[aerogear-dev] [aerogear-android] DataManager API inconsistency + solution

[Tadeas Kriz]

On 08 Jan 2014, at 15:30, Summers Pittman <supittma at redhat.com> wrote:

> On 01/08/2014 05:51 AM, Tadeas Kriz wrote:
>> Hey everyone,
>> 
>> I’ve been recently going through the DataManager API in aerogear-android. In this email, I’d like to suggest addiction of two method (or possibly three) into the `Store<T>` interface. These would be:
>> 
>> ```java
>> /**
>>  * If store is open, it can be read or written to.
>>  */
>> boolean isOpen();
>> 
>> /**
>>  * Opens store in current thread (blocking).
>>  */
>> Store<T> open();
>> 
>> /**
>>  * Opens store in background thread and then callback#onSuccess is called.
>>  */
>> void open(Callback<Store<T>> callback);
>> ```
> I think those are fine. Feel free to JIRA it up and Passos and I will 
> review.
>> 
>>> From my point of view, this makes sense to be in the `Store<T>` so I can switch between stores easily during development with no need to change other code. Also, if `read` or `write` operations are done with closed store, there are two possible workflows. First one is, that I’d fail and throw an exception. Second (and for me a preferred one) is, that all those methods would internally check if the store is open and if not, they’d call the `open` method. This also leads me to another API change for `Store<T>`.
>> 
>> ```java
>> /**
>>  * Reads all the data from the underlying storage system asynchronously.
>>  */
>> void readAll(Callback<Collection<T>> callback);
>> 
>> /**
>>  * Reads a specific object/record from the underlying storage system asynchronously.
>>  */
>> void read(Serializable id, Callback<T> callback);
>> 
>> /**
>>  * Search for objects/records from the underlying storage system asynchronously.
>>  */
>> void readWithFilter(ReadFilter filter, Callback<List<T>> callback);
>> 
>> /**
>>  * Saves the given object in the underlying storage system asynchronously.
>>  */
>> void save(T item, Callback<Void> callback);
>> 
>> /**
>>  * Resets the entire storage system asynchronously.
>>  */
>> void reset(Callback<Void> callback);
>> 
>> /**
>>  * Removes a specific object/record from the underlying storage system asynchronously.
>>  */
>> void remove(Serializable id, Callback<Void> callback);
>> 
>> /**
>>  * Checks if the storage system contains no stored elements asynchronously.
>>  */
>> void isEmpty(Callback<Boolean> callback);
>> ```
>> 
>> That’s right, async methods for easy access to the storage from background thread, without the pain of writing it myself (for example, it makes no sense if I want to just call `store.save(..)` and I’d have to write all the `AsyncTask` boilerplate).
>> 
>> So, what do you think?
> 
> I would rather throw an exception than open a database when you call 
> read and friends. That way a developer doesn't accidentally open a 
> database he meant to be closed. I don't have that strong of a feeling on 
> that point one way or another however.

That’s right, it’s probably less error prone in scenarios when you want the store closed.

> 
> My stronger feeling is on adding callbacks to the stores methods. I 
> prefer for the Store to be synchronous and Pipes to be asynchronous. We 
> could add a StorePipe to our PypeTipes which may solve some of the headache.
> 

Would “void open(Callback<Store<T>> callback);” make sense then? I mean, that would add another inconsistency in the API, as one method would be async and the rest would be only synchronous, wouldn’t it?

> Passos, wdyt?
> 
> 
>> 
>> PS: You can find the whole text with highlighted syntax here:
>> 
>> —
>> Tadeas Kriz
>> tkriz at redhat.com
>> 
>> 
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>> aerogear-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/aerogear-dev
> 
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