StorIOContentResolver.md

StorIOContentResolver — API for Content Resolver

Important notice: All StorIO APIs looks same, if you know how to work with StorIOSQLite -> you know how to work with StorIOContentResolver!

0. Create an instance of StorIOContentResolver

StorIOContentResolver storIOContentResolver = DefaultStorIOContentResolver.builder()
  .contentResolver(yourContentResolver)
  .addTypeMapping(SomeType.class, typeMapping) // required for object mapping
  .build();

It's a good practice to use one instance of StorIOContentResolver per application, but it's not required.

1. Get Operation

Get list of objects with blocking call:

final List<Tweet> tweets = storIOContentResolver
  .get()
  .listOfObjects(Tweet.class)
  .withQuery(Query.builder()
    .uri(someUri)
    .where("author = ?")
    .whereArgs("@artem_zin")
    .build())
  .prepare()
  .executeAsBlocking();

Get Cursor via blocking call:

final Cursor tweetsCursor = storIOContentResolver
  .get()
  .cursor()
  .withQuery(Query.builder()
    .uri(someUri)
    .where("author = ?")
    .whereArgs("@artem_zin")
    .build())
  .prepare()
  .executeAsBlocking();

Things become much more interesting with RxJava!

What if you want to observe changes in StorIOContentResolver?

First-case: Receive updates to Flowable on each change of Uri from Query

storIOContentResolver
  .get()
  .listOfObjects(Tweet.class)
  .withQuery(Query.builder()
    .uri(tweetsUri)
    .where("author = ?")
    .whereArgs("@artem_zin")
    .build())
  .prepare()
  .asRxFlowable(BackpressureStrategy.LATEST) // Get Result as io.reactivex.Flowable and subscribe to further updates of Uri from Query!
  .observeOn(mainThread()) // All Rx operations work on Schedulers.io()
  .subscribe(tweets -> { // Please don't forget to unsubscribe
      // will be called with first result and then after each change of Uri from Query
      adapter.setData(tweets);
    }
  );
// don't forget to manage Subscription and unsubscribe in lifecycle methods to prevent memory leaks

Second case: Handle changes manually

storIOContentResolver
  .observeChangesOfUri(someUri)
  .subscribe(changes -> { // Just subscribe or apply Rx Operators such as Debounce, Filter, etc
    // do what you want!
  });

Get result via Rx only once and ignore further changes

storIOContentResolver
  .get()
  .listOfObjects(Tweet.class)
  .withQuery(Query.builder()
          .uri(tweetsUri)
          .build())
  .prepare()
  .asRxFlowable(BackpressureStrategy.LATEST)
  .take(1) // To get result only once and ignore further changes of this Uri
  .observeOn(mainThread())
  .subscribe(tweets -> {
      // Display data
    }
  );

Customize behavior of Get Operation with GetResolver

GetResolver<Type> getResolver = new DefaultGetResolver()<Type> {
  @Override @NonNull public SomeType mapFromCursor(@NonNull Cursor cursor) {
    return new SomeType(); // parse Cursor here
  }
};

storIOContentResolver
  .get()
  .listOfObjects(Tweet.class)
  .withQuery(someQuery)
  .withGetResolver(getResolver) // here we set custom GetResolver for Get Operation
  .prepare()
  .executeAsBlocking();

Several things about Get Operation:

• There is DefaultGetResolver — Default implementation of GetResolver which simply redirects query to StorIOContentResolver, in 99% of cases DefaultGetResolver will be enough
• As you can see, results of Get Operation computed even if you'll apply RxJava operators such as Debounce, if you want to avoid unneeded computations, please combine StorIOContentResolver.observeChangesOfUri() with Get Operation manually.
• In next versions of StorIO we are going to add Lazy<T> to allow you skip unneeded computations

2. Put Operation

Put object of some type

Tweet tweet = getSomeTweet();

storIOContentResolver
  .put()
  .object(tweet)
  .prepare()
  .executeAsBlocking(); // or asRxSingle()

Put multiple objects of some type

List<Tweet> tweets = getSomeTweets();

storIOContentResolver
  .put()
  .objects(tweets)
  .prepare()
  .executeAsBlocking(); // or asRxSingle()

Put ContentValues

ContentValues contentValues = getSomeContentValues(); 

storIOContentResolver
  .put()
  .contentValues(contentValues)
  .withPutResolver(putResolver) // requires PutResolver<ContentValues>
  .prepare()
  .executeAsBlocking(); // or asRxSingle()

Put Operation requires PutResolver which defines the behavior of Put Operation (insert or update).

PutResolver<SomeType> putResolver = new DefaultPutResolver<SomeType>() {
  @Override @NonNull public InsertQuery mapToInsertQuery(@NonNull SomeType object) {
    return InsertQuery.builder()
      .uri("content://some_uri")
      .build();
  }
  
  @Override @NonNull public UpdateQuery mapToUpdateQuery(@NonNull SomeType object) {
    return UpdateQuery.builder()
      .uri("content://some_uri")
      .where("some_column = ?")
      .whereArgs(object.someColumn())
      .build();
  }
  
  @Override @NonNull public ContentValues mapToContentValues(@NonNull SomeType object) {
    final ContentValues contentValues = new ContentValues();
    // fill with fields from object
    return contentValues;
  }
};

Several things about Put Operation:

• Put Operation requires PutResolver
• Result of Put Operation can be useful if you want to know what happened: insert (and insertedId) or update (and number of updated rows)

3. Delete Operation

Delete object

Tweet tweet = getSomeTweet();

storIOContentResolver
  .delete()
  .object(tweet)
  .prepare()
  .executeAsBlocking(); // or asRxCompletable()

Delete multiple objects

List<Tweet> tweets = getSomeTweets();

storIOContentResolver
  .delete()
  .objects(tweets)
  .prepare()
  .executeAsBlocking(); // or asRxCompletable()

Delete Resolver

DeleteResolver<SomeType> deleteResolver = new DefaultDeleteResolver<SomeType>() {
  @Override @NonNull public DeleteQuery mapToDeleteQuery(@NonNull SomeType object) {
    return DeleteQuery.builder()
      .uri("content://some_uri")
      .where("some_column = ?")
      .whereArgs(object.someColumn())
      .build();
  }
};

Several things about Delete Operation:

• Result of Delete Operation can be useful if you want to know what happened

How object mapping works?

You can set default type mappings when you build instance of StorIOContentResolver

StorIOContentResolver storIOContentResolver = DefaultStorIOContentResolver.builder()
  .contentResolver(yourContentResolver)
  .addTypeMapping(Tweet.class, ContentResolverTypeMapping.<Tweet>builder()
    .putResolver(new TweetPutResolver()) // object that knows how to perform Put Operation (insert or update)
    .getResolver(new TweetGetResolver()) // object that knows how to perform Get Operation
    .deleteResolver(new TweetDeleteResolver())  // object that knows how to perform Delete Operation
    .build())
  .addTypeMapping(...)
  // other options
  .build(); // This instance of StorIOContentResolver will know how to work with Tweet objects

You can override Operation Resolver per each individual Operation.

Few tips about Operation Resolvers:

• If your entities are immutable or they have builders or they use AutoValue/AutoParcel -> write your own Operation Resolvers
• If you want to write your own Operation Resolver -> take a look at Default Operation resolvers, they can fit your needs
• Via custom Operation Resolvers you can implement any Operation as you want -> store one object in multiple ContentProviders (why would you want to do that?), use custom sql things and so on

API of StorIOSQLite is same.