React-native-fast-image: Add way to check if an image is cached.

[jslok]

I want to load a low quality image if user is on mobile data. However, if the high quality image is already cached, then show the high quality image. Any way to find out if a particular image is cached already or not?

[DylanVann]

It would be a new feature.

We could add something like: FastImage.isCached(url).then(res => ...)

Another potential feature that could solve this would be something like a cache only mode.

[padupuy]

@DylanVann it will be very useful, especially with a fading transition when the image is loaded.
Currently, the fading transition is always applied, if we can check if the image is in the cache, we could apply the transition only the first time.

[erickreutz]

Any work being done towards this?