SDWebImage implementation in parse using Swift - ios

Question

I am using parse to retrieve my images and labels and display it on a collection view. The problem was that the collection view loads all the images and labels at once making the load time long and memory usage was high. I was thinking that I would load 10 cells each time however I was recommended to use SDWebImage to make the app lighter. However I don't know how to implement it with parse using swift. I am suspecting that I would put some code in this piece of code below
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("newview", forIndexPath: indexPath) as! NewCollectionViewCell
let item = self.votes[indexPath.row]
let gesture = UITapGestureRecognizer(target: self, action: Selector("onDoubleTap:"))
gesture.numberOfTapsRequired = 2
cell.addGestureRecognizer(gesture)
// Display "initial" flag image
var initialThumbnail = UIImage(named: "question")
cell.postsImageView.image = initialThumbnail
// Display the country name
if let user = item["uploader"] as? PFUser{
item.fetchIfNeeded()
cell.userName!.text = user.username
var profileImgFile = user["profilePicture"] as! PFFile
cell.profileImageView.file = profileImgFile
cell.profileImageView.loadInBackground { image, error in
if error == nil {
cell.profileImageView.image = image
}
}
var sexInt = user["sex"] as! Int
var sex: NSString!
if sexInt == 0 {
sex = "M"
}else if sexInt == 1{
sex = "F"
}
var height = user["height"] as! Int
cell.heightSexLabel.text = "\(sex) \(height)cm"
}
if let votesValue = item["votes"] as? Int
{
cell.votesLabel?.text = "\(votesValue)"
}
// Fetch final flag image - if it exists
if let value = item["imageFile"] as? PFFile {
println("Value \(value)")
cell.postsImageView.file = value
cell.postsImageView.loadInBackground({ (image: UIImage?, error: NSError?) -> Void in
if error != nil {
cell.postsImageView.image = image
}
})
}
return cell
}
I have implemented SDWebImage using Pods and have imported through the Bridging Header. Is there anyone who knows how to implement SDWebImage with parse using Swift?

Answer 1

You should rethink your approach -
I believe you are using collectionViewDelegate method - collectionView(_:cellForItemAtIndexPath:)
this fires every time the collection view needs a view to handle.
In there you can access the cell imageView and set its image (For Example)-
cell.imageView.sd_setImageWithURL(url, placeholderImage:placeHolderImage, completed: { (image, error, cacheType, url) -> Void in })
And if you wish to fade in the image nicely, you could -
cell.imageView.sd_setImageWithURL(url, placeholderImage:placeHolderImage, completed: { (image, error, cacheType, url) -> Void in
if (cacheType == SDImageCacheType.None && image != nil) {
imageView.alpha = 0;
UIView.animateWithDuration(0.0, animations: { () -> Void in
imageView.alpha = 1
})
} else {
imageView.alpha = 1;
}
})
EDIT
I see the you use Parse, so you don't need SDWebImage, you need to use Parse - PFImageView, It will handle your background fetch for the image when it loads. You will need to save reference to your PFObject, but I believe you already do that.
For example (inside your cellForItemAtIndexPath)-
imageView.image = [UIImage imageNamed:#"..."]; // placeholder image
imageView.file = (PFFile *)someObject[#"picture"]; // remote image
[imageView loadInBackground];

Answer 2

How many objects are displaying in the collection view?
Since you mentioned SDWebImage, are you downloading the images in the background as well?
If you want to load the images as the user scrolls, have a look at the documentation for SDWebImage. The first use case describes how to display images in table view cells withouth blocking the main thread. The implementation for collection view cells should be similar.