collectionView.swift

//照片牆部分
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PropertyKeys.imageCell, for: indexPath) as! PostGridCollectionViewCell
        //將圖片透過data抓下來變成image再回傳給cell
        if let postImageURL = igposts[indexPath.item].node.thumbnail_src,
           let url = URL(string: postImageURL) {
            URLSession.shared.dataTask(with: url) { (data, response, error) in
                if let data = data {
                    DispatchQueue.main.async {
                        cell.postGridImageView.image = UIImage(data: data)
                    }
                }
            }.resume()
        }
        return cell
    }