Swift : Firestore와 collectionView를 사용하여 게시 목록 검색, 업데이트 및 삭제 처리

코드

import FirebaseFirestore

class ViewController: UIViewController {

 @IBOutlet weak var collectionView: UICollectionView!
 var stories: [Story] = []
 let db = Firestore.firestore()
 var storiesListener: ListenerRegistration?

 override func viewDidLoad() {
        super.viewDidLoad()
        self.setStoriesListener()
    }

func setStoriesListener() {
        self.storiesListener = self.db.collection("stories")
            .order(by: "createTime", descending: true)  // 降順で（日付が新しい順から）取ってくる
            .addSnapshotListener({ (querySnapshot, error) in
                guard let snapshot = querySnapshot else {
                    print("Error while getting collection: \(error)")
                    return
                }
                snapshot.documentChanges.forEach { diff in
                    if (diff.type == .added) {
                        let story = Story(document: diff.document)
                        let newIndex = Int(diff.newIndex)
                        self.stories.insert(story, at: newIndex) // 投稿を格納している配列のindexとFirestore上のindexを揃えてやる
                        self.collectionView.insertItems(at: [IndexPath(item: newIndex, section: 0)])
                    }
                    if (diff.type == .modified) {
                        // いいねやコメントなどのフィールドバリューの更新はここが呼ばれる
                        // リアルタイムでいいね数やコメント数の変化を反映したい場合は collectionView.reloadItems(at:)を使うはず
                    }
                    if (diff.type == .removed) {
                        let oldIndex = Int(diff.oldIndex)
                        self.stories.remove(at: oldIndex)
                        self.collectionView.deleteItems(at: [IndexPath(item: oldIndex, section: 0)])
                    }
                }

            })
｝

extension ViewController: UICollectionViewDataSource, UICollectionViewDelegate {

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.stories.count
   }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! StoryCell
        let story = self.stories[indexPath.row] 
        // cellに画像やラベルテキストを設定する処理           
        return cell
    }       
}

리스너를 설정하는 타이밍

reloadData()와 insertItem(at: Index)의 차이

reloadData () 그럼 왜 안돼?

참고한 기사