スクロールで浮き沈みする奴 Swift版

MovableFooter.swift

/**
* Copyright (c) 2014 pistatium
* 
* This software is released under the MIT License.
* 
* http://opensource.org/licenses/mit-license.php
*/

/*
* cf.
*   http://qiita.com/yimajo/items/34d6ba63e4eadfc8f421
*   https://github.com/sergio83/Movable-Footer/tree/1d2603e7e5efbc1b38e53b372c6ee9b046cd2cbd
*/

import Foundation
import UIKit

public class MovableFooterController : NSObject
{
    private let animationDuration = 0.22
    private var footerView:UIView
    private var scrollView:UIScrollView
    private var containerView:UIView
    private var beginScrollOffsetY:CGFloat = 0.0
    
    enum ScrollState {
        case Nutoral
        case InAnimation
    }
    private var scrollState = ScrollState.Nutoral
    
    init(footerView:UIView,scrollView:UIScrollView,containerView:UIView)
    {
        self.footerView = footerView
        self.scrollView = scrollView
        self.containerView = containerView
        super.init()
    }
    
    
    // MARK: - UIScrollViewDelegate
    //------------------------------------------------------------------------------------------------------------------------------------------
    public func scrollViewWillBeginDragging(scrollView: UIScrollView!)
    {
        self.beginScrollOffsetY = scrollView.contentOffset.y
    }
    
    
    public func scrollViewDidScroll(scrollView: UIScrollView!)
    {
        if ScrollState.InAnimation == scrollState {
            return
        }
        if (beginScrollOffsetY < scrollView.contentOffset.y && !footerView.hidden) {
            UIView.animateWithDuration(animationDuration,
                animations: {
                    self.scrollState = ScrollState.InAnimation
                    let rect = self.footerView.frame
                    self.footerView.frame = CGRectMake(
                        rect.origin.x,
                        rect.origin.y + rect.size.height,
                        rect.size.width,
                        rect.size.height
                    )
                }, completion: { finished in
                    self.footerView.hidden = true
                    self.scrollState = ScrollState.Nutoral
                }
            )
        } else if (scrollView.contentOffset.y < beginScrollOffsetY && footerView.hidden && 0.0 != beginScrollOffsetY) {
            self.footerView.hidden = false
            UIView.animateWithDuration(animationDuration,
                animations: {
                    self.scrollState = ScrollState.InAnimation
                    let rect = self.footerView.frame
                    self.footerView.frame = CGRectMake(
                        rect.origin.x,
                        rect.origin.y - rect.size.height,
                        rect.size.width,
                        rect.size.height
                    )
                }, completion: { finished in
                    self.scrollState = ScrollState.Nutoral
                    
                }
            )
            
        }

    }
}