Custom typeFn for date strings?

[calvinwyoung]

A common use case we have for automapper is converting Date objects into date strings (i.e., YYYY-MM-DD). Right now we're applying a dateToStringConverter to each date field as described in the docs. This works fine, but is very verbose when working with a lot of date properties.

We'd love to be able to define a DTO like this:

export class FooDto {
  @AutoMap({ typeFn: () => DateString })
  date?: DateString;
}

This could use a custom DateString type that could look something like this:

export class DateString extends String {
  constructor(value: unknown) {
    super(formatAsDateString(value));
  }
}

(This specific implementation is admittedly gross — I'm just riffing on the @AutoMap({ typeFn: () => String }) pattern that's common for string enums.)

Is there way to implement something similar with automapper? Ideally we'd like to use the same pattern to convert any type of non-JSON-serializable object to strings.

[micalevisk]

what about custom type converters?

[calvinwyoung]

The issue with that approach is that sometimes we want to map a Date object to an ISO timestamp string (e.g., 2000-01-01T01:00:00.000Z) and other times we want to map it to a date string (e.g., 2000-01-01). In both cases, the mapping is from Date -> string

Is there a way to implement a custom type converter that can distinguish between these two cases?

[micalevisk]

oh, got it.

Is there a way to implement a custom type converter that can distinguish between these two cases?

I guess not.

[micalevisk]

can you show how you're using ConvertUsing?

[calvinwyoung]

@nartc Happy new year! Just wanted to see if you had a sense for when you might be able to relax the return types for the converter function. We're still using the above workaround but it'd be nice to remove it if possible. Thank you!

[nartc]

@calvynwyoung Happy new year to you too! I'll release it tomorrow. Tbh, I forgot about this as it's marked Answered 😄

[calvinwyoung]

🤣 No problem at all! Thanks for the quick turnaround!

[nartc]

@calvinwyoung 7.2.1 has been released with relaxed type

[calvinwyoung]

This works beautifully! Thank you!!