Add option to omit null fields in fromJson constructor or define default values

[AlexanderJohr]

Great Library. Finally something to replace Dartson with. However: When deserializing fields that aren't in the json, they will be written to the object as null. In Angular I then get errors like "boolean expression must not be null". I would like to keep the default values assigned to the fields instead of having those overwritten by null:

// Please keep my assigned value, don't overwrite with null
bool myBool = true

Or maybe setting the default value with an annotation would be useful.

@JsonKey(default: true)
bool myBool

[kevmoo]

@AlexanderJohr – FYI, going to look into this soon...

Something we want for other things. @jakemac53 FYI

[jakemac53]

+1 for an annotation, and possibly a warning if it sees a default value for a constructor parameter that it knows its going to overwrite with (possibly) null?

[AlexanderJohr]

Awesome!

[kevmoo]

Published, @AlexanderJohr – let us know how it goes...

[AlexanderJohr]

@kevmoo Works just great! Now I can remove all those factory constructors which ensured my default values before.

[kevmoo]

👍

[Nico04]

In my projects, several of my classes inherits this class :

abstract class Editable {
  DateTime updatedAt;

  Editable() : updatedAt = DateTime.now();
} 

The idea is to store the date when the objet was created.
It works great when a create objets from my code.
But if the objetc is created from a json (via fromJson), and because the json doesn't include updatedAt, updateAt is overriten with null, which is unwanted.

Setting the default value with @jsonkey(defaultValue: ...) is not enought because if the object is created not from a json, it doens't get his default value...

Any idea ?

[kevmoo]

@Nico04 – this is tough.

You could create get/set pairs with a private field and ignore null values on set to updatedAt.

[Nico04]

But what if I need this behavior globally for all my serializable classes?
Do not override a field with null in fromJson

[kevmoo]

@Nico04 – we're not going to run with this. It'd add a LOT of complexity to the generator to track this.

We're trying to keep things reasonably simple, especially if there is a work-around.

[Nico04]

I'm a bit disapointed but I totally understand your argument.
Thanks for answering so quickly though 👍

[Nico04]

It seems that now the package has a defaultValue key.
This is great, and it could solve this issue, but you have to set this for each fields and REPEAT default value which is not clean nor practicle.
Any plans on making it a global key please ?

[vihangel]

I think this can solve your problem

//when the variable has the value that match with the ignore json will not be constructed!

@jsonkey(ignore: null)
final String verificationCode;

https://docs.flutter.dev/development/data-and-backend/json