FiniteStateLayoutView

FiniteStateLayoutView.swift

//
//  FiniteStateLayoutView.swift
//
//  Copyright (c) 2014 Davide De Franceschi
//
//  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

// using a negative value instead of nil because Objective-C (and Interface Builder uses that) don't support Optional types.
private let invalidState = -1

// A UIView subclass that changes it's rendering in Interface Builder depending on its currentState property. The proposed usage is to use it together with a Finite State Machine that controls the possible states and transitions. Using Int as the state identifier instead of an enum for Objective-C (and Interface Builder) compatibility.
class FiniteStateLayoutView: NibDesignable {
	// You have to override this. Suggestion is to take the value from the defined FSM.
	class func startingState() -> Int {
		NSLog("ERROR: Trying to use a method of StateLayoutView. Subclass it and override \(__FUNCTION__)")
		self.doesNotRecognizeSelector(__FUNCTION__)
		return invalidState
	}
	class func isStateValid(state: Int) -> Bool {
		return contains(self.allStates(), state)
	}
	// You have to override this. Suggestion is to take the value from the defined FSM.
	class func allStates() -> [Int] {
		NSLog("ERROR: Trying to use a method of StateLayoutView. Subclass it and override \(__FUNCTION__)")
		self.doesNotRecognizeSelector(__FUNCTION__)
		return []
	}
	// You have to override this. Suggestion is to take the value from the defined FSM.
	class func canMoveFromState(fromState: Int, toState: Int) -> Bool {
		NSLog("ERROR: Trying to use a method of StateLayoutView. Subclass it and override \(__FUNCTION__)")
		self.doesNotRecognizeSelector(__FUNCTION__)
		return false
	}
	// You have to override this. Suggestion is to define an [NSLayoutConstraint] for each state and return that.
	func constraintsForState(state: Int) -> [NSLayoutConstraint]? {
		NSLog("ERROR: Trying to use a method of StateLayoutView. Subclass it and override \(__FUNCTION__)")
		self.doesNotRecognizeSelector(__FUNCTION__)
		return .None
	}

	// Animatable.
	@IBInspectable var currentState: Int = invalidState {
		didSet {
			if oldValue != invalidState {
				if self.dynamicType.isStateValid(currentState) {
					if self.dynamicType.canMoveFromState(oldValue, toState: currentState) {
						updateStateConstraintsForTransitionFromState(oldValue, toState: currentState)
						return
					} else {
						NSLog("Can't make transition from state \(oldValue) to state \(currentState)")
					}
				} else {
					NSLog("Can't make transition to invalid state \(currentState)")
				}
				currentState = oldValue
			}
		}
	}
	// Currently only supports constraints where priority = 1000.
	private func initializeStateConstraints() {
		currentState = self.dynamicType.startingState()
		for state in self.dynamicType.allStates() {
			constraintsForState(state)!.map { $0.priority = 1 }
		}
		constraintsForState(currentState)!.map { $0.priority = 1000 }
		self.layoutIfNeeded()
	}
	// Currently only supports constraints where priority = 1000.
	private func updateStateConstraintsForTransitionFromState(fromState: Int, toState: Int) {
		constraintsForState(fromState)!.map { $0.priority = 1 }
		constraintsForState(toState)!.map { $0.priority = 1000 }
		self.layoutIfNeeded()
	}

	required init(coder aDecoder: NSCoder) {
		super.init(coder: aDecoder)
		initializeStateConstraints()
	}
	override init(frame: CGRect) {
		super.init(frame: frame)
		initializeStateConstraints()
	}
}

FSLVExample.swift

//
//  FSLVExample.swift
//  FSLVExample
//
//  Created by Davide De Franceschi on 16/11/14.
//  Copyright (c) 2014 Davide De Franceschi. All rights reserved.
//

import UIKit

enum FSM: Int {
	case LayoutA = 1
	case LayoutB = 2

	static func startingState() -> FSM {
		return LayoutA
	}
	static func allStates() -> [FSM] {
		return [LayoutA, LayoutB]
	}
	static func canMoveFromState(fromState: FSM, toState: FSM) -> Bool {
		switch (fromState, toState) {
		case (LayoutA, _):
			return true
		default:
			return false
		}
	}
}
class FSLVExample: FiniteStateLayoutView {
	override func nibName() -> String {
		return "NibTest"
	}

	override class func startingState() -> Int {
		return FSM.startingState().rawValue
	}
	override class func allStates() -> [Int] {
		return FSM.allStates().map { $0.rawValue }
	}
	override class func canMoveFromState(fromState: Int, toState: Int) -> Bool {
		switch (FSM(rawValue: fromState), FSM(rawValue: toState)) {
		case (.Some(let from), .Some(let to)):
			return FSM.canMoveFromState(from, toState: to)
		default:
			return false
		}
	}
	override func constraintsForState(state: Int) -> [NSLayoutConstraint]? {
		switch state {
		case 1:
			return layoutAConstraints
		case 2:
			return layoutBConstraints
		default:
			return nil
		}
	}

	@IBOutlet var layoutAConstraints: [NSLayoutConstraint]!
	@IBOutlet var layoutBConstraints: [NSLayoutConstraint]!
}

NibDesignable.swift

//
//  NibDesignable.swift
//
//  Copyright (c) 2014 Morten Bøgh
//
//  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

@IBDesignable
public class NibDesignable: UIView {

	// MARK: - Initializer
	override init(frame: CGRect) {
		super.init(frame: frame)
		self.setupNib()
	}

	// MARK: - NSCoding
	required public init(coder aDecoder: NSCoder) {
		super.init(coder: aDecoder)
		self.setupNib()
	}

	// MARK: - Nib loading

	/**
	Called in init(frame:) and init(aDecoder:) to load the nib and add it as a subview.
	*/
	private func setupNib() {
		var view = self.loadNib()
		view.frame = self.bounds
		view.autoresizingMask = .FlexibleWidth | .FlexibleHeight
		self.addSubview(view)
	}

	/**
	Called to load the nib in setupNib().

	:returns: UIView instance loaded from a nib file.
	*/
	public func loadNib() -> UIView {
		let bundle = NSBundle(forClass: self.dynamicType)
		let nib = UINib(nibName: self.nibName(), bundle: bundle)
		return nib.instantiateWithOwner(self, options: nil)[0] as UIView
	}

	/**
	Called in the default implementation of loadNib(). Default is class name.

	:returns: Name of a single view nib file.
	*/
	public func nibName() -> String {
		return self.dynamicType.description().componentsSeparatedByString(".").last!
	}
}