Multiple constructor

[chungxon]

Hi, Thanks for the useful package!

I was just wondering if there was a way to make this package work with classes that have multiple constructors instead of the first available constructor or @MappableConstructor() annotaion. You can check out the similar feature in the Freezed package

[schultek]

Not multiple constructors, but you can do polymorphism like this: https://pub.dev/documentation/dart_mappable/latest/topics/Polymorphism-topic.html

[chungxon]

Hi @schultek

Thanks for your solution! For some reason, I think Freezed is better for me in this case, but I like your package for my coding style. I switched from Freezed to dart_mappable somewhere and will try it more in other use cases in the future.

If you can support multiple constructors, it will be very useful.

You can close this ticket.

[schultek]

I will keep it open as a feature request, but with low priority.

[MBulli]

Just want to add an code example because I have stumbled across this limitation as well. My code looked like this:

@MappableClass()
class Foo with FooMappable {
  final int? ident;

  final String? someData;
  final String? someDataOnlyForInsert;

  Foo.insert({
    required this.someData,
    required this.someDataOnlyForInsert
  }) : ident = null;

  Foo.update({
    required int this.ident,
    required this.someData,
  }) : someDataOnlyForInsert = null;
}

Basically, I have a DTO that represents an insert request or an update request. But in the encoded map the ident field is always missing.

[chungxon]

Hi @schultek never mind, I found a solution for this one. Anyone wants to implement multiple constructors like Freezed, you can refer to my example code below:

// Set the discriminator key to "type".
@MappableClass(discriminatorKey: 'type')
abstract class Animal with AnimalMappable {
  const Animal(this.name);

  // Factory constructors pointing to subclasses
  const factory Animal.nullAnimal(String name) = NullAnimal;

  const factory Animal.defaultAnimal(String name, String type) = DefaultAnimal;

  final String name;
}

// This sub-class will be chosen when the discriminator is null.
@MappableClass(discriminatorValue: null)
class NullAnimal extends Animal with NullAnimalMappable {
  const NullAnimal(super.name);
}

// This sub-class will be chosen on any unknown discriminator.
@MappableClass(discriminatorValue: MappableClass.useAsDefault)
class DefaultAnimal extends Animal with DefaultAnimalMappable {
  const DefaultAnimal(super.name, this.type);

  final String type;
}

[chungxon]

@schultek, I have created a PR #332 to add this example to the document. I would appreciate it if you could review it

You can close this issue. Thank you~