Support for Streams from query objects #88

Buggaboo · 2019-12-25T21:32:28Z

entity objects have changed, how did java/swift/go do this?

greenrobot-team · 2020-06-29T11:14:52Z

@Buggaboo Thanks. Chiming in here: similar to the other bindings (e.g. Java https://docs.objectbox.io/data-observers-and-rx#data-observers-basics) observers are meant to notify that there was a change to a box (not what has changed) or more importantly return updated query results if there was a change to a box.

The internal APIs only provide ways to listen that there was a change to a single box or all boxes, not which changes. The binding should then add wrapper code so the user can subscribe to e.g. the latest query results (if there was a change, re-run the query and return the new results). Again, see the Java binding for examples.
https://docs.objectbox.io/data-observers-and-rx#data-observers-basics

Hope this helps.

Buggaboo · 2020-07-15T13:01:14Z

@Buggaboo Thanks. Chiming in here: similar to the other bindings (e.g. Java https://docs.objectbox.io/data-observers-and-rx#data-observers-basics) observers are meant to notify that there was a change to a box (not what has changed) or more importantly return updated query results if there was a change to a box.

The internal APIs only provide ways to listen that there was a change to a single box or all boxes, not which changes. The binding should then add wrapper code so the user can subscribe to e.g. the latest query results (if there was a change, re-run the query and return the new results). Again, see the Java binding for examples.
https://docs.objectbox.io/data-observers-and-rx#data-observers-basics

Hope this helps.

Thanks, I'll look into it again, and try to follow the existing syntax.

All the callbacks and streams work as expected tho.

vaind

Only had a very quick look, will need to dive deeper and play with the code to understand it fully before reviewing properly.

vaind · 2020-07-17T11:18:43Z

lib/src/observable.dart

+  static final any = <int, Any>{}; // radix? > tree?
+
+  // sync:true -> ObjectBoxException: 10001 TX is not active anymore: #101
+  static final controller = StreamController<int>.broadcast();


Is that comment on an issue that needs looking at?

Yeah, that requires some attention

What does the reference of #101 mean here?

It was generated here, see nativeCode.
GitHub issue number was triggered.

lib/src/query/query.dart

vaind · 2020-07-17T11:23:26Z

README.md

+### Streams
+
+Streams can be created from queries.
+The streams can be extended with [rxdart](https://github.com/ReactiveX/rxdart);


Any reason why rxdart? Are there other alternatives you've considered?

It seems to be the most popular one, and it supports Stream which is more idiomatic, by way of extensions. I expose a stream property from an observable query for that reason.

greenrobot-team · 2020-07-28T06:43:52Z

@Buggaboo A general remark: please look at the Dart Analysis issues and resolve them if possible (e.g. compare to changes made to your last PR).

lib/src/observable.dart

lib/src/bindings/signatures.dart

…d of casting and/or declaring types

Pointer.asFunction complained that the typedef parameter was not proper.

lib/src/observable.dart

test/stream_test.dart

and there is no consensus on entity ids

…its own ViewModel/BLoC

lib/src/observable.dart

greenrobot-team · 2020-10-05T12:20:24Z

test/stream_test.dart

+    });
+
+    box.put(TestEntity(tString: 'Hello world'));
+    await Future.delayed(Duration(seconds: 0)); // ffi explodes without


The docs for Future.delayed contain

If the duration is 0 or less, it completes no sooner than in the next event-loop iteration, after all microtasks have run.

I don't know much about Dart, but this sounds like the observer callback is held up from executing while this "thread" is active. Might this cause issues in an actual app where the callback execution is held back too long? Is it possible to run them on a separate "thread" so they are not held up by other code?

Hm, reading the StreamController.broadcast docs on using sync is false mode (recommended) this actually sounds like expected behavior (events may be delivered at any point after the code adding the event has completed). LGTM then.

Maybe remove those ffi explodes without comments then and clarify regarding delayed event delivery.

I updated this.

example/flutter/objectbox_demo/lib/main.dart

greenrobot-team · 2020-10-05T12:42:47Z

example/flutter/objectbox_demo/lib/main.dart

+
+  void dispose() {
+    _query.close();
+    _store.unsubscribe();


I wonder if this should be part of close(). This feels like something very easy to forget.

It's called by close iirc. I didn't want to expose the BLoC/VM's internals to the Widgets. Leaky abstractions and such.

Oh, sorry, should have been more clear: was talking about not even exposing unsubscribe() to the user and doing it as part of close().

Good point.

greenrobot-team · 2020-10-05T12:48:37Z

@Buggaboo Thanks for your latest changes and 👍 for also improving our example app! I had some more questions, but this LGTM now.

