alexeyinkin commented on code in PR #24957:
URL: https://github.com/apache/beam/pull/24957#discussion_r1131041017
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learning/tour-of-beam/frontend/lib/locator.dart:
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@@ -61,3 +64,12 @@ void _initializeState() {
),
);
}
+
+void _initializeServices() {
+ final googleAnalyticsService = GoogleAnalytics4Service(
+ propertyId: kAnalyticsUA,
+ );
+ GetIt.instance.registerSingleton<AnalyticsService>(
+ googleAnalyticsService,
+ );
Review Comment:
Although the analytics classes are inside the shared `playground_components`
package, the instantiation of the service is external to it. This gives us the
future flexibility to:
1. Change the implementations for Playground and ToB independently.
2. Write tests that mock the analytics service.
3. Use the shared Playground widgets in a new app that does not send
analytics data by registering a null-object for analytics.
There are a number of ways to implement this:
1. Wrap Playground widgets in a `Provider` widget to provide them with a
specific analytics service. But this gives no compile-time guarantee that the
provider is in the tree and leads to bugs.
2. Use a service locator of which `get_it` is the most popular one. So we
did.
> It isn't clear from this what is actually implementing the abstract
AnalyticsService class without some digging.
We need easy swap to a potential `SomethingElseAnalyticsService`, so this
abstraction is on purpose. We could register the service to be read as
`get<GoogleAnalyticsService>()`, but then swapping would affect dozens of
locations.
The promise `get_it` gives is that widgets no longer have to reference
global variables or rely on `Provider`s. And this promise is fulfilled.
`Provider` leads to even more digging while global variables bar the 3
opportunities above.
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