Field declarations should expose only the API needed.

[pixelzoom]

Noted when reviewing #59 , and for code review #41 ...

In IntroModel.ts:

  public readonly isShowingPredictMeanProperty: BooleanProperty;
  public readonly isShowingMeanProperty: BooleanProperty;
  public readonly isShowingTickMarksProperty: BooleanProperty;
  // Property that tracks whether auto-share is enabled or not.
  public readonly isAutoSharingProperty: BooleanProperty;

All of the above declarations should be Property<boolean>. There's nothing about the BooleanProperty subclass of Property<boolean> that needs to be exposed via the API. Instantiation using new BooleanProperty is correct.

This is not isolated to IntroModel.ts. I see this issue across many .ts files. Sorry I missed it during code review.

In general... The type used in the declaration of a field is not always the same type used when instantiating that field. Declarations should use the most general (narrowest API) type, and instantiation may be a more specific subtype. The same is true for method and function parameters.

Happy to discuss if this needs clarification.

[marlitas]

@zepumph helped me make sense of some of the type errors that came up when I tried this. I believe everything that could be converted has been converted, so sending over to @pixelzoom for a final look-over before closing.

[pixelzoom]

👍🏻 closing.