URLSession cache only
Sometimes I want to get data from the cache only when using URLSession. For example when quickly scrolling in a UITableView, I would like to show images that are already in the cache, but do not fire any HTTP requests. Images are just an example could be anything.
So I'm currently looking into URLSession's CachePolicy but it doesn't support an option to only get valid (not expired, etc) data from cache.
I can look into the URLCache myself, but this also of course returns data that might be expired. Is there some API that can validate a CachedURLResponse? Because then I can do it myself. Or do I have to implement the validating myself.
swift nsurlsession foundation
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
|
show 1 more comment
Sometimes I want to get data from the cache only when using URLSession. For example when quickly scrolling in a UITableView, I would like to show images that are already in the cache, but do not fire any HTTP requests. Images are just an example could be anything.
So I'm currently looking into URLSession's CachePolicy but it doesn't support an option to only get valid (not expired, etc) data from cache.
I can look into the URLCache myself, but this also of course returns data that might be expired. Is there some API that can validate a CachedURLResponse? Because then I can do it myself. Or do I have to implement the validating myself.
swift nsurlsession foundation
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
2
For Image Cache use SDWemImage Library
– Manish Mahajan
Nov 21 '18 at 9:23
@ManishMahajan Images are an example could be really anything.
– Haagenti
Nov 21 '18 at 9:45
@inokey I think this is not a duplicate to the link you provided. I have added Images as an example for a HTTP request. Could be really anything. Also in the link he uses an extra Dictionary to have them in memory. I would like to avoid this as URLSession already does this in URLCache.
– Haagenti
Nov 21 '18 at 9:47
@Haagenti try looking into 304 http status code. I remember I used it to determine whether or not I should get stuff from cache. Unfortunately I can't remember more specific.
– inokey
Nov 21 '18 at 9:50
@inokey Mmm not sure if 304 status code will do the trick because in the cache just contains the original response which will most likely be a 200 response.
– Haagenti
Nov 21 '18 at 15:33
|
show 1 more comment
Sometimes I want to get data from the cache only when using URLSession. For example when quickly scrolling in a UITableView, I would like to show images that are already in the cache, but do not fire any HTTP requests. Images are just an example could be anything.
So I'm currently looking into URLSession's CachePolicy but it doesn't support an option to only get valid (not expired, etc) data from cache.
I can look into the URLCache myself, but this also of course returns data that might be expired. Is there some API that can validate a CachedURLResponse? Because then I can do it myself. Or do I have to implement the validating myself.
swift nsurlsession foundation
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
Sometimes I want to get data from the cache only when using URLSession. For example when quickly scrolling in a UITableView, I would like to show images that are already in the cache, but do not fire any HTTP requests. Images are just an example could be anything.
So I'm currently looking into URLSession's CachePolicy but it doesn't support an option to only get valid (not expired, etc) data from cache.
I can look into the URLCache myself, but this also of course returns data that might be expired. Is there some API that can validate a CachedURLResponse? Because then I can do it myself. Or do I have to implement the validating myself.
swift nsurlsession foundation
swift nsurlsession foundation
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
edited Nov 21 '18 at 11:31
ayaio
58.4k20132189
58.4k20132189
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
asked Nov 21 '18 at 9:13
HaagentiHaagenti
4,15032745
4,15032745
2
For Image Cache use SDWemImage Library
– Manish Mahajan
Nov 21 '18 at 9:23
@ManishMahajan Images are an example could be really anything.
– Haagenti
Nov 21 '18 at 9:45
@inokey I think this is not a duplicate to the link you provided. I have added Images as an example for a HTTP request. Could be really anything. Also in the link he uses an extra Dictionary to have them in memory. I would like to avoid this as URLSession already does this in URLCache.
– Haagenti
Nov 21 '18 at 9:47
@Haagenti try looking into 304 http status code. I remember I used it to determine whether or not I should get stuff from cache. Unfortunately I can't remember more specific.
– inokey
Nov 21 '18 at 9:50
@inokey Mmm not sure if 304 status code will do the trick because in the cache just contains the original response which will most likely be a 200 response.
– Haagenti
Nov 21 '18 at 15:33
|
show 1 more comment
2
For Image Cache use SDWemImage Library
– Manish Mahajan
Nov 21 '18 at 9:23
@ManishMahajan Images are an example could be really anything.
– Haagenti
Nov 21 '18 at 9:45
@inokey I think this is not a duplicate to the link you provided. I have added Images as an example for a HTTP request. Could be really anything. Also in the link he uses an extra Dictionary to have them in memory. I would like to avoid this as URLSession already does this in URLCache.
