ 8. This will make the button automatically adjust horizontally to the absense of the [label].

Basic Constraints

|-------------------|
|     |        |    |
|  [button]-[label]-|
|     |        |    |
|-------------------|

Failover Constraint

|----------------|
|                |
|  [button]-(≥8)-|
|                |
|----------------|
OR
|-------------------|
|                   |
|  [button]-(8@999)-|
|                   |
|-------------------|

HideableUIView.swift

//
//  HideableUIView.swift
//  Albert Bori
//
//  Created by Albert Bori on 5/19/15.
//  Copyright (c) 2015 Albert Bori under the MIT license.
//  Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
//  
//  The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
//  
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

import UIKit

private var hideableUIViewConstraintsKey: UInt8 = 0

extension UIView {
    
    private var _parentConstraintsReference: [AnyObject]! {
        get {
            return objc_getAssociatedObject(self, &hideableUIViewConstraintsKey) as? [AnyObject] ?? []
        }
        set {
            objc_setAssociatedObject(self, &hideableUIViewConstraintsKey, newValue, objc_AssociationPolicy(OBJC_ASSOCIATION_RETAIN))
        }
    }
    
    func hideView() {
        self.hidden = true
        
        if let parentView = self.superview where _parentConstraintsReference.count == 0 {
            //get the constraints that involve this view to re-add them when the view is shown
            if let parentConstraints = parentView.constraints() as? [NSLayoutConstraint] {
                for parentConstraint in parentConstraints {
                    if parentConstraint.firstItem === self || parentConstraint.secondItem === self {
                        _parentConstraintsReference.append(parentConstraint)
                    }
                }
            }
            
            parentView.removeConstraints(_parentConstraintsReference)
        }
    }
    
    func showView() {
        //reapply any previously existing constraints
        if let parentView = self.superview {
            parentView.addConstraints(_parentConstraintsReference)
        }
        
        _parentConstraintsReference = []
        self.hidden = false
    }
}

Nice!
Does anybody something similar for ObjC?
Thanks.

doesn't work for me now