AlamofireImage Collection cell puts image in AutoPurgingImageCache after download

Question

I have a custom UICollectionViewCell that gets an image with AlamofireImage (2.4). It downloads OK, but it doesn't seem to be putting in the cache.

I have a swift file with my global cache.

import Foundation
import Alamofire
import AlamofireImage

// AlamofireImage cache with 30 MB cache
let imageCache = AutoPurgingImageCache(
    memoryCapacity: 30 * 1024 * 1024,
    preferredMemoryUsageAfterPurge: 20 * 1024 * 1024
)

The collection cell looks like this. It downloads the image with af_setImageWithURL and in the callback puts this image in the global cache after it sets it on the cell.

import UIKit
import Alamofire
import AlamofireImage

    class MyCatCell: UICollectionViewCell {

    @IBOutlet weak var fancyImage: UIImageView!

    var imageURL: String?

    func configureCell(uri: String?) {
        imageURL = uri
        resetCell()
        loadImage()
    }

    func resetCell() {
        fancyImage.af_cancelImageRequest()
        fancyImage.image = nil
    }

    func loadImage() {
        guard imageURL != nil else {
            return
        }
        if let image = imageCache.imageWithIdentifier(imageURL!) {
            // set image from cache
            print("image from cache")
            fancyImage.image = image
        } else {
            // get image and cache it
            let url = NSURL(string: imageURL!)!
            fancyImage.af_setImageWithURL(
                url,
                placeholderImage: nil,
                filter: nil,
                imageTransition: .CrossDissolve(0.5),
                completion: { response in
                    if response.result.isSuccess {
                        print("response.result.isSuccess \(self.imageURL!)")
                        // store this in the image cache
                        imageCache.addImage(response.result.value!, withIdentifier: self.imageURL!)
                    }
                }
            )
        }
    }
}

The images sets in the cell, the print("response.result.isSuccess \(self.imageURL!)") fires (so the call back is running), but the print("image from cache") never fires. imageCache.imageWithIdentifier(imageURL!) is always nil. It just downloads the image again when I load this cell again using the same URL. Any idea why this isn't working?

I fixed this issue. I made the cache too small for the images that were being downloaded, so the cache was purging before I could get the reuse the image. To check the size of memory your cache is using, use **imageCache.memoryUsage**. — skymook, Jul 14 '16 at 08:27

score 1 · Accepted Answer · answered Nov 28 '16 at 15:33

I found that I only needed to make the size of the cache larger. The images I was downloading were bigger than I predicted, and the cache was filling up far too quickly, then purging.

// AlamofireImage cache with 60 MB cache
let imageCache = AutoPurgingImageCache(
    memoryCapacity: 60 * 1024 * 1024,
    preferredMemoryUsageAfterPurge: 20 * 1024 * 1024
)

You can see your cache filling up if you periodically use imageCache.memoryUsage.

Print('Image cache size = \(imageCache.memoryUsage)')

AlamofireImage Collection cell puts image in AutoPurgingImageCache after download

1 Answers1