– Haagenti
Nov 21 '18 at 9:47
@Haagenti try looking into 304 http status code. I remember I used it to determine whether or not I should get stuff from cache. Unfortunately I can't remember more specific.
– inokey
Nov 21 '18 at 9:50
@inokey Mmm not sure if 304 status code will do the trick because in the cache just contains the original response which will most likely be a 200 response.
– Haagenti
Nov 21 '18 at 15:33
2
2
For Image Cache use SDWemImage Library
– Manish Mahajan
Nov 21 '18 at 9:23
For Image Cache use SDWemImage Library
– Manish Mahajan
Nov 21 '18 at 9:23
@ManishMahajan Images are an example could be really anything.
– Haagenti
Nov 21 '18 at 9:45
@ManishMahajan Images are an example could be really anything.
– Haagenti
Nov 21 '18 at 9:45
@inokey I think this is not a duplicate to the link you provided. I have added Images as an example for a HTTP request. Could be really anything. Also in the link he uses an extra Dictionary to have them in memory. I would like to avoid this as URLSession already does this in URLCache.
– Haagenti
Nov 21 '18 at 9:47
@inokey I think this is not a duplicate to the link you provided. I have added Images as an example for a HTTP request. Could be really anything. Also in the link he uses an extra Dictionary to have them in memory. I would like to avoid this as URLSession already does this in URLCache.
– Haagenti
Nov 21 '18 at 9:47
@Haagenti try looking into 304 http status code. I remember I used it to determine whether or not I should get stuff from cache. Unfortunately I can't remember more specific.
– inokey
Nov 21 '18 at 9:50
@Haagenti try looking into 304 http status code. I remember I used it to determine whether or not I should get stuff from cache. Unfortunately I can't remember more specific.
– inokey
Nov 21 '18 at 9:50
@inokey Mmm not sure if 304 status code will do the trick because in the cache just contains the original response which will most likely be a 200 response.
– Haagenti
Nov 21 '18 at 15:33
@inokey Mmm not sure if 304 status code will do the trick because in the cache just contains the original response which will most likely be a 200 response.
– Haagenti
Nov 21 '18 at 15:33
|
show 1 more comment
1 Answer
1
active
oldest
votes
That's a fairly unusual request. Normally, you're either writing code to operate in an offline mode (in which case you want to pull from the cache whether the cached results are still valid or not) or you are online (in which case you want to fetch new data if it isn't valid).
I would encourage you to really think long and hard about whether you really want to force cache validation if you aren't firing network requests.
That said, if you really want that behavior, there are two ways you can do it:
- Use
NSURLRequestReturnCacheDataDontLoadand validate the age of the cached response yourself. - Perform the request in a custom session, use
NSURLRequestUseProtocolCachePolicy, and in that session, install a customNSURLProtocolsubclass that overridesinitWithTask:cachedResponse:client:andstartLoading, and callsURLProtocol:didFailWithError:on the provided client at the top of itsstartLoadingmethod.
The second approach is probably the best option, because you don't have to worry about knowing all the esoteric rules for cache validation. By making the actual load fail, the cache will work normally, but as soon as it actually would start making a network request, your custom protocol prevents that from happening. And because you'll register the protocol only in that specific session (via the protocolClasses array on the session configuration), it won't break networking in other sessions.
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
add a comment |
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That's a fairly unusual request. Normally, you're either writing code to operate in an offline mode (in which case you want to pull from the cache whether the cached results are still valid or not) or you are online (in which case you want to fetch new data if it isn't valid).
I would encourage you to really think long and hard about whether you really want to force cache validation if you aren't firing network requests.
That said, if you really want that behavior, there are two ways you can do it:
- Use
NSURLRequestReturnCacheDataDontLoadand validate the age of the cached response yourself. - Perform the request in a custom session, use
NSURLRequestUseProtocolCachePolicy, and in that session, install a customNSURLProtocolsubclass that overridesinitWithTask:cachedResponse:client:andstartLoading, and callsURLProtocol:didFailWithError:on the provided client at the top of itsstartLoadingmethod.
The second approach is probably the best option, because you don't have to worry about knowing all the esoteric rules for cache validation. By making the actual load fail, the cache will work normally, but as soon as it actually would start making a network request, your custom protocol prevents that from happening. And because you'll register the protocol only in that specific session (via the protocolClasses array on the session configuration), it won't break networking in other sessions.
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
add a comment |
That's a fairly unusual request. Normally, you're either writing code to operate in an offline mode (in which case you want to pull from the cache whether the cached results are still valid or not) or you are online (in which case you want to fetch new data if it isn't valid).
I would encourage you to really think long and hard about whether you really want to force cache validation if you aren't firing network requests.
