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feat(dialog): Dialogs can define the type for their dialog data #23985
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I very much like the idea.
It is used like this:
and then we pull the inner marker type out of all the constructor parameters. We grap the return type of the dialog in the very same way ( In the end our implementation looks like this:
One further pro of this solution is that it should be backwards compatible because if the marker type is not used, then the type could still be inferred as any. |
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I really like this idea. It will allow to just pass the component and get type safety for data and result. Even better if the dialog has no data or no result this can be type checked too. |
Feature Description
#4398 introduced a generic type argument for
MatDialogConfig
. This type argument is forwarded inopen
. However, the type is never tied in anyway to the actual component, making the type argument an essentially useless type assertion.While due to the nature of Angular's dependency injection full type-safety cannot be achieved, it would be nice if at least the dialog component could declare the type it receives itself in such a way that a call to
open
will infer the correct type automatically. In order to achieve this, the dialog component needs to somehow expose this information. Here are a few possible solutions in no particular order, though others might exist:Interface with type inference
We could define an interface and a helper type as follows:
We can then adjust the type signature of
open
to infer the type accordingly:Finally, a dialog component would be required to have a public field named
data
of the according type, which would typically be achieved through the injection itself:Note: This change is breaking because the generic signature of
open
changes and because dialog components could have an unrelateddata
field which would lead to an unintended type inference. Unfortunately we cannot prevent this here due to TypeScript's structural typing nature. In particular users would no longer be able to manually define the generic type argument. However see further below for a solution to this problem.Interface with explicit method
Instead, we could also introduce an interface with an explicit method to be implemented:
Otherwise the approach is largely similar. This change is only breaking in the generic type signature (I'm not sure whether you count this as a breaking change), however we could actually avoid that by changing our helper type to
and then using the type argument as a fallback:
Note: The same could be done in the solution above. I believe we could make this a completely backwards-compatible change, excluding of course the exotic situation that a component happens to already have a
getDialogData
method for unrelated reasons. The only disadvantage here is forcing the component to provide a public method. In practice I don't consider this a concern as Angular already forces us to make many things public that shouldn't be public from a component API perspective.On a very similar note, it would be nice to have the same for the inferred result type
R
, i.e. the component being able to define the type of data it can return, and have this information flow through theopen
method to the caller. The approaches mentioned above could, in theory, cover this as well.Use Case
Given some
MyDialogComponent
which expects dialog data of typeMyDialogData
, I would liketo type-check
data
againstMyDialogData
without having to manually specifyopen
's type arguments, but rather have this information flow fromMyDialogComponent
.The text was updated successfully, but these errors were encountered: