Visibility Toggler UIView Extension

VisibilityToggler+UIView.swift

//
//  VisibilityToggler+UIView.swift
//

private var associatedPropertyHeight: CGFloat = 0
private var associatedPropertyWidth: CGFloat = 0

extension UIView {

	fileprivate var visibilityConstraintIdentifier: String { return "UIVisibilityGenerated" }

	fileprivate var height: CGFloat? {
		get {
			return objc_getAssociatedObject(self, &associatedPropertyHeight) as? CGFloat
		}
		set(newValue) {
			objc_setAssociatedObject(self, &associatedPropertyHeight, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
		}
	}

	fileprivate var width: CGFloat? {
		get {
			return objc_getAssociatedObject(self, &associatedPropertyWidth) as? CGFloat
		}
		set(newValue) {
			objc_setAssociatedObject(self, &associatedPropertyWidth, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
		}
	}

	func updateConstrainedHeight(_ height: CGFloat) {
		if let constraint = getConstraintBy(type: .height) {
			constraint.constant = height
		}
		self.height = height
	}

	func updateConstrainedWidth(_ width: CGFloat) {
		if let constraint = getConstraintBy(type: .width) {
			constraint.constant = width
		}
		self.width = width
	}

	func zeroHeight(animated: Bool = false) {
		if animated {
			superview?.layoutIfNeeded()
			UIView.animate(withDuration: 0.3, animations: {
				self.zeroHeightContraint()
			})
		} else {
			zeroHeightContraint()
		}
	}

	private func zeroHeightContraint() {
		clipsToBounds = true
		if let constraint = getConstraintBy(type: .height) {
			if constraint.constant > 0 {
				self.height = constraint.constant
			}
			constraint.constant = 0
			superview?.layoutIfNeeded()
		}
	}

	func zeroWidth() {
		clipsToBounds = true
		if let constraint = getConstraintBy(type: .width) {
			if constraint.constant > 0 {
				self.width = constraint.constant
			}
			constraint.constant = 0
			superview?.layoutIfNeeded()
		}
	}

	func restoreHeight(animated: Bool = false) {
		if animated {
			superview?.layoutIfNeeded()
			UIView.animate(withDuration: 0.3, animations: {
				self.restoreHeightConstraint()
			})
		} else {
			restoreHeightConstraint()
		}
	}

	private func restoreHeightConstraint() {
		if let constraint = getConstraintBy(type: .height) {
			if constraint.constant == 0 {
				if self.height != nil {
					constraint.constant = self.height!
				} else {
					constraint.constant = self.frame.height
				}
				if constraint.identifier == visibilityConstraintIdentifier {
					removeConstraint(constraint)
				}
				superview?.layoutIfNeeded()
			}
		}
	}

	func restoreWidth() {
		if let constraint = getConstraintBy(type: .width) {
			if constraint.constant == 0 {
				if self.width != nil {
					constraint.constant = self.width!
				} else {
					constraint.constant = self.frame.width
				}
				if constraint.identifier == visibilityConstraintIdentifier {
					removeConstraint(constraint)
				}
				superview?.layoutIfNeeded()
			}
		}
	}

	func getConstant(type: NSLayoutAttribute) -> CGFloat? {
		guard let constraint = getConstraintBy(type: type) else { return nil }
 		return constraint.constant
	}

	func isVisible() -> Bool {
		if let heightConstraint = getConstraintBy(type: .height, createNewIfNotFound: false) {
			return heightConstraint.constant != 0 && isHidden == false
		} else if let widthConstraint = getConstraintBy(type: .width, createNewIfNotFound: false) {
			return widthConstraint.constant != 0 && isHidden == false
		}
		return isHidden == false
	}

	fileprivate func getConstraintBy(type: NSLayoutAttribute, createNewIfNotFound: Bool = true) -> NSLayoutConstraint? {
		var returnConstraint: NSLayoutConstraint? = nil
		for constraint in self.constraints {
			if constraint.firstAttribute == type && type(of: constraint) == NSLayoutConstraint.self {
				if returnConstraint == nil {
					returnConstraint = constraint
				} else {
					AppLogWarning("Operating on view with multiple \(type.rawValue) constraints: \(constraint)")
				}
			}
		}
		if returnConstraint == nil && createNewIfNotFound {
			let newConstraint = NSLayoutConstraint(item: self, attribute: type, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 0)
			newConstraint.identifier = visibilityConstraintIdentifier
			addConstraint(newConstraint)
			returnConstraint = newConstraint
		}
		return returnConstraint
	}
}