Using cache key to load image with ui image view

[ElrB]

Hi Guys,

I am using kingfisher in a messaging app, and I would like to know how to load images with ui image view (not to retrieve) using a cache key. So this is what happens:

1. Current user sends a photo image message, and this image is manually cached immediately using a specific chat message cache and cache key.
2. The collection view is reloaded to show the message, and right now I use the cache.retrieveImage, then set it in completion block, and as result this causes a few issues, such as image flickering and slight delay in showing image, as images are stored to disk.

I want to load image onto image view using cache key, so that I can make use of .keepCurrentImageWhileLoading, .loadDiskFileSynchronously.

I cannot use url as image is not downloaded. I saw that there is a way to use a LocalFileImageDataProvider, but in this case the image a stored using kingfisher.

Thanks.

[ElrB]

My current work around:
Since kingfisher promises to use absolute string from url to check if image is cached, I simply create URL(string: "cache key") then pass it in setImage method as url (that way I get to use setImage options input param). Of course this caused me to force unwrap url, but I first check if image is cached.

[onevcat]

You can create an image resource with a customized cache key and load it:

let resource = KF.ImageResource(downloadURL: url, cacheKey: "my_cache_key")
imageView.kf.setImage(with: resource)

[ElrB]

The thing is, the images are not being downloaded in the first place, but manually cache them, then try to set them onto image view through imageView.kf.setImage. As you know setImage does not take cache key, that I used to cache the image. I tried using KF.ImageResource but I don't have a url for the image, and I think the resource here is used to download and cache image under specific key. All in all, just note that I am not downloading the images but trying to use imageView.kf.setImage in order to take advantage of the options param.

[onevcat]

If there is already a place to load the image (and you will always have it locally), then maybe instead of the ImageResource (which is basically for remote image), you can use one of the ImageDataProvider to provide the image. Then, Kingfisher will handle the left.

Check this for detail: https://github.com/onevcat/Kingfisher/wiki/Cheat-Sheet#imagedataprovider

Or as long as you can get the raw data of the image somewhere, you can also create your own data provider.

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If you only have the local image transiently, and in the future there might be a chance you need to load it from a remote URL, then you can firstly manually cache it in the ImageCache with a cache key, then create an ImageResource to load it, from cache first, and if not found, download from the remote URL.

[ElrB]

Is there an ImageDataProvider to load an image from kingfisher cache? If yes, kindly comment. I only know of LocalFileImageDataProvider, which loads from app files.