Allow providing a custom cache key which overrides the url in pin_setImage(from: URL?)

[MilesV64]

My server sends lots of signed URLs which means the PIN cache downloads new images every time since the signed URL is slightly different. I'd like to use a custom key that I pass in, and then the library would only use the URL for downloading the image, not for use as the cache key.

It could look like this:

// The latest signed url from my server
let myURL = self.imageURL 

// A string uniquing the image; if this changes then it means the image changed. 
// Otherwise it's the same image but could be a different URL due to signed URLs.
let id = self.imageID

// CacheKey would be optional so current library behavior is unchanged
// The library would then use the given id as the cache key, only using `myURL` if it needs to be downloaded
self.imageView.pin_setImage(from: myURL, cacheKey: id) 

Would this be possible? Is there any other way to get around handling lots of signed URLs without redownloading every time?

[garrettmoon]

Can you override imageFromCacheWithCacheKey?

PINRemoteImage/Source/Classes/include/PINRemoteImageManager.h

Lines 596 to 605 in 18637e4

	/**
	Returns the cacheKey for a given URL and processorKey. Exposed to be overridden if necessary or to be used with imageFromCacheWithCacheKey
	@see imageFromCacheWithCacheKey:completion:
	@param url NSURL that was used to download image
	@param processorKey An optional key to uniquely identify the processor used to post-process the downloaded image.
	@return returns an NSString which is the key used for caching.
	*/
	- (nonnull NSString *)cacheKeyForURL:(nonnull NSURL *)url processorKey:(nullable NSString *)processorKey;

[MilesV64]

Thank you for the reply, I think that should be enough to go on! I like the idea of setting the key at the same time as setting the URL because this override method requires additional state management/parsing of the URL (unless I'm missing a better way), but thank you for the suggestion.

To use this properly I would subclass PINRemoteImageManager correct? How would I then ensure that is being used instead of .shared() when calling pin_setImage() on a UIImageView?

[garrettmoon]

Yes, you'll need to override the class and then call setSharedImageManagerWithConfiguration: on the overridden class (since that method calls [self class] when instantiating the shared image manager, it'll correctly return your subclass when other places call PINRemoteImageManager.shared().

PINRemoteImage/Source/Classes/include/PINRemoteImageManager.h

Lines 219 to 225 in 18637e4

	/**
	Sets the shared instance of PINRemoteImageManager to an instance with the supplied configuration. If configuration is nil, [NSURLSessionConfiguration ephemeralSessionConfiguration] is used. You specify a custom configuration if you need to configure timeout values, cookie policies, additional HTTP headers, etc. This method should not be used if the shared instance has already been created.
	@param configuration The configuration used to create the PINRemoteImageManager.
	@note If you provide your own `sessionConfiguration`, please attention `HTTPMaximumConnectionsPerHost` property, it may causes timeout when in conjunction with `maxNumberOfConcurrentDownloads` if you set a larger number to `maxNumberOfConcurrentDownloads` but smaller number to `HTTPMaximumConnectionsPerHost`.
	*/
	+ (void)setSharedImageManagerWithConfiguration:(nullable NSURLSessionConfiguration *)configuration;

It's certainly not the most elegant solution and annoyingly has to be called before any parts of your code call the .shared() method, but it should work!

[MilesV64]

Really appreciate the quick responses, thank you! I think this is enough for me to go on, I do think something like what I mentioned in the issue would be pretty slick in the future but this should work!