Implementing an RxJava repository pattern that returns both the data and an error in a single stream
Is the following scenario possible in an RxJava stream for a repository pattern?
- Get data from an API if the cache (Room DB) has expired. Returns a Single.
- Save the remote data to the cache if there was a network call. Returns a Completable.
- The cache will be the single source of truth, so always load the data from the cache. Returns a Flowable.
- If there was an error at any point and the cache is empty, return the exception as is so the error can be displayed on the UI persistently.
- If there was an error at any point and the cache isn't empty, return the exception in a wrapper exception which will display a temporary error in a Snackbar. Then fallback to displaying the stale cache's data.
- This should allow me to display a loading panel while the download or cache load is happening, so I feel like it needs to be a single stream.
All of my attempts at this fail at the error reporting part, because the original exception can only be accessed in something like onErrorResumeNext where I can't return both an error and the list of data for the 5th point, since an error would stop the stream.
If the above is possible, would there also be a good way to prevent the 6th point from holding the user up if there was already a failed download previously?
e.g.
- Cache is stale, so there is a network call to download the data.
- Server is down and the request times out after 10 seconds.
- The cache is returned after 10 seconds with a Snackbar error.
- The user refreshes, and the server is still down so the cache is loaded after 10 seconds again.
Keeping the cache up-to-date isn't critical, so it would be preferred to hold off on checking the API again if it already failed once.
It feels like I may be missing something.
android caching repository-pattern rx-java2 android-room asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
add a comment |
Is the following scenario possible in an RxJava stream for a repository pattern?
- Get data from an API if the cache (Room DB) has expired. Returns a Single.
- Save the remote data to the cache if there was a network call. Returns a Completable.
- The cache will be the single source of truth, so always load the data from the cache. Returns a Flowable.
- If there was an error at any point and the cache is empty, return the exception as is so the error can be displayed on the UI persistently.
- If there was an error at any point and the cache isn't empty, return the exception in a wrapper exception which will display a temporary error in a Snackbar. Then fallback to displaying the stale cache's data.
- This should allow me to display a loading panel while the download or cache load is happening, so I feel like it needs to be a single stream.
All of my attempts at this fail at the error reporting part, because the original exception can only be accessed in something like onErrorResumeNext where I can't return both an error and the list of data for the 5th point, since an error would stop the stream.
If the above is possible, would there also be a good way to prevent the 6th point from holding the user up if there was already a failed download previously?
e.g.
- Cache is stale, so there is a network call to download the data.
- Server is down and the request times out after 10 seconds.
- The cache is returned after 10 seconds with a Snackbar error.
- The user refreshes, and the server is still down so the cache is loaded after 10 seconds again.
Keeping the cache up-to-date isn't critical, so it would be preferred to hold off on checking the API again if it already failed once.
It feels like I may be missing something.
android caching repository-pattern rx-java2 android-room asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
add a comment |
Is the following scenario possible in an RxJava stream for a repository pattern?
- Get data from an API if the cache (Room DB) has expired. Returns a Single.
- Save the remote data to the cache if there was a network call. Returns a Completable.
- The cache will be the single source of truth, so always load the data from the cache. Returns a Flowable.
- If there was an error at any point and the cache is empty, return the exception as is so the error can be displayed on the UI persistently.
- If there was an error at any point and the cache isn't empty, return the exception in a wrapper exception which will display a temporary error in a Snackbar. Then fallback to displaying the stale cache's data.
- This should allow me to display a loading panel while the download or cache load is happening, so I feel like it needs to be a single stream.
All of my attempts at this fail at the error reporting part, because the original exception can only be accessed in something like onErrorResumeNext where I can't return both an error and the list of data for the 5th point, since an error would stop the stream.
If the above is possible, would there also be a good way to prevent the 6th point from holding the user up if there was already a failed download previously?
e.g.
- Cache is stale, so there is a network call to download the data.
- Server is down and the request times out after 10 seconds.
- The cache is returned after 10 seconds with a Snackbar error.
- The user refreshes, and the server is still down so the cache is loaded after 10 seconds again.
Keeping the cache up-to-date isn't critical, so it would be preferred to hold off on checking the API again if it already failed once.
It feels like I may be missing something.
android caching repository-pattern rx-java2 android-room asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
Is the following scenario possible in an RxJava stream for a repository pattern?
- Get data from an API if the cache (Room DB) has expired. Returns a Single.
- Save the remote data to the cache if there was a network call. Returns a Completable.
- The cache will be the single source of truth, so always load the data from the cache. Returns a Flowable.
- If there was an error at any point and the cache is empty, return the exception as is so the error can be displayed on the UI persistently.
- If there was an error at any point and the cache isn't empty, return the exception in a wrapper exception which will display a temporary error in a Snackbar. Then fallback to displaying the stale cache's data.
- This should allow me to display a loading panel while the download or cache load is happening, so I feel like it needs to be a single stream.
All of my attempts at this fail at the error reporting part, because the original exception can only be accessed in something like onErrorResumeNext where I can't return both an error and the list of data for the 5th point, since an error would stop the stream.
If the above is possible, would there also be a good way to prevent the 6th point from holding the user up if there was already a failed download previously?
e.g.
- Cache is stale, so there is a network call to download the data.
- Server is down and the request times out after 10 seconds.
- The cache is returned after 10 seconds with a Snackbar error.
- The user refreshes, and the server is still down so the cache is loaded after 10 seconds again.
Keeping the cache up-to-date isn't critical, so it would be preferred to hold off on checking the API again if it already failed once.
It feels like I may be missing something.
android caching repository-pattern rx-java2 android-room android caching repository-pattern rx-java2 android-room asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
edited Nov 21 '18 at 7:53
peefartpoop
asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
asked Nov 21 '18 at 7:45
peefartpooppeefartpoop
84
84
add a comment |
add a comment |
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