@vaind Can you look at observable.dart and check if using store.prt as user_data when creating an observer is fine? My knowledge is lacking there. (Note: is on holiday, so this might take a while.)

greenrobot-team · 2020-10-05T12:53:26Z

Sorry, forgot one thing: look at Dart Analysis issues and run the formatter.

greenrobot-team · 2020-10-13T08:43:11Z

Squashed and merged. I fixed the analysis and formatting issues myself (0a941a5).

Thanks again.

vaind · 2020-10-21T05:58:42Z

@vaind Can you look at observable.dart and check if using store.prt as user_data when creating an observer is fine? My knowledge is lacking there. (Note: is on holiday, so this might take a while.)

Should be fine to the best of my knowledge.

Buggaboo added 4 commits December 25, 2019 20:44

callbacks from C work

3ed735f

clean up

8a6bc25

Merge branch 'dev' into feature/future-stream

502edad

fixed tests, now using futures

a5d177e

Buggaboo force-pushed the feature/future-stream branch from e7e2e87 to a5d177e Compare May 17, 2020 01:11

Buggaboo changed the title ~~WIP - Added support for _obx_observe_ and _obx_observe_single_type_~~ WIP - Added support for obx observers (single and multiple types) May 17, 2020

Buggaboo changed the title ~~WIP - Added support for obx observers (single and multiple types)~~ WIP - Added support for obx observers (1 & >1 types) May 17, 2020

Callbacks are pretty useless if we don't know which

372de28

entity objects have changed, how did java/swift/go do this?

Buggaboo mentioned this pull request May 22, 2020

How to implement observers to return changed objects? #104

Closed

Buggaboo changed the title ~~WIP - Added support for obx observers (1 & >1 types)~~ Help needed - Added support for obx observers (1 & >1 types) May 24, 2020

Buggaboo changed the title ~~Help needed - Added support for obx observers (1 & >1 types)~~ Help required - Added support for obx observers (1 & >1 types) May 24, 2020

Buggaboo changed the title ~~Help required - Added support for obx observers (1 & >1 types)~~ Help required: Support for obx observers May 24, 2020

Buggaboo added 4 commits July 16, 2020 15:33

Merge branch 'dev' into feature/future-stream

f19c4e2

Some Stream tests won't work without an 'await', ffi blows up

bd6f3ee

All the callbacks and streams work as expected tho.

improve sub and unsub behavior

70a038c

update readme for streams

b3e5fda

Buggaboo changed the title ~~Help required: Support for obx observers~~ Support for obx observers Jul 17, 2020

Buggaboo changed the title ~~Support for obx observers~~ Support for dart Streams from query objects Jul 17, 2020

Buggaboo changed the title ~~Support for dart Streams from query objects~~ Support for Streams from query objects Jul 17, 2020

vaind changed the base branch from dev to main July 17, 2020 10:34

vaind reviewed Jul 17, 2020

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removed double quotes, also unnecessary "this"

113fb55

greenrobot-team reviewed Aug 3, 2020

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Buggaboo added 3 commits September 24, 2020 18:44

removed superfluous extraneous redundant parameterized typedefs

3a6184d

Merge branch 'main' into feature/future-stream

0c79ef0

double quotes to single

e00bdfd

Buggaboo added 2 commits September 26, 2020 21:56

specified the types properly for the compiler on obj creation, instea…

2a4c6f8

…d of casting and/or declaring types

Code duplicated for the sake of shutting up a lint false positive:

80b1256

Pointer.asFunction complained that the typedef parameter was not proper.

Buggaboo mentioned this pull request Sep 26, 2020

Box insert - assign new IDs on passed objects #62

Closed

greenrobot-team reviewed Sep 28, 2020

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Buggaboo added 7 commits September 28, 2020 16:23

fix in case single observer for multiple stores

6aacbf9

and there is no consensus on entity ids

applied stream to demo app and flattened the code a bit

5d69ebf

the sync tests just required more Future.delayed(... 0))

3c9698f

forgot to close the query

b3483ed

package private fields

63600bb

replaced listener with StreamBuilder, extracted database plumbing to …

e62ad2a

…its own ViewModel/BLoC

oopsie

cd4a391

greenrobot-team reviewed Oct 5, 2020

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greenrobot-team reviewed Oct 5, 2020

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greenrobot-team reviewed Oct 5, 2020

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Buggaboo and others added 2 commits October 5, 2020 23:13

changed comments to just declaring something explodes

298169e

Merge branch 'main' into feature/future-stream

c32df43

greenrobot-team merged commit 164a646 into objectbox:main Oct 13, 2020

greenrobot-team added this to the 0.8 milestone Oct 13, 2020

greenrobot-team added the enhancement New feature or request label Oct 13, 2020

Buggaboo deleted the feature/future-stream branch October 13, 2020 13:43

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Support for Streams from query objects #88

Support for Streams from query objects #88

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Support for Streams from query objects #88

Support for Streams from query objects #88

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