エラー「Unexpectedly found nil while implicitly unwrapping an Optional value」について

UIPageViewControllerでのページ遷移の際に同時に動くタブを作成して、ビルドしようとしています。
イメージとしてはこちらのような感じです。

現状では
collectionView.datasource = self
のところでエラーが出てしまい、動作の確認ができていません。

解決法等お分かりになる方いらっしゃいましたら教えていただけますか。

Swift
1class PageViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate, UICollectionViewDelegateFlowLayout {
2 
3    
4    let pageList = ["first", "second", "third"]
5    
6    var collectionView:UICollectionView!
7    var page:Int = 0
8    let labelheight:CGFloat = 60
9    
10    required init?(coder aDecoder: NSCoder) {
11        super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
12    }
13    
14    override func viewDidLoad() {
15        super.viewDidLoad()
16        dataSource = self
17        delegate = self
18        setViewControllers([storyboardId(strID: "first") as! UIViewController], direction: .forward, animated: true, completion: nil)
19        
20        
21        
22        collectionView.dataSource = self   // ビルドするとここでエラーが起こってしまいます
23        collectionView.delegate = self
24        
25        // collectionViewレイアウト作成
26        CollectionViewLayoutSet()
27        
28        // collectionViewその他設定
29        collectionView.showsHorizontalScrollIndicator = false
30        collectionView.showsVerticalScrollIndicator = false
31        collectionView.delaysContentTouches = false
32        
33        view.addSubview(collectionView)
34        
35        self.view.subviews
36            .filter{ $0.isKind(of: UIScrollView.self) }
37            .forEach{($0 as! UIScrollView).delegate = self }
38    }
39    
40    
41    func storyboardId(strID: String) -> AnyObject! {
42        return (storyboard?.instantiateViewController(withIdentifier: strID))
43    }
44    
45    // 1ページ進む
46    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
47        let index = pageList.firstIndex(of: viewController.restorationIdentifier!)
48        if index! < (pageList.count - 1) {
49            return (storyboardId(strID: pageList[index! + 1]) as! UIViewController)
50        } else {
51            return nil
52        }
53    }
54    
55    
56    // 1ページ戻る
57    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
58        let index = pageList.firstIndex(of: viewController.restorationIdentifier!)
59        if 0 < index! {
60            return (storyboardId(strID: pageList[index! - 1]) as! UIViewController)
61        } else {
62            return nil
63        }
64    }
65    
66    // Page Controlを表示する
67    func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
68        return pageList.count
69    }
70    func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
71        return 0
72    }
73    
74    
75    
76    
77    func CollectionViewLayoutSet(){
78        let flowLayout = UICollectionViewFlowLayout()
79        flowLayout.minimumInteritemSpacing = 0.0
80        flowLayout.minimumLineSpacing = 0.0
81        flowLayout.scrollDirection = .horizontal
82        flowLayout.itemSize = CGSize(width:viewframewidth / 3 ,  height:CGFloat(labelheight))
83        let rec = CGRect(x: 0.0, y:statusBarHeight , width:viewframewidth , height: labelheight)
84        collectionView = UICollectionView(frame: rec, collectionViewLayout: flowLayout)
85    }
86}
87
88extension PageViewController: UICollectionViewDelegate, UICollectionViewDataSource {
89    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
90        return pageList.count
91    }
92    
93    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
94        collectionView.register(cellType:tab.self)
95        let cell: tab = collectionView.dequeueReusableCell(with: tab.self, for: indexPath)
96        cell.Set(Text: pageList[indexPath.row])
97        return cell
98    }
99    
100    
101}
102
103extension PageViewController {
104    func scrollViewDidScroll(_ scrollView: UIScrollView) {
105        if(scrollView.className == "UICollectionView"){
106            return
107        }
108        
109        let LeftRightJug = viewframewidth - scrollView.contentOffset.x
110        if(LeftRightJug == 0){
111            return
112        }
113        let Move = scrollView.contentOffset.x / 3
114        let first:Int = LeftRightJug > 0 ? 1 : 0
115        let End:Int = LeftRightJug > 0 ? (pageList.count - 1) : (pageList.count - 2)
116        if(first < page && page < End) {
117            let pageWidth = CGFloat(page - 2) * viewframewidth
118            let TabPageWidth = pageWidth / 3
119            
120            collectionView.contentOffset = CGPoint(x: Move + TabPageWidth, y:0)
121        }
122    }
123}
124
125