Web-capable Box API; based on IndexedDB

[greenrobot]

To support the Flutter Web platform, we need an alternative to native libraries, as wasm does not seem to cover everything the native libs do; e.g. "proper" file APIs.

To provide a minimal valuable implementation, implement the Box API using IndexedDB (and FlatBuffers similar to how we use it in the native side). No relations, indexes etc.

Once that works, open a ticket to do simple queries next.

[vaind]

Yes, that shouldn't be too hard to do. I've already thought about this a little a while back and how I've seen this done in Dart is:

• extract interfaces of the public APIs (Store, Box for now) instead of concrete classes
• have an implementation of those interfaces depending on the platform using conditional imports

[vaind]

Also a thing to consider: not all browsers support IndexedDB, so if we wanted to have a complete solution, we'll need (to do) something like https://pub.dev/packages/idb_shim

[greenrobot]

With like 97% of browsers supporting it we might be fine.

Another thing to consider: if we'd have the lower-level implemented in Type-/JavaScript, we could use that for plain web apps too. That probably makes sense when we start adding more features like queries.

[vaind]

Since this would require API changes (switch to interfaces) we should try to prepare those prior to 1.0, with the actual implementation coming later as a minor release.

[vaind]

if we'd have the lower-level implemented in Type-/JavaScript, we could use that for plain web apps too.

notes:

• to implement interaction with JavaScript (i.e. call a objectbox-js impelmentation from Dart) there's dart:js and package:js, looks like the latter supersedes the former. Regarding the performance of such an interop - couldn't find anything useful yet. From my understanding, there shouldn't be much cost to calling javascript, considering the rest of the dart code is compiled to javascript as well, maybe just some checks/data validations before crossing the boundary to the code generated by dart2js.
• there's no support to integrate dart with TypeScript (maybe except if you compiled your TS to JS but I don't know how that works), see this ancient Dart SDK issue.
• code written in Dart can be compiled to JS (dart2js), albeit at some size costs. From what I've read, Dart code compiled to JS should be faster than the "same" code in JS due to the optimizations Dart is able to do, e.g. because of its type system.

[greenrobot]

1. interfaces, yes. separate issue?

2. According to https://stackoverflow.com/a/26428441/551269, you may be able to call TypeScript just like JS. Would suggest a prototype.

[vaind]

you may be able to call TypeScript just like JS

As long as you write TypeScript just like JS, e.g. no generics (Box)

[vaind]

Turns out we don't actually need interfaces, just two variants of the concrete classes - the conditional import ensures the right implementation is imported. See #189

[greenrobot]

While we might not need interfaces (at least for now), it might be that we want them for the flexibility. Just tossing in that thought; more a discussion for later, I guess.

[Buggaboo]

I think that conditional is a compile-time thingy, it's not polymorphic dynamic binding.