fix: flutter web identify getAnonymousId error.

[keepwa1king]

1. I found that Posthog().identify not works in Flutter web. The reason is calling distinctId. So I changed distinctId to userId.
2. I found that Posthog().getAnonymousId not works in Flutter web. It makes error like this.

Error: PlatformException(error, NoSuchMethodError: 'user'
method not found
Receiver: Instance of 'NativeJavaScriptObject'
Arguments: [], null, null)

In posthog-js, getting the anonymous Id is able to call the method "get_distinct_id". So, I changed the code to call method "get_distinct_id".

https://posthogusers.slack.com/archives/CT7HXDEG3/p1624946446377900

I sended at Slack about the error.

[fuziontech]

Thank you so much for the PR! Nice catch on the get_distinct_id call.

Can you try passing your userId as distinctId parameter in identify to see if that works?

[fuziontech]

I think keeping it as distinctId keeps it aligned with our JS library
https://github.com/PostHog/posthog-js/blob/master/src/posthog-core.js#L810

Have you tried passing your userId as the distinctId parameter?

[keepwa1king]

@fuziontech
Thank you for giving me a feedback!
I changed distinctId to userId because of the default setting of Posthog().identify.
To use Posthog().identify, there is a required parameter "userId".
So I have to use like this.

Posthog().identify(userId: "Shinyoung Tyga Lee");

I think that using distinctId should make change about default setting of required parameter "userId" name.

[fuziontech]

You are totally right!

posthog-flutter/lib/src/posthog.dart

Line 19 in 7beff56

required userId,

Your changes look great and make this more consistent.

[fuziontech]

Nice! Great catch here :)

[fuziontech]

Changes look good!

[keepwa1king]

Thank you!

[fuziontech]

No prob! give 2.0.3 a try to make sure everything is working 👍