That said, if you really want that behavior, there are two ways you can do it:
- Use
NSURLRequestReturnCacheDataDontLoadand validate the age of the cached response yourself. - Perform the request in a custom session, use
NSURLRequestUseProtocolCachePolicy, and in that session, install a customNSURLProtocolsubclass that overridesinitWithTask:cachedResponse:client:andstartLoading, and callsURLProtocol:didFailWithError:on the provided client at the top of itsstartLoadingmethod.
The second approach is probably the best option, because you don't have to worry about knowing all the esoteric rules for cache validation. By making the actual load fail, the cache will work normally, but as soon as it actually would start making a network request, your custom protocol prevents that from happening. And because you'll register the protocol only in that specific session (via the protocolClasses array on the session configuration), it won't break networking in other sessions.
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
add a comment |
That's a fairly unusual request. Normally, you're either writing code to operate in an offline mode (in which case you want to pull from the cache whether the cached results are still valid or not) or you are online (in which case you want to fetch new data if it isn't valid).
I would encourage you to really think long and hard about whether you really want to force cache validation if you aren't firing network requests.
That said, if you really want that behavior, there are two ways you can do it:
- Use
NSURLRequestReturnCacheDataDontLoadand validate the age of the cached response yourself. - Perform the request in a custom session, use
NSURLRequestUseProtocolCachePolicy, and in that session, install a customNSURLProtocolsubclass that overridesinitWithTask:cachedResponse:client:andstartLoading, and callsURLProtocol:didFailWithError:on the provided client at the top of itsstartLoadingmethod.
The second approach is probably the best option, because you don't have to worry about knowing all the esoteric rules for cache validation. By making the actual load fail, the cache will work normally, but as soon as it actually would start making a network request, your custom protocol prevents that from happening. And because you'll register the protocol only in that specific session (via the protocolClasses array on the session configuration), it won't break networking in other sessions.
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
That's a fairly unusual request. Normally, you're either writing code to operate in an offline mode (in which case you want to pull from the cache whether the cached results are still valid or not) or you are online (in which case you want to fetch new data if it isn't valid).
I would encourage you to really think long and hard about whether you really want to force cache validation if you aren't firing network requests.
That said, if you really want that behavior, there are two ways you can do it:
- Use
NSURLRequestReturnCacheDataDontLoadand validate the age of the cached response yourself. - Perform the request in a custom session, use
NSURLRequestUseProtocolCachePolicy, and in that session, install a customNSURLProtocolsubclass that overridesinitWithTask:cachedResponse:client:andstartLoading, and callsURLProtocol:didFailWithError:on the provided client at the top of itsstartLoadingmethod.
The second approach is probably the best option, because you don't have to worry about knowing all the esoteric rules for cache validation. By making the actual load fail, the cache will work normally, but as soon as it actually would start making a network request, your custom protocol prevents that from happening. And because you'll register the protocol only in that specific session (via the protocolClasses array on the session configuration), it won't break networking in other sessions.
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
edited Dec 3 '18 at 4:56
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
answered Dec 2 '18 at 5:09
dgatwooddgatwood
8,16012044
8,16012044
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
add a comment |
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
NSURLRequestReturnCacheDataDontLoad : "Use existing cache data, regardless or age or expiration date, and fail if no cached data is available". I would like only data when its valid.
– Haagenti
Dec 2 '18 at 21:05
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Ah. I misread your question. I'll update my answer.
– dgatwood
Dec 3 '18 at 4:44
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
Updated. The custom protocol approach is slightly more complex, but still a lot simpler than cache validation. :-)
– dgatwood
Dec 3 '18 at 4:57
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
I will implement your second approach which also sounds to me like the best option. Thank you.
– Haagenti
Dec 3 '18 at 6:55
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
You might find that this ends up working the same way as pulling everything from the cache. If so, then the only option is #1.
– dgatwood
Dec 3 '18 at 18:40
add a comment |
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2
For Image Cache use SDWemImage Library
– Manish Mahajan
Nov 21 '18 at 9:23
@ManishMahajan Images are an example could be really anything.
– Haagenti
Nov 21 '18 at 9:45
@inokey I think this is not a duplicate to the link you provided. I have added Images as an example for a HTTP request. Could be really anything. Also in the link he uses an extra Dictionary to have them in memory. I would like to avoid this as URLSession already does this in URLCache.
– Haagenti
Nov 21 '18 at 9:47
@Haagenti try looking into 304 http status code. I remember I used it to determine whether or not I should get stuff from cache. Unfortunately I can't remember more specific.
– inokey
Nov 21 '18 at 9:50
@inokey Mmm not sure if 304 status code will do the trick because in the cache just contains the original response which will most likely be a 200 response.
– Haagenti
Nov 21 '18 at 15:33