CODEWITHSUNDEEP
iosswiftuitableviewcachingmemory-management
Jochen Österreicher
Jochen Österreicher

Reputation: 681

swift 3 iOS tableview datasource memory

I have a tableview which acts as a newsfeed. The cells are filled from an array of newsfeed items. I get the JSON from the Server, create newsfeed items from that input and attach them to my newsfeed array. a newsfeed item contains a title, a description and an imageurl string.

At:

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    var cell = tableView.dequeueReusableCell(withIdentifier: "ImageFeedItemTableViewCell1", for: indexPath) as! ImageFeedItemTableViewCell
    var item = self.feed!.items[indexPath.row]
    if (item.messageType == 1){
    cell = tableView.dequeueReusableCell(withIdentifier: "ImageFeedItemTableViewCell1", for: indexPath) as! ImageFeedItemTableViewCell
    cell.title.text = item.title
    cell.description.text = item.contentText

    if (item.imageURL as URL == URL(string: "noPicture")!)
    {
      cell.picture.image = UIImage(named:"empty")
    }
    else{

    if (item.cachedImage == UIImage(named:"default-placeholder")){
    let request = URLRequest(url: item.imageURL as URL)
    cell.picture.image = item.cachedImage
    cell.dataTask = self.urlSession.dataTask(with: request, completionHandler: { (data, response, error) -> Void in
        OperationQueue.main.addOperation({ () -> Void in
            if error == nil && data != nil {
                let image = UIImage(data: data!)
                if (image != nil){
              self.feed!.items[indexPath.row].cachedImage = image!
                }
                cell.picture.image = image


             }

        })

    }) 
        cell.dataTask?.resume()
    }else
    {
        cell.picture.image = item.cachedImage
    }
    }


}

the cells from the rows get filled with my newsfeeditem data.

But since i keep all my newsfeeditems inside an array, the memory usage is high and gehts higher for each additional newsfeeditem. I want it to work with endless scrolling like twitter, so i wonder how experienced developers tackle this memory issue.

Upvotes: 2

Views: 834

Answers (1)

Tj3n
Tj3n

Reputation: 9923

Your problem is in this lines or wherever you try to hold UIImage inside your array, this is really not advised and will cause crash due to memory since image is very large data and not advised to persist it in your RAM with UIImage inside array:

self.feed!.items[indexPath.row].cachedImage = image!

What you need to do is basically after fetch your image from URL, you save it to your app's documents folder and save the name or it's path that can distinct your image in cachedImage (just change the type to string or sth) and refetch it from your app's document folder when you need to show it in cellForRow

Flow: Fetch image -> save to disk and persist path in array -> refetch from disk with the path in cellForRow

Upvotes: 1

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