[SDWebImage]

[leverdeterre]

Try to use an the previous cached image for placeholder

[bpoplauschi]

@leverdeterre could you please rebase this on top of master, so it's mergeable?

[Whirlwind]

I think it is not good idea.

The better way is that like setImageURL:placeHolderImage:UsingCache:. It like to request the network, and it will use cache if failed and the cache exists.

[bpoplauschi]

Replaced by 30f6726

[dreampiggy]

This API should be deprecated and it's not a good design.

Maybe your use case is that: if the memory or disk cache contains the image, show that instead of placeholder! else, firstly show the placeholder, then download from the network and replace the placeholder!. But this can be done by Core Animation's composition without this strange API.

If we can ensure all the process happend during the same runloop, even if you provide a placeholder and call imageView.image = placeholder
and then we query the cache synchronously, call imageView.image = image,
the actually rendering will only show the last image because the previous setImage will be ignored by Core Animation.

Of couse, if memory & disk cache missed. The placeholder will be rendering, and the network start, once finished, the imageView will trigger imageView.image = networkImage.

So, I think, all you need to do, it's a SDWebImageOptions for hint that the cache query should be synchronously, but not such a strange API. SD 4.3 introduce SDImageCacheQueryDiskSync and so this can be done easily. The current API will be marked deprecated and removed in 5.x.